Determinants of zinc intake in low-income black and white pregnant women.

A prospective study was conducted to evaluate and compare the determinants of dietary zinc intake in black and white low-income pregnant women. The study population consisted of 1298 low-income women (70% Black, 30% White) who received prenatal care at University Hospital at the University of Alabama in Birmingham from 1985 to 1989. Various maternal characteristics were evaluated at the first prenatal visit. Two 24 h recalls were obtained at 18 and 30 wk of gestation to calculate the intakes of dietary zinc and other nutrients. Student's t test, chi2, Pearson correlation coefficients, and multiple regression analyses were used to compare and evaluate the determinants of zinc and other nutrient intakes in Black and White subjects. The mean prepregnancy body mass index and the mean intake of zinc, energy, and all the other nutrients except calcium were significantly higher in Black than in White subjects. There was a significant correlation between zinc and energy intake (r = 0.69, p = 0.001). Age, marital status, parity, socioeconomic status, smoking, and alcohol intake were not significant predictors of zinc or other nutrient intakes. After adjusting for energy intake, race was the only significant predictor of dietary zinc intake. Race and energy intake explained 24% of the variation in zinc intake. Results of this study indicate that after adjusting for other covariates, race and energy intakes are the only predictors of zinc intake in low-income pregnant women.

The preterm prediction study: the value of new vs standard risk factors in predicting early and all spontaneous preterm births. NICHD MFMU Network.

OBJECTIVES: This study was undertaken to determine the relationship between fetal fibronectin, short cervix, bacterial vaginosis, other traditional risk factors, and spontaneous preterm birth. METHODS: From 1992 through 1994, 2929 women were screened at the gestational age 22 to 24 weeks. RESULTS: The odds ratios for spontaneous preterm birth were highest for fetal fibronectin, followed by a short cervix and history of preterm birth. These factors, as well as bacterial vaginosis, were more strongly associated with early than with late spontaneous preterm birth. Bacterial vaginosis was more common--and a stronger predictor of spontaneous preterm birth--in Black women, while body mass index less than 19.8 was a stronger predictor in non-Black women. This analysis suggests a pathway leading from Black race through bacterial vaginosis and fetal fibronectin to spontaneous preterm birth. Prior preterm birth is associated with spontaneous preterm birth through a short cervix. CONCLUSIONS: Fetal fibronectin and a short cervix are stronger predictors of spontaneous preterm birth than traditional risk factors. Bacterial vaginosis was found more often in Black than in non-Black women and accounted for 40% of the attributable risk for spontaneous preterm birth at less than 32 weeks.

Plasma and erythrocyte zinc concentrations and their relationship to dietary zinc intake and zinc supplementation during pregnancy in low-income African-American women.

OBJECTIVE: To evaluate the effects of usual dietary intake of zinc and of zinc supplementation during pregnancy on plasma and erythrocyte zinc concentrations. DESIGN: A randomized, double-blind, placebo-controlled trial. SUBJECTS: Low-income African-American women (n = 580) assigned randomly to groups at 19 weeks of gestation. INTERVENTION: A daily dose of zinc (25 mg) or a placebo until delivery. MAIN OUTCOME MEASURES: Plasma, erythrocyte, and dietary zinc levels. STATISTICAL ANALYSES: Multiple regression and repeated measures analysis of variance. RESULTS: In both the placebo and the supplemented groups, when all subjects were grouped by usual dietary zinc intake above or below the median (12 mg/day), results were the same: Women with high dietary zinc intake had higher erythrocyte zinc levels at the time of randomization and at all subsequent measurements during pregnancy than those who had low dietary zinc intake (P < or = .06; difference not significant for zinc-supplemented group); no difference was observed for plasma zinc levels. On the other hand, when the subjects were stratified at the median by total daily zinc intake (usual dietary zinc + 25 mg zinc supplement) during pregnancy, a significant difference in plasma zinc levels (P < .005) was found between women with high total zinc intake (mean = 38 mg/day) and low total intake (mean = 13 mg/day) at 26, 32, and 38 weeks of gestation; however, no such differences were found in erythrocyte zinc levels. APPLICATIONS: These results should help dietitians and other health professionals better understand the expected changes in plasma and erythrocyte zinc levels during pregnancy, and the relationship between dietary and supplemental zinc and zinc nutriture.

