Trends in Pregnancy Weight Gain Within and Outside Ranges Recommended by the Institute of Medicine in a WIC Population

Objectives: To examine the proportion of women with a pregnancy weight gain below, within, and above ranges recommended by the Institute of Medicine from 1990 to 1996. Methods; Our study population included women attending Special Supplemental Nutrition Program for Women, Infants and Children (WIC) clinics in five states who delivered a liveborn singleton infant at term (N = 120,531). Pregnancy weight gain was self-reported at the postpartum visit Results: Only 34% of women gained weight within recommended ranges and there was little change in this proportion from 1990 to 1996. The proportion of women gaining less than their recommended weight decreased from 23.4% to 22.0%, and the proportion gaining more than recommended increased from 41.5% to 43.7% during the study period. Stratified analyses revealed similar trends within all race-ethnicity, age, parity, trimester of WIC initiation, and trimester of prenatal care initiation strata and among women in low, average, and high prepregnancy body mass index categories. There was no change in the weight gain distribution among obese women. Absolute and relative increases in the proportion of women gaining more weight than recommended were greatest among women who were underweight, Asian or Native American, less than 20 years of age, multiparous, and who initiated WIC and prenatal care in the third trimester. Conclusions: Pregnancy weight gain increased among this population of WIC participants from 1990 to 1996.     

Timing of Enhanced Prenatal Care and Birth Outcomes in New Jersey’s HealthStart Program

Objective: This study examined the effects of prenatal care and the timing of its initiation on birth weight and gestational age outcomes among women in a state-wide Medicaid enhanced prenatal care program. Methods: Ordinary Least Squares and logistic regression analyses were performed using data on 88,196 births in New Jersey between 1988 and 1996. A large number of potentially confounding factors were included. Results: Initiating prenatal care in the first trimester was associated with a 56 g advantage in birth weight (p = .01) compared to no care. Initiating prenatal care in the first or second trimester was associated with a 1 day advantage in gestational age (p = .05). There were no significant effects of prenatal care, initiated in any trimester, on low-birth weight. Initiating care in the first versus the second trimester had no effect on the probability of delivering preterm. The findings did not vary by sociodemographic subgroup. Conclusion: This study provides support for claims that there is little that prenatal care can do to improve aggregate birth outcomes because most pregnancy complications are the result of behaviors and life circumstances that precede the pregnancy and are very difficult to reverse. Prenatal care, even with enhanced services, appears to offer too little, too late.     

A Comparative Analysis of Effects of Early Versus Late Prenatal WIC Participation on Birth Weight: NYS, 1995

OBJECTIVES: This study examined the effects of prenatal participation in the NYS WIC Program on birth weight through enhanced control of selection bias and gestational age bias. Program effects were assessed separately for White, Black, and Hispanic women and subpopulations defined by values of Kotelchuck index of adequacy of prenatal care utilization. METHODS: 1995 New York State Vital Statistics records were linked to WIC certifications, administrative and check redemption files, and to the 1990 federal census of NY county level data. The final data set contained 77,601 records. Birth weight among WIC participants who enrolled early and participated longer were compared to those who enrolled late and participated a shorter time. Selection bias was addressed using classification tree methods as part of a propensity score analysis. Gestational age bias was addressed by analyzing preterm and full-term pregnancies separately. RESULTS: Adjusted estimates showed a significant positive effect of longer prenatal WIC participation on birth outcomes for all groups studied. Infants born to WIC participants who enrolled early were heavier than those who enrolled late by, on average, 70 g for full-term and 129 grams for preterm. Black and Hispanic full-term infants experienced larger WIC effects than Whites (79, 75, 43 g, respectively). Looking at full-term pregnancies using Kotelchuck's index indicated that effects of longer prenatal WIC participation were greatest for the inadequate prenatal care group (83 g). CONCLUSION: Longer prenatal WIC participation was associated with an increase in birth weight overall and for all groups studied. The effect on birth weight of longer participation in WIC was greatest in Black and Hispanic, inadequate and no prenatal care groups.     

The impact of short interpregnancy intervals on pregnancy outcomes in a low-income population.

OBJECTIVES: The objective of this study was to determine whether the length of the interval between pregnancies was associated with either preterm birth or intrauterine growth retardation in a low-income, largely Black population. METHODS: The study population consisted of 4400 women who had received prenatal care in county clinics and had two consecutive singleton births between 1980 and 1990. RESULTS: Interpregnancy intervals were positively associated with age and negatively associated with the trimester in which care was initiated in the second pregnancy. Whites had shorter intervals than non-Whites. The percentage of preterm births increased as the length of the interpregnancy interval decreased, but only for women who had not had a previous preterm birth. The association between interval and preterm birth was maintained when other factors associated with preterm birth were controlled. There was no significant relationship between intrauterine growth retardation and interpregnancy interval. CONCLUSIONS: Women, particularly those who are poor and young, should be advised of the potential harm to their infants of short interpregnancy intervals.     

