Secular trends of age at menarche and age at menopause in women born since 1951 from a county of Shandong Province, China / 北京大学学报(医学版)

OBJECTIVE@#To describe the secular trends of age at menarche and age at natural menopause of women from a county of Shandong Province.@*METHODS@#Based on the data of the Premarital Medical Examination and the Cervical Cancer and Breast Cancer Screening of the county, the secular trends of age at menarche in women born in 1951 to 1998 and age at menopause in women born in 1951 to 1975 were studied. Joinpoint regression was used to identify potential inflection points regarding the trend of age at menarche. Average hazard ratios (AHR) of early menopause among women born in different generations were estimated by performing multivariate weighted Cox regression.@*RESULTS@#The average age at menarche was (16.43±1.89) years for women born in 1951 and (13.99±1.22) years for women born in 1998. The average age at menarche was lower for urban women than that for rural women, and the higher the education level, the lower the average age at menarche. Joinpoint regression analysis identified three inflection points: 1959, 1973 and 1993. The average age at menarche decreased annually by 0.03 (P < 0.001), 0.08 (P < 0.001), and 0.03 (P < 0.001) years respectively for women born during 1951-1959, 1960-1973, and 1974-1993, while it remained stable for those born during 1994-1998 (P=0.968). As for age at menopause, compared with women born during 1951-1960, those born during 1961-1965, 1966-1970 and 1971-1975 showed a gradual decrease in the risk of early menopause and a tendency to delay the age at menopause. The stratified analysis presented that the risk of early menopause gradually decreased and the age of menopause showed a significant delay among those with education level of junior high school and below, but this trend was not obvious among those with education level of senior high school and above, where the risk of early menopause decreased and then increased among those with education level of college and above, and the corresponding AHRs were 0.90 (0.66-1.22), 1.07 (0.79-1.44) and 1.14 (0.79-1.66).@*CONCLUSION@#The age at menarche for women born since 1951 gradually declined until 1994 and leveled off, with a decrease of nearly 2.5 years in these years. The age at menopause for women born between 1951 and 1975 was generally delayed over time, but the trend of first increase and then decrease was observed among those with relatively higher education levels. In the context of the increasing delay in age at marriage and childbearing and the decline of fertility, this study highlights the necessity of the assessment and monitoring of women' s basic reproductive health status, especially the risk of early menopause.

Thyroid function of first-trimester twin pregnant women and its association with preterm delivery / 北京大学学报(医学版)

OBJECTIVE@#To describe the thyroid function abnormality of first-trimester twin pregnant women according to different references, and to explore its association with preterm delivery.@*METHODS@#Participants, first-trimester twin pregnant women, were recruited at Peking University Third Hospital from March 2017 to February 2020. The thyroid hormone reference for ordinary adults identified on the assay kits by Siemens incorporation, thyroid hormone reference specifically for singleton pregnancy established previously, and thyroid hormone reference specifically for twin pregnancy established previously were used in the description of hypothyroidism and hyperthyroidism for first-trimester twin pregnant women. Thyroid autoantibody reference identified on the assay kits by Siemens incorporation was used in the description of positive thyroid autoantibody. Multivariable log-binomial regression was conducted to examine the association between thyroid function and preterm delivery, in which normal pregnant women according to the three references and normal pregnant women according to twin pregnancy reference accompanied with negative thyroid autoantibody were taken as control respectively.@*RESULTS@#A total of 570 twin pregnant women were finally included. Rates of hypothyroidism according to the three references were 1.2%, 1.6% and 3.5%, respectively. Rates of hyperthyroidism according to the three references were 32.6%, 18.1% and 1.1%, respectively. After adjustment for potential confounding factors, risk of preterm delivery significantly increased in pregnant women with hyperthyroidism according to the twin specific pregnancy reference [adjusted relative risk (ARR)=1.41, 95%CI: 1.14-1.75], while no significant increase was found in those with normal thyroid function according to the twin specific pregnancy reference but hyperthyroidism according to the singleton specific pregnancy reference (ARR=1.00, 95%CI: 0.81-1.25) and in those with hyperthyroidism purely according to the ordinary adult reference (ARR=1.06, 95%CI: 0.85-1.32), compared with those normal according to all the references. Risks of preterm delivery almost significantly or significantly increased in pregnant women with hypothyroidism according to the ordinary adult or singleton specific pregnancy reference (ARR=1.40, 95%CI: 0.88-2.22) and those with hypothyroidism according to the twin specific pregnancy reference (ARR=1.53, 95%CI: 1.03-2.28). Overall analysis of thyroid function according to the twin specific pregnancy reference and thyroid autoantibody showed that risks of preterm delivery almost significantly or significantly increased in pregnant women with simple hypothyroidism (ARR=1.46, 95%CI: 0.93-2.27), simple positive thyroid autoantibody (ARR=1.32, 95%CI: 1.15-1.52), and hypothyroidism accompanied with positive thyroid autoantibody (ARR=1.78, 95%CI: 1.30-2.44), compared with those normal according to the twin specific pregnancy reference with negative thyroid autoantibody.@*CONCLUSION@#The ordinary adult reference and that of singleton pregnancy may lead to under-diagnosis of hypothyroidism and over-diagnosis of hyperthyroidism in first-trimester twin pregnant women. Compared with pregnant women with normal thyroid function, those missed in the diagnosis of hypothyroidism were at a higher risk of preterm delivery, while those over-diagnosed as hyperthyroidism had a similar risk of preterm delivery, indicating a need to develop and generalize twin-pregnancy-specific reference on common indicators of thyroid function. Moreover, the thyroid autoantibody should be taken into consideration in the prenatal diagnosis and treatment to twin pregnant women with hypothyroidism.