Plasma alkaline phosphatase and pregnancy outcome.

The objective was to determine the relationship between plasma alkaline phosphatase (AP) activity and birthweight (BWT) and preterm delivery (PTD). Five hundred eighty African-American women had plasma AP activities measured at various gestational ages (GA) with the results compared to a number of pregnancy outcomes. Plasma AP activity rose linearly during pregnancy from a mean of 39 U/L at 19 weeks to 130 U/L at delivery. In individual women, AP activities were consistently high or low as confirmed by correlation coefficients in adjacent time periods ranging from 0.63 to 0.87. AP at 19 weeks was not significantly associated with any outcome measure. However, at 26 weeks, AP in the highest quartile was associated with a 15.0% incidence of PTD < 37 weeks compared to 6.8% in the lower three quartiles (P = .004). For PTD < or = 32 weeks, the difference of PTD was 6.8 vs. 1.6% (P < .003). When women in the highest quartile of increase in AP from 19 to 26 weeks were compared to those in the lower quartiles, the rate of PTD < 37 weeks was 15.2 vs. 6.4% (P = .002), and the rate of PTD < or = 32 weeks was 6.1 vs. 1.7%, (P = .01). The mean BWT for the highest vs. the lower three quartiles in rate of increase was 3,058 vs. 3,288 g (P = .0005) and the mean GA was 38.1 vs. 39.2 weeks (P = .0001). Regression analyses adjusting for multiple confounders confirmed the association between high AP at 26 weeks and PTD < 37 weeks [OR (95% C.I.), 2.4 (1.2-4.8)] and PTD < or = 32 weeks [OR (95% C.I.), 3.7 (1.2-11.7)]. Similar results were found among women with a large increase in AP between 19 and 26 weeks. From these results we conclude that high or increasing AP activity at 26 weeks, but not 19 weeks, was significantly associated with subsequent PTD and a lower BWT.

The relationship between maternal characteristics and fetal and neonatal anthropometric measurements in women delivering at term: a summary.

BACKGROUND: We wanted to determine the relationship between a number of maternal characteristics and various fetal and neonatal anthropometric measurements determined by ultrasound and at birth. METHODS: A total of 1205 term singleton maternal-infant pairs were studied. Various ultrasound measurements obtained at 18, 24, 30 and 36 weeks' gestation and neonatal anthropometric measurements obtained at birth were studied in relationship to various maternal characteristics using univariate and multivariate techniques. RESULTS: Black race, female sex, cigarette smoking, drug use, having a previous low birthweight infant, maternal hypertension and being short or thin or failing to gain weight each resulted in a birthweight decrease of 100 to 300 g. The effect of each of these characteristics on each ultrasound measurement, the timing of the effect, and its ultimate effect on neonatal anthropometric measurements are described. CONCLUSION: The data presented in this paper provide a more complete understanding of the relationship between maternal characteristics, infant sex, and various fetal ultrasound and neonatal measurements.

The preterm prediction study: maternal stress is associated with spontaneous preterm birth at less than thirty-five weeks' gestation. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

OBJECTIVE: Our purpose was to determine whether various measures of poor psychosocial status in pregnancy are associated with spontaneous preterm birth, fetal growth restriction, or low birth weight. STUDY DESIGN: Anxiety, stress, self-esteem, mastery, and depression were assessed at 25 to 29 weeks in 2593 gravid women by use of a 28-item Likert scale. Scores for each psychosocial subscale were determined, and an overall psychosocial score was calculated. Scores were divided into quartiles, and the lowest quartile scores were used to define poor psychosocial status. The percent spontaneous preterm birth, low birth weight, and fetal growth restriction in women with low and high psychosocial scores were compared. Logistic regression analyses provided the odds ratios and 95% confidence intervals. RESULTS: Analyses revealed that stress was significantly associated with spontaneous preterm birth and with low birth weight with odds ratios of 1.16, p = 0.003, and 1.08, p = 0.02, respectively, for each point on the scale. A low score on the combined scale or on any subscale other than stress did not predict spontaneous preterm birth, fetal growth restriction, or low birth weight. After multivariate adjustment was performed for psychosocial status, substance use, and demographic traits, black race was the only variable significantly associated with spontaneous preterm birth, fetal growth restriction, and low birth weight; stress and low education were associated with spontaneous preterm birth and low birth weight. CONCLUSION: Stress was associated with spontaneous preterm birth and low birth weight even after adjustment for maternal demographic and behavioral characteristics. Black race continues to be a significant predictor of spontaneous preterm birth, fetal growth restriction, and low birth weight even after adjustment for stress, substance use, and other demographic factors.

