Pregnant women who used antibiotics before or during early pregnancy were more likely to experience psychological distress than those who did not, according to a peer-reviewed study published in BMC Public Health.
The findings come from an analysis of 94,490 pregnant women enrolled in the Japan Environment and Children's Study (JECS), a nationwide birth cohort study tracking how environmental factors affect child health and development. Most participants enrolled at around 12 weeks of pregnancy, with follow-up assessments conducted at approximately 15 weeks.
Researchers tracked antibiotic use across two periods: from before conception until pregnancy recognition, and from pregnancy recognition until study enrollment. Participants were grouped into three categories — no antibiotic use, use during one of the two periods, and use during both periods. Psychological distress was measured using the Kessler Psychological Distress Scale (K6), a six-item self-reported questionnaire.
The analysis showed a stepwise pattern: the more periods during which a participant used antibiotics, the higher her likelihood of psychological distress. After adjusting for factors including maternal age, pre-pregnancy body mass index, education level, income, smoking status, alcohol use, marital status, and psychiatric history, the adjusted odds ratios for moderate psychological distress — defined as a K6 score of five to 12 — were 1.12 for use during one period and 1.22 for use during both periods. For severe psychological distress, with a K6 score above 13, the adjusted odds ratios were 1.07 and 1.50, respectively.
"We found that antibiotic use before and during pregnancy was associated with psychological distress in early- to mid-pregnancy, and that this association showed a stepwise pattern in a nationwide dataset of approximately 94,000 participants," said Kenta Matsumura, a public health researcher at the University of Toyama and lead author of the study.
One proposed mechanism involves the gut microbiome. Antibiotics are known to alter gut microbial composition, and disruptions to the gut microbiome have been associated with a range of conditions including obesity, diabetes, inflammation, and certain psychiatric conditions. The researchers note that this pathway warrants further investigation.
Perinatal depression — which encompasses depression occurring during pregnancy and in the postpartum period — is among the most common mental health conditions experienced by women, and is known to affect both maternal well-being and child development. The new findings add to a growing body of evidence suggesting that antibiotic exposure may be a contributing factor to maternal psychological distress, though the study's observational design means causation cannot be established.
The researchers were careful to emphasize that the findings should not discourage antibiotic use when medically indicated. "Antibiotics are essential when medically necessary; however, increasing awareness about avoiding unnecessary prescriptions — such as for common colds — may also be relevant from a maternal mental health perspective," Matsumura said.