Relationship of plasma vitamin A levels between neonates and pregnant women in third trimester / 北京大学学报(医学版)

OBJECTIVE@#To study the correlation of plasma vitamin A (VitA) levels between neonates and pregnant women in third trimester.@*METHODS@#A total of 688 pregnant women were recruited in Yuanshi and Laoting counties of Hebei Province, from May to June 2009. Venous blood samples of women before delivery and cord blood samples of newborns were collected and measured for retinol (retinol concentration was used to reflect VitA level) using high performance liquid chromatography assay. According to venous blood plasma retinol concentration, maternal VitA nutritional status was divided into deficiency (<0.70 μmol/L), marginal deficiency (0.70-<1.05 μmol/L), and sufficiency (≥1.05 μmol/L). According to cord blood plasma retinol concentration, neonatal VitA nutritional status was divided into deficiency (<0.35 μmol/L), marginal deficiency (0.35-<0.70 μmol/L), and sufficiency (≥0.70 μmol/L); neonatal VitA relative deficiency was further defined as cord blood plasma retinol concentration lower than the 10th percentile. VitA placental transport ratio was defined as retinol concentration in the neonates divided by that in pregnant women. Multivariable fractional polynomials (MFP) model and Pearson correlation were used to study the dose-response relationship between maternal and neonatal plasma VitA levels, Logistic regression model to estimate the effect of maternal VitA nutritional status on neonatal VitA deficiency, and MFP model and Spearman correlation to describe the relationship between maternal VitA level and VitA placental transport ratio.@*RESULTS@#The average retinol concentration of the pregnant women was (1.15±0.30) μmol/L, and the prevalence of VitA deficiency and marginal deficiency were 4.5% and 37.8%, respectively. Average retinol concentration of the neonates was (0.78±0.13) μmol/L, and no neonates were VitA deficiency, 28.2% of the neonates were marginal deficiency. After multivariable adjustment, the VitA level of the neonates was positively and linearly related to maternal VitA level (pm=1, P<0.05), with the corresponding Pearson correlation coefficient of 0.13 (P<0.01). As compared with the women with sufficient VitA, those with VitA deficiency (crude OR=2.20, 95%CI:1.04-4.66) and marginal deficiency (crude OR=1.43, 95%CI:1.01-2.02) had higher risks to deliver neonates with VitA marginal deficiency; while the risks turned to be non-significant after multivariable adjustment. The pregnant women with VitA deficiency had higher risk to deliver neonates with relative VitA deficiency before and after multivariable adjustment (crude OR=3.02, 95%CI:1.21-7.50; adjusted OR=2.76, 95%CI:1.05-7.22). The maternal VitA level was negatively and non-linearly correlated with placental transport ratio (pm= -0.5, P<0.05), with corresponding adjusted Spearman correlation coefficient of -0.82 (P<0.001).@*CONCLUSION@#There was a positive linear dose-response relationship between VitA levels of newborns and pregnant women in third trimester, indicating that neonatal VitA storing levels at birth was affected by maternal VitA nutritional status.