Plasma ferritin and pregnancy outcome.

OBJECTIVE: Plasma ferritin is considered the best measure of total body iron, with low levels diagnostic of iron deficiency. High levels have been associated with inflammation and infection. We determined the relationship between plasma ferritin, birth weight, and preterm delivery. STUDY DESIGN: Plasma ferritin and hematocrit values were measured at 19, 26, and 36 weeks' gestational age and correlated with birth weight and preterm delivery (< or = 32 and < 37 weeks) in 580 indigent black women. RESULTS: Hematocrit levels measured at any gestational age did not correlate significantly with birth weight or preterm delivery. Regardless of the gestational age of sampling, ferritin levels in the lowest quartile did not correlate significantly with subsequent preterm delivery. However, at 26 weeks, compared with the three lower quartiles, ferritin levels in the highest quartile were significantly associated with preterm delivery < or = 32 weeks, 6.5% versus 2.3% (p = 0.02), with preterm delivery < 37 weeks, 14% versus 8% (p = 0.04), and with birth weight < 1500 gm, 6.5% versus 2.0% (p = 0.01). Plasma ferritin levels in the highest quartile at 19, 26, and 36 weeks were associated with birth weight < or = 2500 gm, 14% versus 8% (p = 0.03), 12% versus 7% (p = 0.05), and 10% versus 2% (p = 0.0001), respectively, compared with the lower quartiles. Ferritin levels in the highest quartile were always associated with a lower mean birth weight than were those in the lower three quartiles: 19 weeks, 2999 gm versus 3225 gm, (p = 0.002); 26 weeks, 3065 gm versus 3257 gm, (p = 0.005); and 36 weeks, 3182 gm versus 3323 gm, (p = 0.009). Regression analyses controlling for multiple potential confounders confirmed that at 26 weeks ferritin levels in the highest quartile had an odds ratio and 95% confidence interval for preterm birth < 37 weeks of 2.0 (1.1 to 3.8), preterm delivery < or = 32 weeks of 2.7 (0.99 to 7.6), birth weight < or = 1500 gm of 3.9 (1.2 to 12.2), and birth weight < or = 2500 gm of 2.0 (1.0 to 4.0) compared with the three lower ferritin quartiles. CONCLUSION: High, but not low, plasma ferritin levels, especially at 26 weeks, were strongly associated with subsequent preterm delivery and birth weight.

Factors influencing plasma zinc levels in low-income pregnant women.

Plasma zinc (Zn) concentrations were measured in 4376 indigent women (86% African-American), at at mean (+/- SD) gestational age of 15 (+/- 7.8) wk to determine the relationship between various maternal characteristics and plasma Zn levels during pregnancy. Mean Plasma An levels were lower in African-American women than in Caucasian women, in multiparous women than in primiparous women, and in women with body weight > 69.9 kg than in those with body weight < or = 69.9 kg (p < or = 0.001 for each comparison). There were no significant differences related to maternal age, marital status, education, or smoking habit. Multiple regression analysis, including maternal prepregnancy weight, race, age, parity, smoking habit, education, and marital status indicated that race, parity, and pregnancy weight were significantly associated with maternal plasma Zn levels, adjusted for gestational age. Maternal race was the best predictor of plasma Zn concentrations among the population of pregnant women studied A significant proportion of variance in maternal plasma Zn levels. remained unexplained after taking into account various maternal characteristics. The reasons for lower plasma Zn levels in African-American women, compared to Caucasian women, during pregnancy are unknown.

The preterm prediction study: a clinical risk assessment system.

