An investigation of social and class differences in very-low birth weight outcomes: a continuing public health concern.

The objective of this study was to examine the relationship of nonmedical factors, including socioeconomic status, social class, education, race, and social support, to low birth weight. In a case-control study of all resident very-low-birth-weight births between December 1, 1989, and March 31, 1991, mothers completed an extensive survey related to their experience of pregnancy, including prenatal and postnatal care. Cases were defined as very-low-birth-weight (VLBW) infants and were matched to moderately-low-birth-weight and normal-birth-weight infants in race, age, and maternal residence. The hypothesis that social and class factors are more predictive of low birth weight than medical factors alone for women without chronic health problems was supported. Although the degree of the association varies depending on birth weight outcome, race even though addressed through matching--continued to play an important role in birth outcomes. A comparison of logistic model performance with and without the inclusion of social factors indicated the importance these variables play in prediction of birth outcomes. This is one of the few studies undertaken that explicitly investigates impact of patient factors on medical care.

Changing patterns in regionalization of perinatal care and the impact on neonatal mortality.

OBJECTIVE: Our goal was to study changing patterns of low-birth-weight outcome over the past decade as deregionalized perinatal care has occurred. STUDY DESIGN: Live births and neonatal mortality for two 5-year periods (1982 to 1986 vs 1990 to 1994) were calculated by hospital of delivery in the state of Missouri. Self-designated level of perinatal care was contrasted with number of deliveries and nursery census to evaluate outcome. Regression models were constructed to compare outcome between levels of care. RESULTS: There has been a significant shift of deliveries into self-designated level II and III perinatal centers. However, this is largely a result of redesignation of care rather than an actual increase in acuity or census. The relative risk of neonatal mortality for very-low-birth-weight infants is 2.28 in level II centers compared with level III centers, and is unchanged (2.57) from 10 years earlier. Nearly 14% of very-low-birth-weight deliveries still occur at non-level III centers. CONCLUSION: Changing patterns of perinatal regionalization have not improved outcome for inborn infants < 1500 gm except in level III centers. Attempts should be made to deliver very-low-birth-weight infants in level III centers.

Relation between very low birth weight and developmental delay among preschool children without disabilities.

The authors examined the relation between very low birth weight (VLBW: < 1,500 g) and possible developmental delay (DELAY) in the absence of frank developmental disability among young children. The prevalence of DELAY in a population-based cohort (Missouri resident births born from December 1989 through March 1991) of singleton VLBW children (n = 367) was compared with the prevalence of DELAY among both moderately low birth weight (MLBW: 1,500-2,499 g; n = 553) and normal birth weight (NBW: > or = 2,500 g; n = 555) singleton control children. DELAY was defined by nine measures of performance on the Denver Developmental Screening Test II at a median adjusted age of 15 months (range: 9-34 months). Subjects were asymptomatic for disabling conditions at developmental follow-up. Apparently well VLBW children were consistently at greater risk for both moderate and severe measures of DELAY and for DELAY across four functional areas than were either the MLBW (adjusted odds ratios: 1.4-2.7) or NBW children (adjusted odds ratios: 2.1-6.3). The greatest prevalence of DELAY tended to be among appropriate-for-gestational age VLBW children who were also the most premature. This study supports developmental follow-up of nondisabled VLBW children because of the significantly elevated risk for DELAY among apparently normal infants.

Pregnancy wantedness and adverse pregnancy outcomes: differences by race and Medicaid status.

The relationship between pregnancy wantedness and adverse pregnancy outcomes was studied using data from 2,828 mothers who participated in the Missouri Maternal and Infant Health Survey. The wantedness of a pregnancy was measured using traditional classifications of mistimed and unwanted, as well as additional measures gauging how the woman felt about the pregnancy while she was pregnant. Fifty-eight percent of the very low birth weight infants and 59% of the moderately low birth weight infants resulted from unintended pregnancies, as did 62% of the normal-birth-weight infants. Logistic regression showed that mothers of very low birth weight infants were significantly more likely than those who had a normal-weight baby to report that they had felt unhappy about the pregnancy (odds ratio of 1.53). Very low birth weight was also associated with early denial of the pregnancy (1.54). Odds ratios associating these two unwantedness categories with low-birth-weight babies were higher among Medicaid recipients than among women not receiving Medicaid. Associations between very low birth weight and the denial variable were also significant among white women when very low birth weight outcomes were compared with normal outcomes, but there was no significant association among black women. There were no significant associations between low birth weight and the traditional unwantedness variables.