Mobile terminal-based survey on the birth characteristics for Chinese newborns / 北京大学学报(医学版)

OBJECTIVE@#To describe the birth characteristics for Chinese newborns, to assess the feasibility of collecting basic data on maternal and child health, and to conduct relevant epidemiological studies by using mobile terminals.@*METHODS@#From June 2016 to January 2017, pregnant women who delivered in hospitals were recruited in 166 hospitals scattered across 23 provinces of China. The data on their maternal and child health including delivery mode, gestational age and birth weight, were collected by self-administered questionnaires embedded in a mobile application. The incidences or means of cesarean section, preterm birth, birth weight, length and head circumference were calculated and compared with recognized national data, including 2005 Growth Standards for Chinese Children Under 7 Years of Age, 2006 World Health Organization Child Growth Standards and 2014 Chinese Neonatal Birth Weight Standards by Gestational Age.@*RESULTS@#A total of 9 986 women were investigated, among whom those aged ≥35 years accounted for 11.7% and those received well education (college and above) accounted for 70.2%. The rate of cesarean section, preterm delivery, low birth weight and macrosomia were 38.1%, 4.5%, 2.2%, and 7.8%, respectively. The means were (3.33±0.44) kg [male (3.36±0.44) kg, female (3.29±0.43) kg] for birth weight, (50.97±2.32) cm [male (51.04±2.32) cm, female (50.89±2.32) cm] for birth length, and (33.99±1.56) cm [male (34.01±1.57) cm, female (33.97±1.55) cm] for head circumference, respectively. As compared with the national data, the cesarean section rate and birth weights by gestational age for term-born neonates were similar to the latest national data in 2014, while the means of birth weight and length were obviously higher than those of the 2005 Growth Standards for Chinese Children Under 7 Years of Age and 2006 World Health Organization Child Growth Standards.@*CONCLUSION@#As compared with the national data 10 years ago, the mean birth weights for male and female newborns were increased by 40 g and 80 g respectively and mean lengths by 0.6 cm and 1.3 cm, but changes for mean head circumferences were negligible, indicating that the physical health condition for Chinese newborns improved significantly over past 10 years and emerging information technology likely provided a new approach for epidemiological research.

Melamine Nephrotoxicity is Mediated by Hyperuricemia / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>We tested whether melamine nephrotoxicity was exacerbated by urate (a typical component of renal stones in humans) in rats with hyperuricemiainduced by the uricase inhibitor, potassium oxonate (Oxo).</p><p><b>METHODS</b>Rats were exposed to melamine or Oxo alone or combinations of melamine (200-400 mg/kg) and Oxo (200-600 mg/kg) for 3 consecutive days. Kidney injury was evaluated by renal biochemical functions, histomorphology, and lipid peroxidation. Kidney crystals were analyzed for their composition.</p><p><b>RESULTS</b>Nephrotoxicity was minimal in animals administered melamine or Oxo alone, but it was demonstrable in animals administered at least 800 mg/kg of the two compounds combined. All rats in the 400+600 (melamine+Oxo) and 400+400 mg/kg groups and 4 out of 6 in the 200+600 mg/kg group died within 3 days; no rat died in the 200+400 or 200+200 mg/kg group. Dose-dependent renal damage resembling clinical findings in affected patients was observed in rats administered the two compounds. Crystal composition determination revealed the existence of melamine and uric acid in the affected kidneys, resembling human stones.</p><p><b>CONCLUSION</b>Our findings suggest that uric acid plays a key role in melamine-related kidney injury in humans. Future studies should consider uric acid together with melamine when examining adverse effects in humans.</p>

Folate status in the red blood cell and related geographical differences among 810 with 65- to 74- year-old population of two counties in Southern and Northern China / 中华流行病学杂志

Objective To assess the red blood cell (RBC) folate status among Chinese elderly population and its geographical differences between Southem and Northern regions,and to evaluate the correlation between RBC and plasma folate.Methods This study was conducted in two counties of Jiangsu and Hebei provinces of China.A total of 810 individuals aged 65-74 years were recruited.RBC folate in blood samples was measured by microbiological assay.Data on RBC folate was log-transformed before analysis.Means of RBC folate concentration were compared by t-test,and the prevalence rates of RBC folate deficiency for different characteristics were compared by x2 test.Results The geometric mean ofRBC folate concentration was 1083.3 nmol/L(95％CI:1034.11134.8) among the Southerners and 489.1 nmol/L (95％CI:466.7-512.6) among the Northerners,with the former being 2.2 times of the latter (t=23.684,P＜0.001 ).The prevalence rates of RBC folate deficiency were 1.0％ in the South and 28.9％ in the North (x2=124.06,P＜0.001).The concentrations of RBC folate were positively correlated with plasma folate (r=0.49,P＜0.001 ).After adjustment for region,sex,age,BMI,education,exposure to tobacco smoking and alcohol consumption,the correlation remained significant (r=0.38,P＜0.001 ).Conclusion In 810 Chinese elderly population aged 65-74 from the two counties,Southerners had a higher RBC folate concentration and a lower deficiency prevalence than those in the Northerners.The RBC folate concentration was positively associated with plasma folate.