OBJECTIVE: Our aims were to develop a risk assessment system for the prediction of spontaneous preterm delivery using clinical information available at 23 to 24 weeks' gestation and to determine the predictive value of such a system. STUDY DESIGN: A total of 2929 women were evaluated between 23 and 24 weeks' gestation at 10 centers. Demographic factors, socioeconomic status, home and work environment, drug and alcohol use, and medical history were evaluated. Information regarding symptoms, cultures, and treatments in the current pregnancy were ascertained. Anthropomorphic and cervical examinations were performed. Univariate analysis and multivariate logistic regression were performed in a random selection, constituting 85% of the study population. The derived risk assessment system was applied to the remaining 15% of the population to evaluate its validity. RESULTS: A total of 10.4% of women were delivered of preterm infants. The multivariate models for spontaneous preterm delivery were highly associated with spontaneous preterm delivery (p < 0.0001). A low body mass index (<19.8) and increasing Bishop scores were significantly associated with spontaneous preterm delivery in nulliparous and multiparous women. Black race, poor social environment, and work during pregnancy were associated with increased risk for nulliparous women. Prior obstetric outcome overshadowed socioeconomic risk factors in multiparous women with a twofold increase in the odds of spontaneous preterm delivery for each prior spontaneous preterm delivery. Current pregnancy symptoms, including vaginal bleeding, symptomatic contractions within 2 weeks, and acute or chronic lung disease were variably associated with spontaneous preterm delivery in nulliparous and multiparous women. When the system was applied to the remainder of the population, women defined to be at high risk for spontaneous preterm delivery (> or = 20% risk) carried a 3.8-fold (nulliparous women) and 3.3-fold (multiparous women) higher risk of spontaneous preterm delivery than those predicted to be at low risk. However, the risk assessment system identified a minority of women who had spontaneous preterm deliveries. The sensitivities were 24.2% and 18.2% and positive predictive values were 28.6% and 33.3%, respectively, for nulliparous and multiparous women. CONCLUSIONS: Although it is possible to develop a graded risk assessment system that includes factors that are highly associated with spontaneous preterm delivery in nulliparous and multiparous women, such a system does not identify most women who subsequently have a spontaneous preterm delivery. This system has investigational value as the basis for evaluating new technologies designed to identify at-risk subpopulations.

The preterm prediction study: fetal fibronectin testing and spontaneous preterm birth. NICHD Maternal Fetal Medicine Units Network.

OBJECTIVE: To evaluate the presence of fetal fibronectin in the cervix and vagina as a screening test for spontaneous preterm birth. METHODS: Two thousand nine hundred twenty-nine women at ten centers were routinely screened every 2 weeks from 22-24 to 30 weeks for cervical and vaginal fetal fibronectin. A positive test was defined as a value equal to or greater than 50 ng/mL. The relation between a positive test at four gestational ages and spontaneous preterm birth at various intervals after the test was determined. RESULTS: In each testing period, 3-4% of the fetal fibronectin tests were positive. The correlation between cervical and vaginal fetal fibronectin at the same visit was always approximately 0.7 (P < .001), and that between cervical or vaginal fetal fibronectin in consecutive visits was between 0.17 and 0.25 (P < .001). The sensitivity of fetal fibronectin at 22-24 weeks to predict spontaneous preterm birth at less than 28 weeks was 0.63, and the relative risk for a positive versus negative test was 59. The specificity was always 96-98%, whereas the positive predictive value rose from 13% to 36% as the upper limit of the definition of preterm birth was increased from less than 28 to less than 37 weeks. The relative risk for spontaneous preterm birth after a positive fetal fibronectin test compared with a negative fetal fibronectin test varied substantially by testing period and by the definition of spontaneous preterm birth, but always remained greater than 4 and statistically significant. CONCLUSION: A positive cervical or vaginal fetal fibronectin test at 22-24 weeks predicted more than half of the spontaneous preterm births at less than 28 weeks (sensitivity 0.63). As the definition of spontaneous preterm birth was extended to include later gestational ages or when the fetal fibronectin test was performed later in pregnancy, the level of association between a positive fetal fibronectin test and spontaneous preterm birth, while remaining highly significant, tended to decrease. Although fetal fibronectin is an excellent test for predicting spontaneous preterm birth, we present no evidence that the use of this test will result in a reduction in spontaneous preterm birth.