Within prisons,is there an association between the quantity of prenatal care and infant birthweight?

There is still controversy surrounding the effectiveness of prenatal care in reducing low birthweight. In addition, very few studies have assessed the relationship between prenatal care and infant birthweight among pregnant women within the prison system. We sought to ascertain whether there is an association between the quantity of prenatal care and infant birthweight among pregnant women within such a setting. We examined the prison medical records of 147 infants born to women delivering at term (37-41 weeks of gestation) between 1 January 2002 and 31 December 2004 who were incarcerated during pregnancy in Texas state prisons. Linear regression was used to evaluate the association between the number of prison prenatal care visits and infant birthweight while adjusting for potential confounders (age, gravidity, maternal education, maternal race, history of substance use, history of alcohol use, history of tobacco use and the presence of any chronic disease). We also adjusted for the interaction between the gestational age at admission to prison and the number of prison prenatal care visits. There was a statistically significant 120.5 g increase in adjusted mean birthweight with each additional prison prenatal care visit (P = 0.001) among study infants whose mothers entered prison during the first trimester. This trend was not observed among women who came in after the first trimester. There appears to be a positive association between the amount of prison prenatal care and infant birthweight among incarcerated pregnant women delivering at term, but this association appears to be limited to women entering prison during the first trimester of pregnancy.     

Prenatal active or passive tobacco smoke exposure and the risk of preterm delivery or low birth weight

We examined the association of exposure to environmental tobacco smoke with birth weight and gestational age in a large, prospective study. We also compared these endpoints between infants of active maternal smokers and those of non-smoking, non-ETS exposed women. Pregnant women were interviewed by telephone during the first trimester, and pregnancy outcome was determined for 99%. Among the 4,454 singleton live births that could be linked to their birth certificate, we confirmed increased risks of low birth weight and small for gestational age with heavier maternal smoking (> 10 cigarettes/day), as well as noting an increased risk for "very preterm" birth (< 35 weeks). These associations were generally stronger among infants of older (> or = 30 years) than those of younger mothers, as well as among non-whites. High environmental tobacco smoke exposure (> or = 7 hours/day in non-smokers) was moderately associated with low birth weight (adjusted odds ratio (AOR) 1.8, 95% confidence limits (95% CL) = 0.82, 4.1), preterm birth (AOR 1.6, 95% CL = 0.87, 2.9), and most strongly with very preterm birth (AOR 2.4, 95% CL = 1.0, 5.3). These associations were generally greater among non-whites than whites. The data support earlier studies suggesting that prenatal environmental tobacco smoke exposure, in addition to maternal smoking, affects infant health.     

Savings achieved by giving WIC benefits to women prenatally.

The Special Supplemental Food Program for Women, Infants, and Children (WIC) provides supplemental food, nutrition and health education, and social services referral to pregnant, breastfeeding, and post-partum women, and their infants and young children who are both low-income and at nutritional risk. A number of statistically controlled evaluations that compared prenatal women who received WIC services with demographically similar women who did not receive WIC services have found WIC enrollment associated with decreased levels of low birth weight among enrolled women''s infants. Several also have found lower overall maternal and infant hospital costs among women who had received prenatal WIC services compared with similar women who did not receive prenatal WIC services. A meta-analysis of the studies shows that providing WIC benefits to pregnant women is estimated to reduce low birth weight rates 25 percent and reduce very low birth weight births by 44 percent. Using these data to estimate costs, prenatal WIC enrollment is estimated to have reduced first year medical costs for U.S. infants by $1.19 billion in 1992. Savings from a reduction in estimated Medicaid expenditures in the first year post-partum more than offset the cost of the Federal prenatal WIC Program. Even using more conservative assumptions, providing prenatal WIC benefits was cost-beneficial. Because of the estimated program cost-savings, the U.S. General Accounting Office has recommended that all pregnant women at or below 185 percent of Federal poverty level be eligible for the program.     

