A large nationwide study suggests antibiotic use before conception and in early pregnancy is associated with higher risk of psychological distress in early to mid-pregnancy, with a stepwise increase as exposure spans more periods.

The findings reinforce prudent antibiotic prescribing, highlighting that antibiotics remain essential when medically necessary, but reducing unnecessary use may protect gut microbiota and potentially mental health without compromising infection management.

No competing interests were reported in connection with the JECS-based analysis.

The analysis involved about 94,490 pregnancies in JECS to examine whether antibiotic use around conception and early pregnancy is linked to distress measured in early to mid-pregnancy.

The report calls for future research to refine by antibiotic class, dosage, duration, and direct microbiome profiling to better understand causal pathways and potential interventions during pregnancy.

A proposed mechanism centers on gut microbiota disruption from antibiotics and the microbiota–gut–brain axis, though antibiotics should not be avoided when medically necessary.

Specific figures indicate that the odds of moderate distress were 1.12 and 1.22, and severe distress 1.07 and 1.50, for antibiotic use in one period and both periods respectively, after adjusting for key maternal factors.

Researchers emphasize that clinical practice and public health policy should balance effective infection treatment with awareness among women planning pregnancy or in early pregnancy about minimizing unnecessary prescriptions.

Practical guidance is provided, including that stopping antibiotics during pregnancy isn’t advised when medically necessary, and coverage of the gut-brain mechanism and the potential for microbiome recovery in early to mid-pregnancy.

The study, published in BMC Public Health in January 2026, used data from the Japan Environment and Children's Study (JECS) and was conducted by Matsumura and collaborators, with JECS funded by the Japanese Ministry of the Environment.

Adjusted models showed higher odds of moderate and severe distress for antibiotic use in one period and in both periods, compared with no antibiotic use.

Authors note that gut flora alterations have been linked to various health and psychiatric conditions, underscoring the importance of prudent prescribing.