The length of the cervix and the risk of spontaneous premature delivery. National Institute of Child Health and Human Development Maternal Fetal Medicine Unit Network.

BACKGROUND: The role of the cervix in the pathogenesis of premature delivery is controversial. In a prospective, multicenter study of pregnant women, we used vaginal ultrasonography to measure the length of the cervix; we also documented the incidence of spontaneous delivery before 35 weeks' gestation. METHODS: At 10 university-affiliated prenatal clinics, we performed vaginal ultrasonography at approximately 24 and 28 weeks of gestation in women with singleton pregnancies. We then assessed the relation between the length of the cervix and the risk of spontaneous preterm delivery. RESULTS: We examined 2915 women at approximately 24 weeks of gestation and 2531 of these women again at approximately 28 weeks. Spontaneous preterm delivery (at less than 35 weeks) occurred in 126 of the women (4.3 percent) examined at 24 weeks. The length of the cervix was normally distributed at 24 and 28 weeks (mean [+/- SD], 35.2 +/- 8.3 mm and 33.7 +/- 8.5 mm, respectively). The relative risk of preterm delivery increased as the length of the cervix decreased. When women with shorter cervixes at 24 weeks were compared with women with values above the 75th percentile, the relative risks of preterm delivery among the women with shorter cervixes were as follows: 1.98 for cervical lengths at or below the 75th percentile (40 mm), 2.35 for lengths at or below the 50th percentile (35 mm), 3.79 for lengths at or below the 25th percentile (30 mm), 6.19 for lengths at or below the 10th percentile (26 mm), 9.49 for lengths at or below the 5th percentile (22 mm), and 13.99 for lengths at or below the 1st percentile (13 mm) (P < 0.001 for values at or below the 50th percentile; P = 0.008 for values at or below the 75th percentile). For the lengths measured at 28 weeks, the corresponding relative risks were 2.80, 3.52, 5.39, 9.57, 13.88, and 24.94 (P < 0.001 for values at or below the 50th percentile; P = 0.003 for values at the 75th percentile). CONCLUSIONS: The risk of spontaneous preterm delivery is increased in women who are found to have a short cervix by vaginal ultrasonography during pregnancy.

Reduced incidence of preterm delivery with metronidazole and erythromycin in women with bacterial vaginosis.

BACKGROUND: Pregnant women with bacterial vaginosis may be at increased risk for preterm delivery. We investigated whether treatment with metronidazole and erythromycin during the second trimester would lower the incidence of delivery before 37 weeks' gestation. METHODS: In 624 pregnant women at risk for delivering prematurely, vaginal and cervical cultures and other laboratory tests for bacterial vaginosis were performed at a mean of 22.9 weeks' gestation. We then performed a 2:1 double-blind randomization to treatment with metronidazole and erythromycin (433 women) or placebo (191 women). After treatment, the vaginal and cervical tests were repeated and a second course of treatment was given to women who had bacterial vaginosis at that time (a mean of 27.6 weeks' gestation). RESULTS: A total of 178 women (29 percent) delivered infants at less than 37 weeks' gestation. Eight women were lost to follow-up. In the remaining population, 110 of the 426 women assigned to metronidazole and erythromycin (26 percent) delivered prematurely, as compared with 68 of the 190 assigned to placebo (36 percent, P = 0.01). However, the association between the study treatment and lower rates of prematurity was observed only among the 258 women who had bacterial vaginosis (rate of preterm delivery, 31 percent with treatment vs. 49 percent with placebo; P = 0.006). Of the 358 women who did not have bacterial vaginosis when initially examined, 22 percent of those assigned to metronidazole and erythromycin and 25 percent of those assigned to placebo delivered prematurely (P = 0.55). The lower rate of preterm delivery among the women with bacterial vaginosis who were assigned to the study treatment was observed both in women at risk because of previous preterm delivery (preterm delivery in the treatment group, 39 percent; and in the placebo group, 57 percent; P = 0.02) and in women who weighed less than 50 kg before pregnancy (preterm delivery in the treatment group, 14 percent; and in the placebo group, 33 percent; P = 0.04). CONCLUSIONS: Treatment with metronidazole and erythromycin reduced rates of premature delivery in women with bacterial vaginosis and an increased risk for preterm delivery.