Impact of pregnancy terminations before 28 weeks of gestation on the overall prevalence of neural tube defects in two counties of Shanxi province / 中华流行病学杂志

Objective To examine the impact of pregnancy termination before 28 weeks of gestation on the overall prevalence of neural tube defects (NTDs).Methods Data collected during the period of 2004 and 2010 from a birth defects surveillance system in Pingding county and Talgu county of Shanxi province were used.Number of births ≥28 weeks of gestation and number of cases with major birth defects among the births were collected.Terminations of pregnancies before 28 weeks of gestation due to prenatal diagnosis were also collected.The total prevalence of neural tube defects,prevalence before 28 weeks of gestation,and prevalenee of ≥28 weeks gestation were calculated using the total number of pregnancies of ≥28 weeks of gestation as denominator.The prevalence data were compared to examine the impact of pregnancy termination on the total prevalence.The proportions of pregnancy terminations before 28 weeks of gestation due to prenatal diagnosis of an NTD against the total number of NTD cases were also calculated.Results During 2004-2010,52 366 births were recorded,and 485 NTD cases were ascertained.The overall prevalence of NTDs was 92.6 per 10 000 births,with prevalence of ＜28 weeks gestation due to pregnancy terminations as 60.9 per 10 000 births,while the prevalence of ≥28 weeks of gestation was 31.7 per 10 000 births.NTD prevalence of ≥28 weeks gestation was 66.0％ lower than the total NTD prevalence.In the last two years,the proportion of NTDs ascertained ≥28 weeks gestation accounted for about 40.0％ of the total NTD cases.Conclusion A birth-defect-surveillance program that covered only tregnancies ≥28 weeks of gestation resulted in a severe underestimation of the total birth prevalence of NTDs,especially for anencephaly.We would recommend that the current national birth defects surveillance system should include pregnancy terminations before 28 weeks of gestation and the calculation of total NTD prevalence should also include these cases into the numerator,so as to better estimate true population NTD prevalence,upon which the related public health policy is based.

Status of plasma folate in the third trimester of pregnant women and newborn babies in the northern rural areas of China / 中华流行病学杂志

Objective To study the plasma folate concentrations in the third trimester of pregnant women and newborn babies so as to assess the association between them.Methods Pregnant women in Yuanshi and Laoting counties in Hebei province from May to June in 2009 were recruited with related information collected at enrollment.Those pregnant women being enrolled were followed up until delivery.Maternal blood was collected before delivery,and cord blood was collected after the expulsion of the placenta.Data from 437 pairs of women and newborns were analyzed.Plasma folate concentration was measured by Microbiological assay,with maternal plasma folate concentration ＜6.8 nmol/L defined as folate deficiency.Neonatal plasma folate concentration below 10％ was defined as relative deficiency.Student t-test and ANOVA were used to compare the plasma folate concentrations between the groups and x2 test was used to compare the situation of folate deficiency.In order to assess the association between maternal and newborn folate levels,logistic regression analysis was used to estimate the odds ratio of the neonatal plasma folate relative deficiency between the maternal folate deficient and normal groups after adjusting factors as age,BMI,region,career and education.Linear regression was used to test the trend by quintiles of maternal plasma folate concentration.Pearson' s test was used to test the relationship between the ratio of neonatal and maternal plasma folate level and the level of maternal plasma folate.Results The geometric mean of maternal plasma folate concentration was 8.0(95％CI:7.6-8.5) nmol/L and the deficiency was 29.3％,but in newborn babies,they were 24.0(95％CI:23.1-25.0) nmol/L and 0.9％ respectively.The plasma folate level in newborn babies was 3.0 times as high as in maternal (t=32.519,P＜0.01 )but the neonatal plasma folate deficiency status was higher than in matemal ( x2=137.2,P＜0.01 ).When compared with the normal plasma folate level group,the risk on neonatal plasma folate relative deficiency in the maternal folate deficiency group was significantly higher aiter adjusted for confounders (OR=1.96,95％CI:1.02-3.80).The neonatal plasma folate level significantly increased along with the maternal plasma folate level (Ptrend＜0.05).The ratio of neonatal and maternal plasma folate level was significantly inversely correlated with the maternal folate level (r=-0.810,P＜0.001 ).Conclusion Folate status in newborns was much better than in their mothers',in the northern rural areas of China.The maternal folate status was positively correlated with their offspring' s.Active placental transport for folate was significantly increasing when the maternal plasma folate level decreased.