PIP: This study examines the relationship between pregnancy wantedness and adverse pregnancy outcomes among 2828 mothers who participated in the Missouri Maternal and Infant Health Survey. The survey was designed as a population-based case-control study of very low birth weight infants born to Missouri residents during December 1, 1989, and March 31, 1991. Infants of moderate and normal birth weight were the controls. Stillbirths were included, but multiple pregnancies were excluded. 36% of the sample were in-patients, 38% were Black, 62% were White, 23% were teenagers, 54% were in their 20s, 52% were married, and 52% lived in a major metropolitan area. 45% of mothers qualified for Medicaid. 779 women gave birth to a low birth weight infant, 799 gave birth to a moderately low birth weight infant, and 800 gave birth to a normal birth weight infant. 450 infants were stillbirths. Pregnancy wantedness was defined by traditional measures of mistimed and unwanted pregnancies as used in the NSFG and some newer measures, such as feelings about being pregnant. Six measures were used: unintended (mistimed and unwanted), mistimed, unwanted, unhappy about the pregnancy, unsure about the pregnancy, and denial of the pregnancy. Logistic regression analysis reveals that the odds of a pregnancy being unwanted if the baby was of low birth weight were greater for the following factors: smoking during pregnancy, maternal age, race, education, health status, pre-pregnancy weight-for-height, parity, infant mortality, and in-patient status at the survey date. The sample included 42% of mistimed pregnancies, and 15% each reported the pregnancy as unwanted, unhappy, or a denial. Birth weight outcomes did not vary by age or race. Low birth weight did not differentiate the wantedness of pregnancies using the timing-wantedness scale, but did distinguish on the happiness scale and denial measures.

Factors associated with repetition of low birthweight: Missouri longitudinal study.

The tendency to repeat low birthweight (LBW < 2500 g) was studied in 182,285 linked first and second birth Missouri livebirths for 1978-90, of which 10,701 had first birth LBW. We examined the likelihood of LBW repetition by first birth birthweight, preterm delivery, and small-for-gestational-age (SGA) status by race, and the odd ratios (ORs) of repeat LBW for risk factors such as smoking, in comparison with ORs of second birth LBW among women with normal-weight first births. We found a strong tendency to repeat LBW (21%), especially following more extreme LBW first births. Adjusted ORs for repeat LBW were 10.1 for births that were preterm and SGA; 7.9 for preterm non-SGA; and 6.3 for SGA term births. Significant ORs of LBW repetition were found for smoking (1.52 and 1.85 for smoking in second pregnancy only and both pregnancies, respectively), short interpregnancy interval (1.33), and advanced maternal age (1.17), but the ORs were generally lower than those for women with normal-weight first births. Low pre-pregnancy weight was a significant risk factor for LBW repetition.

Prevalence and implications of perinatal substance use in Missouri.

A study was conducted to determine the prevalence of perinatal substance use in Missouri. The population sample studied was selected according to a multi-stage probability-proportional-to-size sampling. The weighted prevalence for perinatal exposure to alcohol, tobacco or illicit substances was 31.9%, 10.8% for illicit substances, 21.9% for tobacco use, and 7.9% for self-reported alcohol use. In 1993, an estimated 23,925 perinatal exposures to licit and illicit substances occurred.

Exercise, employment, other daily activities, and adverse pregnancy outcomes.

The relations of exercise, employment, and other daily activities during pregnancy with pregnancy outcomes were examined using data from the Missouri Maternal and Infant Health Survey. Maternal surveys were available for the following singleton birth categories: 450 fetal deaths; 782 very low birth weight (VLBW, < 1,500 g); 802 moderately low birth weight (MLBW, 1,500-2,499 g); and 794 normal birth weight (NBW, > or = 2,500 g). All mothers were Missouri residents at the time of their December 1989 to March 1991 deliveries. It was found that VLBW mothers had exercised during pregnancy significantly less than NBW mothers. When compared with NBW mothers before pregnancy, VLBW mothers had been just as likely not to exercise as NBW mothers (odds ratio (OR) = 0.88, 95% confidence interval (CI) 0.69-1.12). During the first, second, and third trimesters, the odds ratios decreased to 0.70 (95% CI 0.53-0.92), 0.54 (95% CI 0.40-0.74), and 0.33 (95% CI 0.20-0.53), respectively. The VLBW mothers also were less likely to exercise during the third trimester than MLBW mothers (OR = 0.34, 95% CI 0.21-0.54) or mothers with fetal deaths (OR = 0.36, 95% CI 0.19-0.67). During the 3 months after pregnancy, none of the exercise odds ratios were statistically significant between groups. No significantly increased risks were found between employment during pregnancy or other daily activities and adverse pregnancy outcome. The study supports the recently relaxed guidelines of exercise during pregnancy.