Risk of oral clefts in relation to prepregnancy weight change and interpregnancy interval

Epidemiologic evidence regarding the influence of maternal obesity on the risk of oral clefts is inconsistent. It is unknown whether increases in maternal weight before pregnancy are related to the risk of these malformations. The authors conducted a population-based cohort study in Sweden among 220,328 women who had their first two pregnancies between 1992 and 2004. The risk of oral clefts during the second pregnancy was estimated in relation to maternal change in body mass index (BMI; weight (kg)/height (m)(2)) from the beginning of the first pregnancy to the beginning of the second pregnancy. Among women whose second-pregnancy BMI was > or =3 units higher than their first-pregnancy BMI, the adjusted risk of isolated cleft palate was 2.3 times higher (95% confidence interval: 1.4, 4.0) as compared with women whose BMI did not change substantially. BMI change was not related to the risk of cleft lip. Unexpectedly, the birth prevalence of isolated cleft palate per 1,000 livebirths increased linearly with the length of the interpregnancy interval, from 0.3 in women with intervals of <12 months to 0.9 in women with intervals of > pr =48 months (adjusted p for trend = 0.002). High prepregnancy maternal weight gain and long interpregnancy intervals appear to be associated with increased risk of cleft palate.     

Factors influencing early prenatal enrollment in the WIC program

Women's access to prenatal nutrition services was explored using a nationally representative sample of pregnant participants in the Special Supplemental Food Program for Women, Infants, and Children (WIC) in 1984. The probability was examined of the participant entering the program during her first trimester, rather than the second or third trimester. Other research has suggested that length of participation in the program during pregnancy is associated with increased birth weight. The data were adjusted for various personal and local operational factors, such as prior WIC participation, race, age, income, household size, WIC priority level, availability of prenatal or other health services, targeted outreach policies, years of local operation, and local agency size. Previous participation in the WIC Program was the only factor significantly associated with early enrollment (adjusted odds ratio 2.1). Race was marginally significant. Neither the presence of local policies of outreach targeted to pregnant women, nor co-location of WIC services with prenatal or other health services, showed significant effects on early enrollment.     

The Influence of Site of Care on the Content of Prenatal Care for Low-Income Women

Objective: To assess whether site of prenatal care influences the content of prenatal care for low-income women. Design: Bivariate and logistic analyses of prenatal care content for low-income women provided at five different types of care sites (private offices, HMOs, publicly funded clinics, hospital clinics, and other sites of care), controlling for sociodemographic, behavioral, and maternal health characteristics. Participants: A sample of 3405 low-income women selected from a nationally representative sample of 9953 women surveyed by the National Maternal and Infant Health Survey, who had singleton live births in 1988, had some prenatal care (PNC), Medicaid participation, or a family income less than $12,000/year. Outcome Measures: Maternal report of seven initial PNC procedures (individually and combined), six areas of PNC advice (individually and combined), and participation in the Women Infant Children (WIC) nutrition program. Results: The content of PNC provided for low-income women does not meet the recommendations of the U.S. Public Health Service, and varies by site of delivery. Low-income women in publicly funded clinics (health departments and community health centers) report receiving more total initial PNC procedures and total PNC advice and have greater participation in the WIC program than similar women receiving PNC in private offices. Conclusions: Publicly funded sites of care appear to provide more comprehensive prenatal care services than private office settings. Health care systems reforms which assume equality of care across all sites, or which limit services to restricted sites, may foster unequal access to comprehensive PNC.     

Clustering of U.S. Women Receiving No Prenatal Care: Differences in Pregnancy Outcomes and Implications for Targeting Interventions

Objectives: Prenatal care is an established mechanism for identifying and managing risk factors impacting pregnancy outcomes. Despite aggressive efforts in the United States (US) to assure that all women begin care in the first trimester, every year about 70,000 women in the US receive no care prior to delivery. We hypothesized that US women receiving no prenatal care comprise clusters (subgroups) with distinctive behavioral, socio-demographic, and medical risks and that birth outcomes differ among the clusters. Methods: White, Black, and Hispanic women (n = 126,220) receiving no prenatal care and delivering a live, singleton infant were identified from linked birth and death certificates for years 1995 through 1997. Cluster analysis was used to group women with similar characteristics, and cluster assignment was evaluated using discriminant analysis. Birth outcomes for any care and no-care women were then examined using logistic regression. Results: Six replicable clusters of women with no care were identified. Birth outcomes varied significantly among clusters and were two to four times worse for no-care clusters compared to outcomes for women receiving any care. Conclusions: Cluster analysis is an effective alternative for grouping individuals for use in public health education, intervention, and outreach programming. Women receiving no prenatal care were characteristically different from women receiving any care in this study, but they did not represent a homogenous group. Findings suggest that interventions should target reducing the proportion of women receiving no care and should be tailored to specific no-care clusters.     