Maternal periconceptional consumption of pickled vegetables and risk of neural tube defects in offspring / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Maternal exposure to nitrate, nitrite, and N-nitroso compounds from drinking water or diet has been associated with an increased risk of neural tube defects (NTDs) in some studies. Pickled vegetables contain relatively large amounts of nitrite and N-nitroso compounds. We examined the association between maternal periconceptional consumption of pickled vegetables and NTDs in Shanxi Province of northern China.</p><p><b>METHODS</b>Data were derived from a population based case-control study of major external birth defects in four counties of Shanxi Province. Participants included 519 NTDs cases identified between 2003 and 2007 and 694 healthy controls. Exposure information was collected within 1 week after delivery. Multivariable non-conditional Logistic regression model was used to estimate the adjusted odds ratio (OR) controlling for potential confounding variables.</p><p><b>RESULTS</b>The risk of NTDs was positively associated with the frequency of the consumption of pickled vegetables by the mother. Compared with pickled vegetables consumption at < 1 meal/week, the adjusted OR for consumption at 1 - 3, 4 - 6, and > 6 meals/week were 1.3 (95% confidence interval (CI): 1.0, 1.8), 1.9 (1.1, 3.2), and 3.6 (1.9, 6.9), respectively. A protective effect was found for maternal meat consumption at ≥ 1 meal/week (adjusted OR: 0.6, 95%CI: 0.4, 0.7) and egg or milk consumption at ≥ 1 meal/week (adjusted OR: 0.6, 95%CI: 0.4, 0.8).</p><p><b>CONCLUSION</b>Maternal periconceptional consumption of pickled vegetables may increase the risk for NTDs in Shanxi Province.</p>

Cesarean delivery on maternal request and childhood intelligence: a cohort study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Cesarean section births have been steadily increasing over the past decade and have become an epidemic in China. Cesarean delivery on maternal request is a major contributor to this upward trend, and there has been of much concern about its impact on maternal and child health. Most of mothers believe that cesarean delivery on maternal request can improve the child's intelligence, but direct evidence is sparse. In this cohort study, we aimed to directly assess the impact of cesarean delivery on maternal request on childhood intelligence.</p><p><b>METHODS</b>Intelligence quotient (IQ) of 4144 preschool children from 21 cities/counties of Zhejiang and Jiangsu province whose mothers were registered in a population-based perinatal surveillance program during 1993-1996 was assessed with Chinese Wechsler Young Children Scale of Intelligence (C-WYCSI) in 2000. The outcomes were full-scale IQ, verbal IQ, and performance IQ of C-WYCSI. Mode of delivery and covariates were obtained from the surveillance program. We estimated unadjusted and adjusted effects of cesarean delivery on maternal request and assisted vaginal delivery on IQ scores compared with spontaneous vaginal delivery using regression analysis.</p><p><b>RESULTS</b>The mean full-scale, verbal, and performance IQ for all children was 99.3 ± 16.1, 93.6 ± 17.7, and 105.3 ± 14.3. In crude analysis, cesarean delivery on maternal request versus spontaneous vaginal delivery was associated with an increase of 3.9 (95% confidence interval, 0.6 to 7.2) points in full-scale IQ, 4.8 (1.2 to 8.4) points in verbal IQ, and 2.4 (-0.6 to 5.3) points in performance IQ. After adjusting for maternal education, occupation, and IQ, the advantage was reduced to 1.6 (-1.3 to 4.5), 2.3 (-0.8 to 5.5), and 0.6 (-2.0 to 3.3) points for full-scale, verbal, and performance IQ, respectively. Assisted vaginal delivery versus spontaneous vaginal delivery was not associated with IQ scores in any analysis.</p><p><b>CONCLUSION</b>Neither cesarean delivery on maternal request nor assisted vaginal delivery affected children's IQ.</p>

Prospective cohort study of pregnancy-induced hypertension and risk of preterm delivery and low birth weight / 中华预防医学杂志

<p><b>OBJECTIVE</b>To determine the association between pregnancy-induced hypertension(PIH) and risk of preterm delivery (PD) and low birth weight (LBW).</p><p><b>METHODS</b>A prospective cohort was established based on 131 867 women who delivered a singleton baby in seven cities or counties in Zhejiang province, China, during the period of 1995 - 2000. The exposure group included 14 278 women who were diagnosed as PIH, and the non-exposure group included 117 589 women. The exposure group was divided into mild, moderate, and severe subgroups based on the severity of PIH, and further divided into early, medium and late onset subgroups based on the time of onset of PIH (occurred in second trimester, third trimester, or during delivery). The primary outcome measures were the incidence of PD and LBW. Multiple logistic regression was used to estimate relative risk and 95% confidence intervals after adjustment by maternal age, occupation, education, parity, number of prenatal visits, gestational disease, caesarean delivery, pregnant body mass index, fetal sex, and gestational age (only for LBW).</p><p><b>RESULTS</b>The incidence rates of PD and LBW in exposure group were 4.9% (701/14 278) and 3.6% (507/14 278), and both rates were higher than those of the non-exposure group (3.4% (4031/117 589), 1.8% (2110/117 589)) (chi(2) values were 80.8 and 202.0, P < 0.001). The incidence rates of PD in mild, moderate, and severe subgroups were 3.9% (404/10 358), 5.8% (181/3099), and 14.1% (116/821), and corresponding incidence rates of LBW were 2.5% (258/10 358), 4.9% (151/3099), and 11.9% (98/821). Both rates were increased with the severity of PIH (chi(2) values were 196.4 and 426.1, P-value for trend < 0.001). The incidence rates of PD in early, medium, and late onset subgroup were 8.4% (50/598), 5.7% (278/4867), and 4.2% (373/8813), and corresponding incidence rates of LBW were 5.7% (34/598), 4.2% (206/4867), and 3.0% (267/8813). Both rates were decreased by the time of PIH onset (chi(2) values were 115.4 and 239.8, P-value for trend < 0.001).</p><p><b>CONCLUSION</b>PIH could increase the incidence of PD and LBW.</p>

