Figure and Figure showed the distributions of BPA levels respectively in the 97 maternal blood samples and the 97 fetal umbilical cord blood samples. A log normal distribution was used to fit both the maternal and fetal BPA concentrations, which display high fitness (r2 = 0.99). Maternal BPA concentrations were highly variable (ranging from 0.3 to 29.4 ng/ml), whereas most fetal BPA levels were < 1 ng/ml (77% of the samples were 0.3 ng/ml). The geometric means (GM) of maternal and fetal BPA levels were 2.5 ng/ml and 0.5 ng/ml, respectively. The GM of maternal BPA levels was five-fold higher than the fetal umbilical cord blood.
Distribution of BPA concentrations in (A) maternal blood samples and (B) fetal umbilical cord blood.
Table presented demographic characteristics, BPA levels, and lipid profiles of the 97 pregnant women and their newborns who participated in this study. The average (± S.D.) age, height, weight and BMI of pregnant women were 28.8 ± 3.7 years, 160.9 ± 5.2 cm, 65.3 ± 11.2 kg, and 25.2 ± 4.0 kg/m2. The average values for serum BPA, adiponectin and leptin were 5.4 ± 6.3 ng/ml, 6.6 ± 4.7 μg/ml, and 17.9 ± 13.9 ng/ml in pregnant women, and 1.1 ± 2.2 ng/ml, 21.3 ± 8.2 μg/ml, and 4.6 ± 3.5 ng/ml in neonates. The neonates average weight and gestational age were 3109.6 ± 319.0 g and 38.9 ± 1.1 weeks, respectively. Gender distribution among neonates was 57.7% male and 42.3% female.
Baseline anthropometric, metabolic characteristics and levels of adipokines corresponding to BPA level in study subjects
Based on the GM of maternal BPA levels, study subjects were divided into high- and low-BPA groups. The levels of TC and LDL were significantly higher in the low-BPA group than in the high-BPA group. Additionally, no significant differences in TRG, HDL, adiponectin and leptin levels were observed between these two groups. Neonates in the high BPA group were found to have lower birth weights than those in the low BPA group (p = 0.13). Some relevant differences between these two BPA groups were related to the gender of the infants.
To examine whether BPA exposure in pregnant women affected fetal BPA exposure and adverse outcomes, we analyzed the correlation between maternal BPA level, lipid profile, adipokines, birth weight, and gestational age (Table ). The maternal BPA levels showed a significantly inverse relationship to BMI (r = -0.48, at 3rd tertile BPA level), TC (r = -0.67, at 2nd tertile BPA level), and LDL (r = -0.61, at 2nd tertile BPA level), but were positively associated with TRG (r = 0.44, at 1st tertile BPA level). Moreover, the level of leptin displayed a significant correlation coefficient with increased BPA levels (r = 0.39 at 1st tertile, r = 0.50 at 2nd tertile, and r = 0.59 at 3rd tertile BPA level). Conversely, maternal BPA exposure had a significant negative association with neonatal BPA level (r = -0.53 at 3rd tertile BPA level) and birth weight (r = -0.24 at total sample and r = -0.39 at 3rd tertile BPA level).
Correlation between serum BPA levels and characteristics of pregnant women and healthy neonates
As shown in Table , the crude ORs showed that maternal BPA exposure was associated with LBW (OR 2.65, 95% CI 1.43-3.47) and SGA (OR 1.93, 95% CI 1.44-2.56) for male neonates but was not significantly associated with fetal adiponectin and leptin. Further adjustment for BMI, TC, TRG, HDL, LDL and adipokines attenuated this association, but maternal BPA exposure was still significantly related to an increased risk of fetal LBW (OR 2.12, 95% CI 1.05-2.38) and SGA (OR 1.34, 95% CI 1.13-2.83) in males. Additionally, the ORs of fetal adverse outcomes and the maternal BPA level were not observed in female neonates.
Odds ratio of BPA level contributed to low birth weight, small for gestation age, high leptin level, and low adiponectin level in neonates
The risks of fetal LBW, SGA, LAD, and HLP were plotted by quartiles based on maternal BPA exposure levels in Figure . Among male infants, the multivariable adjusted ORs of LBW of the second (OR 2.75, 95% CI 1.52-4.22) and fourth quartile (OR 2.42, 95% CI 1.72-3.36) of maternal BPA exposure, in contrast to the first quartile of BPA levels, showed that maternal BPA levels were significantly associated with an increased risk of LBW. The adjusted ORs of SGA of the second (OR 0.24, 95% CI 0.17-0.32) and the third quartile (OR 0.44, 95% CI 0.20-0.53) of maternal BPA level were significantly decreased, but increased in the fourth quartile (OR 2.01, 95% CI 0.99-0.62) (Figure ). The dose- response curve at SGA in male infants illustrated a U-shaped curve, but showed adverse effects at the highest BPA exposure (4th quartile). Additionally, significantly increased risks of LAD (OR 1.67, 95% CI 1.12-2.25) and HLP (OR 3.03, 95% CI 2.09-4.54) were observed for male neonates at the highest BPA exposure quartile (Figure ). In female neonates, BPA levels in the second (OR 2.99, 95% CI 1.47-4.11) and the fourth quartile (OR 2.17, 95% CI 1.19-3.12) were positively correlated with an increased risk of SGA presenting a Z-shaped curve and adverse effects (Figure ). Otherwise, the ORs of LAD were significantly decreased in the second (OR 0.21, 95% CI 0.10-0.21) and the fourth exposure quartiles (OR 0.55, 95% CI 0.34-0.56). The ORs of HLP at the second (OR 0.18, 95% CI 0.12-0.18) and third quartile (OR 0.11, 95% CI 0.06-0.11) of maternal BPA exposure were significantly decreased, but increased in the fourth quartile (OR 1.75, 95% CI 1.04-1.85) (Figure ). The dose-response curve of HLP in female infants showed a U-shape, but adverse effects were observed at the highest exposure quartile of BPA.
Adjusted ORs (95% CIs) of LBW, SGA, HAD and LAP by maternal BPA exposure quartiles. *Statistical significance at 5%.