Selected antepartum medical complications and very-low-birthweight infants among black and white women.

This study estimated the risk of very-low-birthweight delivery among Black and White women with selected treatable antepartum medical conditions. A logistic regression model was applied to a retrospective, population-based data set identified by computerized, linked birth certificate and maternal hospital discharge records. For Black mothers, the adjusted odds ratio for very-low-birthweight delivery was statistically significant for essential hypertension and urinary tract infection. For White mothers, the adjusted odds ratio was statistically significant for essential hypertension, urinary tract infection, pregnancy-induced hypertension, and diabetes mellitus. Public policy designed to reduce the risk of very-low-birthweight delivery must include strategies for attenuating the impact of treatable antepartum medical conditions.

Smoking and pregnancy outcome: trends among black teenage mothers in Missouri.

OBJECTIVES: The purpose of this study is to analyze the smoking changes that have occurred among pregnant Black teenagers in Missouri. The study also examines changes in Black teenage pregnancy outcomes in relation to smoking behavior changes. METHODS: This analysis used computerized data files from the 1978 to 1990 Missouri birth certificates to acquire information on smoking during pregnancy for 41,544 Black teenagers and 105,170 White teenagers. All Missouri births with smoking history were included in the study. RESULTS: During the study period, the rate for Blacks who smoked during pregnancy decreased from 37% in 1978 to less than 22% in 1990. A large part of this reduction is attributable to Black teenagers, whose smoking-during-pregnancy rate declined from 35.8% to 7.2%. Additionally, the Black teenage-specific low-birthweight rate decreased by 13.6% over the study period, possibly influenced by the decrease in smoking. CONCLUSIONS: The results indicate that a major norm has changed in smoking status among pregnant Black teenagers. Understanding the reasons behind this change could assist smoking cessation and other health promotion efforts.

Changes in characteristics of women who smoke during pregnancy: Missouri, 1978-88.

The Missouri birth certificate has had a question, "cigarettes smoked per day?" since 1978; the current data base contains more than 800,000 records. A comparison of the Missouri data for married mothers with the National Natality Survey (NNS) data shows mainly consistent findings between the two data sets. The Missouri data, however, also provided information on the smoking status during pregnancy of unmarried women that is not available from the NNS. The Missouri data show a substantial difference in the smoking rates of married (23.2 percent) and unmarried (40.9 percent) women. The highest smoking rates during pregnancy are found among unmarried women, ages 20-24, with less than a high-school education, and those with a fourth or higher order child. There has been a relatively small overall drop in the smoking rate from 1978-80 to 1986-88 (31.1 percent versus 27.5 percent). However, blacks and teenagers have had very substantial drops in smoking rates. There has been only a slight decrease for other high-risk groups such as white unmarried women, women with less than a high-school education, and those having a fourth or higher order birth. Missouri started using the new national standard birth certificate in 1989 with a differently worded smoking question. The percentage of women smoking and those smoking less than one pack per day in 1989 went down more than would be expected from the trend data. It appears that the new birth certificate question will provide a lower estimate of the percentage of mothers who smoke cigarettes than was acquired from the previous version on the Missouri certificate. The births in Missouri for which mothers' rate of smoking was unknown increased nearly fourfold to 0.9 percent.

Differentiating the barriers to adequate prenatal care in Missouri, 1987-88.

Inadequate prenatal care has previously been identified as a significant risk factor for women who have low birth weight infants and infants who die during the neonatal period. Postpartum interviews with 1,484 primarily low-income women were conducted during 1987-88 in three areas of Missouri with the highest rates of inadequate prenatal care. The purpose of the study was to identify barriers to prenatal care and to determine which barriers differentiated between women receiving adequate and those receiving inadequate prenatal care. Women who received inadequate prenatal care were more likely to be black, unmarried, higher parity, and have less education than those who received adequate care. These women were also more likely to be poor, Medicaid-eligible, to have had an unwanted pregnancy, more stress and problems during pregnancy, and less social support. In the multivariate analysis, race and marital status lost their importance. The strongest predictor of inadequate prenatal care was women not knowing that they were pregnant in the first 4 months of pregnancy (adjusted odds ratio 9.28). To improve the rate of adequate prenatal care, society must address the issues of poverty and wantedness of pregnancy.