Introduction to an individual-based standardization method-propensity score weighting / 中华流行病学杂志

In this article,we presented the rationale and calculation procedures of a propensity score weighting method,with its application in epidemiological studies.The rationale for propensity score weighting method is similar to those for traditional standardization methods.Propensity score is used to estimate the weight for each individual.As the propensity score serves the function of observed covariates,the propensity score weighting can balance the distribution of the observed covariates between the comparison groups.There are two weighting methods according to the target standard populations:the Inverse probability of treatment weighting(IPTW)and the Standardized mortality ratio weighting(SMRW).Results of the example show that the distribution of the covariates tended to be consistent after weighting,and the IPTW and SMRW methods showed similar effect estimates.Propensity score weighting method can effectively balance the distribution of the confounding factors between the compared groups in non-randomized controlled trials.

Influence of hemoglobin level during early gestation on the development of cognition of preschool children / 中华流行病学杂志

Objective The purpose of this study was to evaluate the effect of hemoglobin (Hb) level during early gestation on the cognitive development of children at 4-6 years of age.Methods A total number of 3609 children were randomly selected from all the live birth infants whose mothers participated in a community intervention trial during 1993-1996 in 13 counties or cities in Jiangsu and Zhejiang provinces. Hb concentration during early gestation was measured at first prenatal examination and intelligence quotients (IQ), including full-scale, verbal and performance were assessed using Chinese-Wechsler Intelligence Scale for Children in 2000-2001 when these children had a mean age of 68 months. Results Compared with children whose mothers were non-anemic during early gestation, children whose mothers were anemic had a 0.6 point higher mean verbal scale IQ, a 0.9 point higher mean performance IQ and a 0.8 point higher mean full-scale IQ.These differences were not statistically significant when children' s gender, age at intelligence test,region, parity and mother' s IQ, education level and occupation were adjusted for. When mother-child pairs were divided into 5 sub-groups of every 20 percentiles according to Hb concentration during early gestation, verbal IQ scores of the lowest(Hb＜ 103 g/L), the moderate(110 g/L≤ Hb＜ 116 g/L)and the highest Hb concentration group (Hb≥124 g/L) were 91.6 ± 18.9, 92.8 ± 18.2 and 90.3 ±18.6, respectively. The performance IQ scores were 104.7 ± 15.2, 1 04.5 ± 14.3 and 103.5 ±15.1, and full-scale IQ scores were 97.8 ± 17.3,98.4 ± 16.3 and 96.4 ± 17.4, respectively. After controlling for confounding factors, children whose mothers had highest Hb concentration were 54% (OR= 1.54,95%CI:1.13-2.11)more likely to have poor verbal scores and 53% (OR= 1.53,95%CI: 1.10-2.12)more likely to have poor full-scale scores than children whose mothers had moderate -Hb concentration. No statistical associations were noticed between high -Hb concentration and performance scores, or between low Hb concentration during early gestation and verbal, performance as well as full-scale score of pre-school children. Conclusion High maternal Hb concentration during early gestation might adversely affect children' s cognitive development.

Study on the current status of spontaneous abortion of primigravid women in Jiaxing of Zhejiang province, China / 中华流行病学杂志