The effect of zinc supplementation on pregnancy outcome.

OBJECTIVE: To evaluate whether zinc supplementation during pregnancy is associated with an increase in birth weight. DESIGN: A randomized double-blind placebo-controlled trial. SETTING: Outpatient clinic and delivery service at the University of Alabama at Birmingham. PATIENTS: Five hundred eighty medically indigent but otherwise healthy African-American pregnant women with plasma zinc levels below the median at enrollment in prenatal care, randomized at 19 weeks' gestational age. Women were subdivided by the population median body mass index of 26 kg/m2 into two groups for additional analyses. INTERVENTION: Women who were taking a non-zinc-containing prenatal multivitamin/mineral tablet were randomized to receive either a daily dose of 25 mg of zinc or a placebo until delivery. MAIN OUTCOME MEASURES: Birth weight, gestational age at birth, and head circumference at birth. RESULTS: In all women, infants in the zinc supplement group had a significantly greater birth weight (126 g, P = .03) and head circumference (0.4 cm, P = .02) than infants in the placebo group. In women with a body mass index less than 26 kg/m2, zinc supplementation was associated with a 248-g higher infant birth weight (P = .005) and a 0.7-cm larger infant head circumference (P = .007). Plasma zinc concentrations were significantly higher in the zinc supplement group. CONCLUSIONS: Daily zinc supplementation in women with relatively low plasma zinc concentrations in early pregnancy is associated with greater infant birth weights and head circumferences, with the effect occurring predominantly in women with a body mass index less than 26 kg/m2.

Maternal serum thromboxane B2 reduction versus pregnancy outcome in a low-dose aspirin trial.

OBJECTIVE: Our purpose was to determine whether in a low-dose aspirin trial a longitudinal decrease in maternal serum thromboxane B2 is associated with improvement in pregnancy outcomes. STUDY DESIGN: A total of 606 healthy nulliparous women with singleton gestations were randomized at 24 weeks to either 60 mg of aspirin or a placebo. Maternal serum thromboxane B2 was measured at randomization, at 29 to 31 weeks, at 34 to 36 weeks, and at delivery. After delivery, and without knowledge of patient outcome or group assignment, patients were categorized as having had either a longitudinal twofold or greater (> or = 50%) or less than twofold reduction (< 50%) in thromboxane B2 from baseline levels at randomization. RESULTS: Of 606 entrants, 92% had sufficient thromboxane B2 determinations to allow categorization. Whether patients were assigned to aspirin or placebo, birth weight was significantly greater in women who had a twofold or greater reduction in maternal serum thromboxane B2 levels. When the aspirin and placebo groups were combined, women with a twofold or greater reduction in thromboxane B2 levels had less preeclampsia, 1.9% (6/314) versus 5.7% (14/244) (p = 0.016), less preterm delivery (5.7% vs 10.7%, p = 0.032), fewer small-for-gestational-age newborns, 9 of 314 (2.95) versus 17 of 244 (7%) (p = 0.023), and a higher mean birth weight, 3314 gm versus 3121 gm (p = 0.0001). CONCLUSION: Women with a twofold or greater longitudinal reduction in maternal serum thromboxane B2 had less preeclampsia and prematurity, fewer small-for-gestational-age newborns, and higher birth weights than women with less than a twofold reduction.

The origin and outcome of preterm twin pregnancies.