Reproductive outcomes of mothers with potential exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Animal laboratory studies have demonstrated that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has fetotoxic and teratogenic effects at low doses. TCDD contamination of soil in nine residential areas of eastern Missouri began in 1971 when several horse arenas and dirt roads were sprayed for dust control with a mixture that contained waste oil and dioxin. The authors conducted an epidemiologic investigation to determine if adverse human reproductive outcomes are associated with exposure to soil contaminated with dioxin. The authors attempted to identify all births during the period of January 1, 1972 through December 31, 1982 that had potential exposure to dioxin, based on proximity of the maternal address to a location of known TCDD contamination. This group totaled 410 births. A matched set of 820 unexposed births was selected as a comparison group after being matched for maternal age and race, year of birth, hospital of birth, and plurality. The exposed group had increased risk ratios for infant, fetal, and perinatal death; low birth weight; and several subcategories of birth defects. None of these increased risk ratios for the exposed group were statistically significant. These results do not provide evidence that TCDD exposure has a substantial impact on the reproductive outcomes investigated. If TCDD does produce effects on reproductive health, a larger study and/or better measures of exposure may be needed to discover them.

WIC prenatal participation and its relation to pregnancy outcomes in Missouri: a second look.

We studied the association of WIC prenatal supplementation with pregnancy outcome using Missouri WIC participants who delivered in 1982 linked with their offspring's birth/fetal death certificates. A 93 per cent match rate resulted in a final study population of 9,411 pregnancies. A control population of like number was acquired by matching on key demographic characteristics. The majority of the results generally confirm the results of a 1980 Missouri study; WIC participation was associated with decreases in low birthweight (7.8 vs 9.2 per cent), prematurity (9.7 vs 12.0 per cent) and inadequate prenatal care (30.5 vs 31.7 per cent), and an increase in mean gestational age (39.9 vs 39.6 weeks). Low birthweight rates were lower for infants of WIC participants in each of the risk categories reviewed. As noted in the 1980 study, duration of WIC of at least seven months was needed before improvements in birthweight outcomes measures were noted.

Evaluation of the Missouri WIC program: prenatal components.

A study was performed to evaluate the prenatal components of the Missouri Special Supplemental Food Program for Women, Infants and Children (WIC) Program. The study used WIC prenatal participants delivering in 1980 and their offspring's birth/fetal death certificates. A 93% match rate was acquired with a final study population of 6,732. Three basic methods of overall analysis were used to acquire a comparison group: covariate analysis, standardization, and pair matching. A higher mean birth weight was noted for the WIC total and WIC non-white group when the method of analysis was covariate or standardization; the latter was statistically significant. In either instance, the amount of increase was small. A reduced low-birth-weight rate was noted for the WIC total and the WIC non-white group regardless of the method of analysis used; the differences were statistically significant for the standardization method. Duration in WIC had a positive influence on both mean birth weight and low birth weight, regardless of race. High-risk groups used for program participation also were analyzed. Overall, this study showed that WIC prenatal nutritional supplementation has a positive, though not conclusive, impact on reducing low birth weight and raising mean birth weight.

Perinatal deaths in twin pregnancy. A five-year analysis of statewide statistics in Missouri.

Analysis of computer-stored State of Missouri birth and death records over a 5 year period revealed 3,594 twin pregnancies (1.02% of all pregnancies), which accounted for 10.1% of the perinatal deaths. The mean birth weight according to weeks of gestation was computed for the pregnancies with no complications noted prior to labor and the perinatal mortality rate was determined. Complications of pregnancy were evaluated. Low birth weight appears to be the major factor in the elevated perinatal death rate in twin pregnancy, with a significant elevation of the perinatal death rate noted with labor prior to 36 weeks, any episode of hemorrhage, or premature rupture of membranes. A more liberal use of cesarean section currently shows no effect in altering the perinatal mortality rate. Programs are suggested to increase early detection and appropriate consultation and referral of multiple pregnancies in a statewide comprehensive effort to decrease the perinatal mortality rate in twin pregnancy.