Objective To study the current status of spontaneous abortion of primigravid women in Jiaxing areas of Zhejiang province of China. Methods We analyzed the data from both perinatal healthcare surveillance program and spontaneous abortion, collected in Jiaxing areas by the Institute of Reproductive and Child Health, Peking University. The study population consisted of 14 769 primigravid women (excluding induced abortion, ectopic pregnancy and molar pregnancy as outcomes) attempting to become pregnant who registered between 1993 and 1995. Results 1454 spontaneous abortion cases were identified, with the spontaneous abortion rate as 9.8% (95% CI:9.3%-10.3%). The mean gestational weeks at pregnancy diagnosis were 7.6±2.1 weeks, the mean gestational weeks at miscarriage were (10.1±3.1) weeks and the incidence of first-trimester (≤12 weeks) spontaneous abortion was 7.3%(95%CI: 6.8%-7.7%), accounting for 73.7% of all the spontaneous abortion cases. A peak for risk of miscarriage was around 8-13 weeks, accounting for 37.7% of all spontaneous abortion. The observed multiple Cox regression model showed that increased spontaneous abortion rates were observed in women with age at pregnancy ≥30, being peasants and with higher education level. Conclusion The spontaneous abortion rate of primigravid women in Jiaxing areas was higher than in other areas of China. The maximum occurrence of spontaneous abortions was during period of 8-13 gestation weeks.

Analysis on influencing factors for stunting and underweight among children aged 3-6 years in 15 counties of Jiangsu and Zhejiang provinces / 中华流行病学杂志

Objective To analyze the influencing factors for stunting and underweight among children aged 3-6 years in 15 counties of Jiangsu and Zhejiang provinces so as to provide reference for enhancing growth level among preschool children. Methods Data was from the 183 295 records of Children Follow-up Study Project carried out by the Institute of Reproductive and Child Heath of Peking University and the records of related perinatal health care surveillance system in rural areas of 15 counties/cities of Jiangsu and Zhejiang provinces. WHO-NCHS standard was used to assess the childhood physical level of growth. Data of children's birth and their mothers' perinatal health were correlated to determine influencing factors for childhood stunting and underweight. Results The average stunting rate was 7.95% and underweight rate was 1.55%. Sex, birth weight, preterm birth as well as maternal height, maternal BMI at the first prenatal visit, maternal education and occupation were significantly related to childhood stunting and underweight. Birth weight was the most important influencing factor for childhood underweight. For the groups whose birth weights were ＜2500 g and ≥2500 g, the rates of underweight were 7.77% and 1.46% respectively. Children with low birth weight were at higher risk for underweight (OR=3.68,95% CI: 3.11-4.37). Maternal height was the most important influencing factor for childhood stunting. For the groups whose mothers' heights were ＜155 cm, 155-160 cm, 160-165 cm and ≥165 cm, the stunting rates were 13.01%, 8.76%,6.21% and 4.14% respectively. Compared with the ≥165 cm group, the ＜155 cm group was at higher risk for stunting (OR=3.08, 95% CI: 2.82-3.37). Conclusion Birth weight and maternal height were key factors influencing the growth of children. Perinatal health care and the nutrition starus of pregnant mothers should be improved to promote the growth level of preschool children.

Application of propensity score matching in the design of an epidemiological study / 中华流行病学杂志

In this article, we presented the rationale and calculation procedures of the propcnsity score matching (PSM), and its application in the designing stage of an cpidcrniological study. Based on existing observational data, PSM can be used to select one or more comparable controls for each subject in 'treatment' group according to the propensity scores estimated by 'treatment' variable and main covariates. The results of an example analysis showed that the bias for main confounders between the treated and control samples declined more than 55% after PMS. Conclusion: PSM can reduce most of the confounding bias of the observational study, and can obtain approximate study effect to the randomized controlled trials when used in the designing of thc cpidcmiological study.

The relationship between prepregnancy body mass index and the occurrence of pregnancy induced hypertension / 中华预防医学杂志

<p><b>OBJECTIVE</b>To examine the relationship between prepregnancy body mass index (BMI) and the risk of pregnancy-induced hypertension (PIH) in Chinese population.</p><p><b>METHODS</b>Data were collected in 6 counties/cities covered by Perinatal Health Care Surveillance System which was part of the Sino-American cooperative project on neural tube defects prevention established in 1992. The study population consisted of 83 159 women who attended premarital or preconception medical physical examination and delivered single live births with at least 20 gestational weeks from 1995 to 2000 in Jiaxing area. The Chi-square test was employed to test the difference in the rates of PIH among groups with different BMI. Multivariate logistic regression was conducted to examine the association between prepregnancy BMI and the risk of PIH.</p><p><b>RESULTS</b>The rate of PIH was 11.01% (9153/83 159; 95% CI: 10.79% - 11.22%). The rate of PIH among women with BMI < 18.5 kg/m(2), 18.5 - 22.9 kg/m(2), 23.0 - 24.9 kg/m(2), and > or = 25.0 kg/m(2) were 9.08% (1405/15 472; 95% CI: 8.63% - 9.54%), 10.82% (6389/59 054; 95% CI: 10.57% - 11.07%), 14.63% (943/6444; 95% CI: 13.78% - 15.52%), and 19.00% (416/2189; 95% CI: 17.38% - 20.71%), respectively, the difference was significant (chi(trend)(2) = 261.028, P = 0.000). Taking those with BMI 18.5 - 22.9 kg/m(2) as reference, the unadjusted RR for PIH was 0.82 (95% CI: 0.77 - 0.87) among women with BMI < 18.5 kg/m(2), 1.41 (95% CI: 1.31 - 1.52) among women with BMI 23.0 - 24.9 kg/m(2), and 1.93 (95% CI: 1.73 - 2.16) among women with BMI > or = 25.0 kg/m(2). After controlling for area, maternal age at delivery, educational level, occupation, parity, times of prenatal visit as well as the individual or family history of chronic hypertension, the estimated RR were 0.85 (95% CI: 0.80 - 0.90), 1.37 (95% CI: 1.27 - 1.47) and 1.88 (95% CI: 1.68 - 2.10), respectively.</p><p><b>CONCLUSION</b>High prepregnancy BMI could increase the risk of PIH.</p>

