Inadvertent antibiotic exposure during pregnancy may increase the risk for neural tube defects in offspring

Background As emerging environmental contaminants, antibiotics pose potential threats to human health, in particular to pregnant women and infants. However, the potential harm of inadvertent antibiotic exposure (IAE) is often disregarded in light of the focus on intentional antibiotic use during pregnancy. Currently, little is known about the effects of IAE during pregnancy on fetal neural tube development. Methods In this case-control study, we used questionnaire data from 855 subjects to investigate the effects of intentional antibiotic use in early pregnancy on neural tube defects (NTDs). Then we tested for placental antibiotics in mothers who had not intentionally used antibiotics, and the compounds were detected in 379 subjects; these were considered IAE cases. We assessed the association between IAE during pregnancy and fetal NTDs using both multivariable logistic and multi-pollutant exposure models. We also analyzed the correlation between maternal dietary habits and placental antibiotics to explore possible sources of IAE. Results Only 50 of 855 participants (5.8%) intentionally used antibiotics and such use showed no significant association with NTD risk (odds ratio [OR] = 1.92, confidence interval [95%CI] = [0.66, 5.59]). However, 14 of 15 placental antibiotics were detected in 378 of 379 subjects (99.7%) and multivariable logistic analysis indicated that high levels of placental macrolides were significantly associated with increased NTD risk (4.42 [2.01–10.45]). Multi-pollutant exposure analysis suggested an increase in NTD risk with an increase in exposure to a mixture of placental antibiotics, among which macrolides were the most important contributor. In addition, the level of placental macrolides was positively correlated with the intake frequency of milk. Finally, mothers who drank river, well, or pond water had higher levels of placental macrolides than those who drank only tap water. Conclusions Intentional antibiotic use during early pregnancy may not be associated with NTDs, while IAE during pregnancy is associated with higher NTD risk in offspring. Macrolides are crucial risk factors. Milk, and river, well, or pond water may be important sources of IAE.