Integrating Obstetrical Care and WIC Nutritional Services to Address Maternal Obesity and Postpartum Weight Retention

Objective

This pilot study evaluated a cost neutral, integrated Special Supplemental Nutrition Program for Women Infants and Children (WIC) and obstetrical service model designed to prevent postpartum weight retention in obese women.

Methods

A sample of women who received benefits from the Johns Hopkins (JH) WIC program and prenatal care from the JH Nutrition in Pregnancy Clinic, which provides obstetrical care for women with a BMI?≥?30 kg/m², participated in the WICNIP randomized clinical trial. Intervention participants received enhanced nutrition services and education at five visits and during one phone call between delivery and 6 months postpartum. Control participants received standard WIC services. Weight data was collected for all participants at multiple time points: pre-pregnancy, delivery, and postpartum at 4, 6 weeks, 4, and 6 months. Maternal socio-demographic factors, obesity class and the number of education contacts received were also recorded.

Results

Fifty-three African-American women were randomized into the intervention and control groups. Intervention participants retained significantly less gestational weight gain than control participants (3.0?±?11.8 vs. 12.6?±?20.4, p?<?0.05). In both groups, participants with Class III obesity retained significantly less weight than participants in Classes I and II (p?=?0.02).

Conclusions for Practice

An integrated WIC and obstetrical service model is feasible and can limit postpartum weight retention in obese women. Weight retention at 6 months postpartum between intervention and control participants was statistically significant. Further research should explore targeted interventions by obesity class to address weight retention for low-income, African American women who participate in WIC.

     

Individual and Community Level Correlates of Prenatal Care in California

This event history analysis of the Perinatal Substance Exposure Study investigates individual and community level correlates of the timing of first prenatal care among pregnant women in California. Data were collected anonymously at the time of delivery and include demographic information from hospital records and urine samples which were tested for a battery of substances. Zip-code level data from the 1990 census were appended to each record to assess absolute community effects. A discrete-time hazard rate was estimated for each trimester in six nested models using logistic regression. Results suggest that: poor, non-White, younger, native born, Spanish-speaking, substance-using women in poorer neighborhoods were least likely to receive prenatal care. While a positive urine test for alcohol was not associated with prenatal care initiation; overall drug positives and tobacco positives (self-report) were. The optimal model, with interactions, estimates that women in poorer communities were less likely to receive prenatal care in the first trimester, but more likely to receive care in the third trimester. This pattern is similar for most of the time-varying covariates in that non-Whites, English speakers and younger women were less likely to receive first trimester care, but more likely to receive second and third trimester care.     

Pregnancy-Associated Obesity in Black Women in New York City

Objective: To determine weight gain during pregnancy and weight changes postpartum in first-time mothers delivering at or near term. Methods: At about 2 weeks after delivery, 47 adult, Black and Hispanic women provided information on their prepregnancy weight and height and maximum pregnancy weight. Women reinterviewed at 2 and 6 months after delivery reported their most recent weight measurement and the date of that measurement. This information was used to compute each woman's prepregnancy body mass index, pregnancy weight gain, and weight loss postpartum. Information on infant feeding was also collected at each postpartum visit. Results: About 2/3 of the women and 100% of the overweight and obese women gained excessive weight during pregnancy. Weight gain was most marked in women who started pregnancy overweight or obese. At 2 months postpartum, women were on average almost 18 lb above their prepregnancy weight. No additional maternal weight was lost by 6 months postpartum. Most infants were started on formula by 2 weeks of age. At 2 months of age, 85% were fed formula only and 91% of the infants were on WIC. Conclusions: Our results demonstrate a need for interventions to help women avoid obesity by regulating their pregnancy weight gain, losing weight for a longer period postpartum, and initiating and maintaining exclusive breast-feeding.     

First- and Second-Trimester WIC Participation Is Associated with Lower Rates of Breastfeeding and Early Introduction of Cow's Milk during Infancy

Background

Existing literature suggests prenatal participation in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) may reduce breastfeeding among low-income mothers. However, little is known about whether the timing of WIC entrance during pregnancy influences infant feeding decisions.

Objective

This study assesses the association between the timing of prenatal participation in WIC and various infant feeding practices, including breastfeeding initiation, breastfeeding for at least 4 months, exclusive breastfeeding, formula feeding, and early introduction of cow's milk and solid food.

Design

Cross-sectional survey matching of birth certificate data to mothers' interviews 9 months after the child's birth. Mothers provided information on participation in the WIC program, infant feeding practices, and sociodemographic characteristics.