OBJECTIVE: To define the etiology of preterm twin births and determine the contribution of twin births to preterm birth and related morbidity and mortality. METHODS: The March of Dimes Multicenter Prematurity and Prevention Study included a total of 33,873 women who delivered between 1982-1986, 432 (1.3%) of which delivered twins. Women were classified by reason for preterm birth and ethnicity. Neonates were classified as to stillbirth, neonatal death, and various short-term morbidities. A second data set from one center consisted of infants who weighed 1000 g or less, were born between 1979-1991, and survived to 1 year of age (n = 386, 15% twins); this was used to determine if twins and singletons born at comparable gestational ages have a similar risk for major developmental handicaps. RESULTS: Of the deliveries in the data set, 54% of twins were preterm compared with 9.6% among singletons. Of those born preterm, twins were born at a significantly earlier gestational age than were singletons. Only 2.6% of all neonates born were twins, but they represented 12.2% of all preterm infants, 15.4% of all neonatal deaths, and 9.5% of all fetal deaths. Spontaneous labor accounted for 54% of twin births, premature rupture of membranes accounted for 22%, and indicated deliveries accounted for 23%. Of the indicated preterm births in twins, 44% were due to maternal hypertension, 33% to fetal distress or fetal growth restriction, 9% to placental abruption, and 7% to fetal death. Comparing infants of similar gestational age, twins weighed less, but had a mortality equivalent to that of singletons after 29 weeks. Between 26-28 weeks' gestation, the risk of mortality for twins versus singletons was 1.6 (95% confidence interval 1.1-2.5). Preterm twins did not have significantly more respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, or other short-term morbidity than did preterm singletons. Twins who weighed 500-1000 g and survived to 1 year had a 25% rate of major developmental handicaps. However, when gestational age was controlled, the rate of major handicaps was not higher in twins than in singletons. CONCLUSIONS: Twins accounted for a disproportional amount of preterm birth and associated morbidity and mortality. Also, when preterm twins were compared with preterm singletons and corrected for their gestational ages, the rates of morbidity were similar. Preterm twins weighing less than 1000 g did not have an increased prevalence of major handicaps at 1 year of age compared with preterm singletons.

The relationship of maternal attitude toward weight gain to weight gain during pregnancy and low birth weight.

OBJECTIVE: To evaluate the relationships between maternal attitude toward weight gain, actual weight gain, and infant birth weight. METHODS: Maternal attitude toward weight gain during pregnancy was assessed in 1000 women, using an 18-item questionnaire administered at a mean of 20 weeks' gestation. Composite scores were compared with pregnancy weight gain, maternal body mass index (BMI), and infant birth weight. RESULTS: In the total population, the attitude score was not significantly related to pregnancy weight gain (r = -0.05, P = .08) and was negatively associated with birth weight (r = -0.09, P < .004). Maternal body size as measured by BMI was strongly associated with both weight gain and birth weight. Obese women (BMI greater than 26.6) tended to have negative attitudes and had the lowest mean weight gain (10.2 kg), but had the heaviest babies (3400 g). Thin women (BMI less than 19.6) had significantly higher attitude scores and a higher mean weight gain (14.1 kg) than did obese women. A significantly larger proportion of thin women achieved recommended gains when compared with larger women, but had the lightest babies (3114 g). Within the group of thin women, after adjustment for smoking, race, and gestational age at delivery, attitude scores were not significantly associated with either weight gain or birth weight. CONCLUSION: Maternal attitude regarding weight gain is strongly influenced by pre-pregnancy body size; thin women tend to have positive attitudes and obese women tend to have negative attitudes about weight gain. Within BMI groups, a positive attitude does not predict appropriate weight gain or birth weight. These findings may explain in part why nutritional counseling programs tend to be associated with only minimal increases in birth weight.

Cervical examination and tocodynamometry at 28 weeks' gestation: prediction of spontaneous preterm birth.

OBJECTIVE: We determined the value of cervical examination and tocodynamometry in identifying nulliparous women at risk for spontaneous preterm delivery. STUDY DESIGN: At 27.5 +/- 0.8 weeks' gestation 589 women underwent 30 minutes of tocodynamometry, and 570 of these had a cervical examination. Positive findings on these examinations were compared to the rate of spontaneous preterm delivery, defined as those deliveries following the onset of spontaneous labor or premature rupture of membranes. RESULTS: The two best predictors of spontaneous preterm birth were two or more contractions in 30 minutes and the presence of a soft or medium consistency on cervical examination. As the contractions increased from zero to four or more, the rate of spontaneous preterm delivery rose from 4.2% to 18.2%. CONCLUSION: In nulliparous women at 28 weeks' gestation, uterine contractions and several components of the cervical examination predicted spontaneous preterm birth.

Risk factors for fetal death in white, black, and Hispanic women. Collaborative Group on Preterm Birth Prevention.