Association between pregnancy-induced hypertension, cesarean delivery and perinatal mortality: a prospective study / 中华流行病学杂志

trimester. Conclusion Moderate and severe PIH early developed during pregnancy could increase the risk of perinatal mortality, while cesarean delivery could decrease the risks in women with PIH.

Maternal passive smoking and the risk of neural tube defects: a case-control study in Shanxi province,China / 中华流行病学杂志

Objective To explore the relationship between maternal passive smoking during early pregnancy and the risk of neural tube defects (NTDs). Methods Data was derived from a populationbased case-control study on birth defects in Shanxi province. The study subjects included 515 NTDs defects cases (236 cases of anencephaly, 237 spina bifida and 42 encephalocele) ascertained during January 2003 and June 2007 in the study areas and 682 normal controls randomly selected in the same residence during the same period as cases. Results The risk of NTDs in their offspring was 1.84 (95 % CI : 1.39-2.44) for mothers with passive smoking history during peri-conceptional period. There was a marked dose-response relation between maternal passive smoking and the risk of NTDs in offspring. Compared to the women without passive smoking, the NTDs risk in offspring was 1.51 for women with occasional passive smoking and 2.44 for women with passive smoking for almost everyday during the peri-conceptional period.Conclusion Maternal passive smoking during peri-conceptional period increased the risk of NTDs in offspring.

Relations between pre-pregnancy body mass index,gestational weight gain,and the occurrence of neonatal asphyxia / 中华流行病学杂志

Objective To assess the relationship between pre-pregnancy body mass index(BMI),weight gain during pregnancy,and the risk of neonatal asphyxia.Methods Data was collected in 6 counties/cities covered by Peri-natal Health Care Surveillance System which was part of a Sino-American cooperative project on neural tube defects prevention established in 1992.The study population consisted of 83 030 women who attended premarital/preconception medical physical examination program and had delivered single live birth with at least 20 gestational weeks from 1995 to 2000 in Jiaxing area,Zhejiang province.Results from the Chi-square test were employed to test the differences in the rates of neonatal asphyxia between groups with different BMI and other characteristics.Multivariate logistic regression method was conducted to examine the association between pre-pregnancy BMI,gestational weight gain,and the risk of asphyxia.Results The average rate of neonatal asphyxia was 11.3%(95% CI:11.1%-11.6%).The rates of neonatal asphyxia among women with BMI＜18.5 kg/m2,18.5-22.9 kg/m2,23.0-24.9 kg/m2,and≥25.0 kg/m2 were 11.0%(95% CI:10.5%-11.5%),11.3%(95% CI:11.1%-11.6%),11.8%(95% CI:11.0%-12.6%),and 12.9%(95% CI:11.6%-14.4%)respectively.The rates of neonatal asphyxia were 12.4% among women with weight gain＜0.3 kg/wk.higher than women with higher weight gain.After adjusting for residencial area,maternal age,educational level,occupation,parity,times of prenatal visit,high-risk experiences during pregnancy,high-risk experiences at time of delivery,gestational week and birth weight,the estimated ORs were 1.03(95% CI:0.97-1.09),1.06(95% CI:0.96-1.16)and 1.14(95% CI:1.00-1.31),respectively.These ORs became 1.02(95% CI:0.95-1.09),1.01(95% CI:0.90-1.13)and 1.08(95% CI:0.92-1.28)after further adjusting the variable "gestational weight gain".The estimated ORs for neonatal asphyxia were 1.06(95% CI:1.01-1.12)for women with weight gain at 0.3-kg/wk and 1.09(95% CI:1.02-1.20)for women with weight gain＜0.3 kg/wk when compared to those with weight gain≥0.5 kg/wk.Conclusion Lower weight gain seemed to have the effect of increasing the risk of neonatal asphyxia.