Subjects

A nationally representative sample of 4,450 births in 2001 from the Early Childhood Longitudinal Survey-Birth Cohort.

Analyses

Multivariate logistic regression techniques (using STATA 9.0 SE, Stata Company, College Station, TX) estimated the relationship between the timing of prenatal WIC participation and infant feeding practices.

Results

Entry into the WIC program during the first or second trimester of pregnancy is associated with reduced likelihood of initiation of breastfeeding and early cow's milk introduction; and entry during the first trimester is associated with reduced duration of breastfeeding. WIC participation at any trimester is positively related to formula feeding.

Conclusions

Prenatal WIC participation is associated with a greater likelihood of providing babies infant formula rather than breastmilk after birth. Findings also indicate that there are critical prenatal periods for educating women about the health risks of early cow's milk introduction. Given the health implications of feeding infants cow's milk too early, WIC may be successful in educating women on the health risks of introducing complementary foods early, even if direct counseling on cow's milk is not provided.     

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.     

Pregnancy nutrition surveillance system--United States, 1979-1990.

Since 1979, the CDC Pregnancy Nutrition Surveillance System (PNSS) has monitored behavior and nutritional risk factors among low-income pregnant women participating in public health programs. Although the states contributing to the system have varied over the period, the PNSS is able to characterize the behavior and health outcomes of pregnant women from diverse low-income populations. In 1990, 66.2% of the women in the system initiated prenatal care during the first trimester of pregnancy; 26.4% smoked during pregnancy. Since 1979, the prevalence of smoking remained relatively stable for white women, but declined for blacks and Hispanics. Prepregnancy body mass index (BMI, defined as kg/m2) showed marked changes from 1979 through 1990; the prevalence of underweight (BMI < 19.8) declined steadily and the prevalence of overweight (BMI > 26) increased steadily. In 1990, 39.3% of the women had gestational weight gains below levels recommended by the National Academy of Sciences. Both prepregnancy underweight and inadequate gestational weight gain were associated with greater risk for low birth weight in the PNSS. The prevalence of anemia at each trimester has remained stable since 1979. In 1990, 9.8%, 13.8%, and 33% of the women reported by the PNSS were anemic in the first, second, and third trimesters, respectively. Anemia in the first trimester appeared to be strongly associated with a high risk of low birth weight; this association was attenuated in later trimesters. These findings indicate the need to improve iron nutrition among low-income women.     

Maternal Smoking and the Timing of WIC Enrollment

Objective: To investigate the association between the timing of enrollment in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and smoking among prenatal WIC participants. Methods: We use WIC data from eight states participating in the Pregnancy Nutrition Surveillance System (PNSS). We adjust the association between the timing of WIC participation and smoking behavior with a rich set of maternal characteristics. Results: Women who enroll in WIC in the first trimester of pregnancy are 2.7% points more likely to be smoking at intake than women who enroll in the third trimester. Among participants who smoked before pregnancy and at prenatal WIC enrollment, those who enrolled in the first trimester are 4.5% points more likely to quit smoking 3 months before delivery and 3.4% points more likely to quit by postpartum registration, compared with women who do not enroll in WIC until the third trimester. However, among pregravid smokers who report quitting by the first prenatal WIC visit, first-trimester enrollment is associated with a 2% point increase in relapse by postpartum registration. These results differ by race/ethnicity; white women who enroll early are 3.6% points more likely to relapse, while black women are 2.5% points less likely to relapse. Conclusions: Early WIC enrollment is associated with higher quit rates, although changes are modest when compared to the results from smoking cessation interventions for pregnant women. Given the prevalence of prenatal smoking among WIC participants, efforts to intensify WIC’s role in smoking cessation through more frequent, and more focused counseling should be encouraged.     

Delayed prenatal care and the risk of low birth weight delivery

To determine if the timing of prenatal care is associated with low birth weight delivery after adjusting for sociodemographic and behavioral risk factors, we performed a retrospective cross-sectional study of singleton births to white (2,945,595) or African-American (552,068) women in the United States in 1996. When adjusted for race, maternal age, educational level attained, and the use of alcohol and tobacco during pregnancy, women beginning care in the 2nd (adjusted RR = 0.85; 95% CI: 0.83–0.86) and 3rd trimesters (RR = 0.87; 95% CI: 0.84–0.91) had a reduced risk of low birth weight compared to women beginning care in the 1st trimester. Our findings suggest that no benefit exists for early initiation of prenatal care for reducing the risk of low birth weight. Findings related to differences in low birth weight among women who start prenatal care later are likely due to sociodemographic differences that may influence access to early care.