OBJECTIVE: To document the relation between stillbirth and various demographic, obstetric, and medical risk factors. METHODS: We analyzed the risk factors and medical origins of 403 stillbirths. The population studied included 34,350 births occurring during the March of Dimes Preterm Birth Prevention Trial. All births occurring in five perinatal centers from 1982-1986 were included in the analysis. Stillbirth was defined as those infants born at 20 weeks' gestation or later whose Apgar score was 0 at 1 and 5 minutes. RESULTS: Stillbirth occurred in 1.2% of all births. Fifty-one percent occurred before 28 weeks and only 18% were at term. Blacks had a greater risk of stillbirth when compared to other women. Prior preterm delivery yielded nearly a two-fold increase in the risk of stillbirth. Preeclampsia, chronic hypertension, and class A or class B-R diabetes were not associated with an increased risk of stillbirth. Other medical factors (hemoglobinopathies, Rh sensitization) resulted in a greater than sixfold increase in the rate of stillbirth, and congenital anomalies resulted in a fivefold increase. Abruption was associated with a 12-fold increase in the risk of stillbirth; nearly 14% of all stillbirths were associated with abruption. CONCLUSION: Eighty-two percent of all stillbirths occurred before term, and more than 50% occurred before 28 weeks. The majority of stillbirths were not explained by medical complications, but instead were often associated with other risk factors related to preterm birth. Further investigations are needed to understand the complex etiology of stillbirth.

The relationship between maternal skinfold thickness, smoking and birthweight in black and white women.

A prospective study was conducted in a sample of 1491 multiparous women to ascertain whether the relationship between maternal tricep skinfold thickness and infant birthweight is modified by smoking status and whether the relationship is different in white and black infants. Maternal tricep skinfold thickness measured at midpregnancy was a significant predictor of infant birthweight in both white and black infants after adjusting for gestational age at birth, maternal height, maternal age, parity, alcohol consumption and sex of the infant. However, maternal tricep skinfold thickness was a better predictor of birthweight in smokers compared with nonsmokers. Both white and black women with tricep skinfold thickness below the sample mean had lower infant birthweight than women with tricep skinfold at or above the mean, after adjusting for gestational age at birth, but the difference was greater in smokers (198 g for white and 221 g for black infants) than in nonsmokers (124 g for white and 221 g for black infants) than in nonsmokers maternal subcutaneous fat measured by tricep skinfold thickness has a greater effect on infant birthweight in smokers compared with nonsmokers, with similar effects in white and black infants.

The predictive value of umbilical artery Doppler studies for preeclampsia or fetal growth retardation in a preeclampsia prevention trial.

OBJECTIVE: To determine the clinical utility of longitudinal Doppler umbilical artery systolic-diastolic ratios (S/D) to predict the occurrence of either preeclampsia or fetal growth retardation (FGR) in a low-risk population. METHODS: Healthy nulliparas with singleton gestations were enrolled in a double-blind trial of low-dose (60 mg) aspirin for preeclampsia prevention. Treatment was initiated at 24 weeks and continued until delivery. Continuous-wave Doppler studies were scheduled before assignment to treatment and at 27-31, 32-36, and 37-42 weeks. Preeclampsia was defined as a persistent diastolic blood pressure of at least 90 mmHg with proteinuria, and FGR was defined as birth weight below the tenth percentile. Doppler values were considered abnormal if they exceeded the 90th percentile for the gestational age range in the study population. Summary predictive values were computed for the abnormal S/D at each gestational age interval. To assess the potential effect of the administration of low-dose aspirin, logistic regression was used to model the relation between the Doppler indices, aspirin use, and these abnormal pregnancy outcomes. RESULTS: A total of 1665 Doppler examinations were performed on 565 women. Forty-four fetuses developed FGR and 21 women were diagnosed with preeclampsia. The positive predictive values of an abnormal S/D for the subsequent development of FGR were 13-17% across the gestational age ranges studied, and the positive predictive values for preeclampsia were 0-5%. Aspirin treatment did not affect the relation between the Doppler indices and these outcomes in the logistic regression model. CONCLUSION: Elevated umbilical artery S/D is not a clinically useful predictor of either FGR or preeclampsia in a low-risk population.