The relationship between water intake and foetal growth and preterm delivery in a prospective cohort study.

BACKGROUND: Interpretation of previous associations between water intake and adverse birth outcomes is challenging given that amount and type of water consumed can be non-specific markers of exposure or underlying behavioural characteristics. We examined the relationship between water intake measures and adverse birth outcomes in participants from three study sites in the United States. METHODS: Using a prospective cohort study, we examined daily intake of bottled, cold tap, total tap, and total water in relation to birth weight and risk of small-for-gestational-age (SGA) among term births and risk of preterm delivery. RESULTS: Based on water consumption data collected between 20-24 weeks of gestation, the adjusted mean birth weight was 27 (95% confidence interval [CI]: -34, 87), 39 (95% CI: -22, 99), and 50 (95% CI: -11, 110) grams higher for the upper three total water intake quartiles (> 51-78, > 78-114, and > 114 ounces/day) compared to the lowest quartile (≤ 51 ounces/day). Adjusted birth weight results were similar for bottled water, cold tap water, and total tap water intake. An exposure-response gradient was not detected for either preterm delivery or SGA with increasing total water intake and total tap water intake, but adjusted relative risks for all three upper quartiles were below 1.0 (range: 0.6-0.9) for SGA. CONCLUSION: These data suggest that high water intake may be associated with higher mean birth weight following adjustment for confounding.

Comparison of gestational age at birth based on last menstrual period and ultrasound during the first trimester.

Reported last menstrual period (LMP) is commonly used to estimate gestational age (GA) but may be unreliable. Ultrasound in the first trimester is generally considered a highly accurate method of pregnancy dating. The authors compared first trimester report of LMP and first trimester ultrasound for estimating GA at birth and examined whether disagreement between estimates varied by maternal and infant characteristics. Analyses included 1867 singleton livebirths to women enrolled in a prospective pregnancy cohort. The authors computed the difference between LMP and ultrasound GA estimates (GA difference) and examined the proportion of births within categories of GA difference stratified by maternal and infant characteristics. The proportion of births classified as preterm, term and post-term by pregnancy dating methods was also examined. LMP-based estimates were 0.8 days (standard deviation = 8.0, median = 0) longer on average than ultrasound estimates. LMP classified more births as post-term than ultrasound (4.0% vs. 0.7%). GA difference was greater among young women, non-Hispanic Black and Hispanic women, women of non-optimal body weight and mothers of low-birthweight infants. Results indicate first trimester report of LMP reasonably approximates gestational age obtained from first trimester ultrasound, but the degree of discrepancy between estimates varies by important maternal characteristics.

Drinking water disinfection by-product exposure and fetal growth.

BACKGROUND: Previous studies suggest that elevated exposure to drinking water disinfection by-products (DBPs)--in particular, total trihalomethanes (TTHMs)--may lead to fetal growth restriction. We examined the effects of exposure to TTHMs, haloacetic acids, and total organic halide on the probability of delivering a small-for-gestational-age (SGA) infant and on birth weight at term. METHODS: Women early in pregnancy (< or =12 weeks' gestation) or planning a pregnancy were enrolled in a prospective pregnancy study conducted in 3 US communities from 2000 through 2004. Weekly (or biweekly) water samples were collected at each site as well as individual-level participant data. Associations between DBP exposures (TTHMs, haloacetic acids, total organic halide) and fetal growth were assessed using log-binomial regression for SGA (n = 1958) and linear regression for term birth weight (n = 1854). We conducted a Bayesian analysis to examine associations between individual DBP species and fetal growth. RESULTS: Haloacetic acids and total organic halide were not associated with SGA or term birth weight. The probability of delivering an SGA infant was elevated when comparing women with an average third-trimester residential TTHM concentration > or =80 microg/L to women with exposure <80 microg/L (risk ratio = 2.0 [95% confidence interval = 1.1-3.6]), but not when examining other exposure contrasts. Bayesian analyses did not support a consistent association between any DBP species and fetal growth, although these analyses were based on small sample sizes. CONCLUSIONS: Our results do not suggest an adverse effect of haloacetic acid or total organic halide exposure on fetal growth. An association of TTHM with SGA was seen only for average residential concentrations above the current regulatory standard.

Drinking water disinfection by-product exposure and duration of gestation.

BACKGROUND: Recent studies suggest elevated exposure to drinking water disinfection by-products (DBPs) may be associated with decreased risk of preterm birth. We examined this association for exposure to total trihalomethanes (TTHMs), 5 haloacetic acids (HAA5), and total organic halides. METHODS: Analysis included 2039 women in a prospective pregnancy study conducted from 2000 through 2004 in 3 study sites. Water samples were collected and analyzed for DBP concentrations. Participant data were collected through interviews, an early ultrasound, and birth records. We assessed the associations between DBPs and preterm birth (<37-weeks' gestation) using log-binomial regression. Discrete-time hazard analysis was used to model the conditional odds of delivery each week in relation to DBP exposure. RESULTS: Average second trimester DBP levels were associated with lower risk of preterm birth. Adjusted risk ratios for TTHM levels of 33.1-55.0, 55.1-66.3, 66.4-74.8, and 74.9-108.8 microg/L versus 2.2-4.6 microg/L were 0.8 (95% confidence intervals = 0.5-1.3), 0.9 (0.6-1.4), 0.7 (0.4-1.1), and 0.5 (0.3-0.9), respectively. Risk ratios for HAA5 levels of 17.9-22.0, 22.1-31.5, 31.6-40.4, and 40.5-52.8 microg/L versus 0-0.9 microg/L were 1.1 (0.8-1.7), 0.8 (0.5-1.2), 0.5 (0.3-0.8), and 0.7 (0.4-1.1), respectively. The conditional odds of delivery each week were decreased for the highest TTHM and HAA5 exposure groups versus the low exposure group for gestational weeks 33-40. CONCLUSIONS: The probability of preterm birth was not increased with high DBP exposure.

Endometriosis among women exposed to polybrominated biphenyls.

PURPOSE: We examined the association between endometriosis and exposure to polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) among women inadvertently exposed to PBBs in 1973. METHODS: Serum PBBs and PCBs were measured in the late 1970s. Women self-reported endometriosis at interview in 1997. We constructed Cox models to estimate the relative incidence of endometriosis in relation to PBB and PCB levels. RESULTS: Seventy-nine of 943 women (9%) reported endometriosis. Compared with women with low PBB exposure (or=4 ppb) (HR = 0.90; 95% CI, 0.51-1.59) exposure did not have increased incidence of endometriosis. Increased incidence of endometriosis was suggested among women exposed to moderate PCB (5-8 ppb) (HR = 1.67; 95% CI, 0.91-3.10) and high PCB (>or=8 ppb) (HR = 1.68; 95% CI, 0.95-2.98) levels compared with low PCB exposure (