Perinatal Depression: Antibiotics Before Pregnancy May Affect The Mother's Mental Health

The study investigated the relationship between antibiotic use before pregnancy and psychological distress during gestation, using data from a large group of Japanese women. The results indicated that more frequent antibiotic use is associated with a higher risk of emotional distress, especially at more severe levels. These findings reinforce the importance of using antibiotics cautiously, especially in women planning to become pregnant, and highlight the need for more research on the effects of these medications on mental health.

Depression that occurs during pregnancy or after the birth of the baby, known as perinatal depression, is a very common and significant health problem. In higher-income countries, it is estimated that between ten and fifteen percent of women experience this condition.

This type of depression not only affects the mother's emotional well-being but can also interfere with the baby's development and family dynamics as a whole. In more severe cases, it is even associated with the risk of maternal suicide, making it an important public health issue. Therefore, understanding the factors that increase the risk of this condition is essential to prevent and reduce its impacts.

In recent years, researchers have sought to identify different causes for the onset of perinatal depression. It is known that it does not depend on a single factor, but rather on a combination of psychological, social, economic, and biological aspects. Among the most recent possible risk factors, the use of antibiotics has begun to attract attention.

These medications are widely used, including during pregnancy, and previous studies suggest they may be linked to changes in mental health, possibly increasing the risk of depression and anxiety.

One explanation for this relationship is related to the role of the bacteria that live in our gut, known as the gut microbiota.

Antibiotics can alter this natural balance, eliminating not only harmful bacteria but also beneficial ones. This alteration can affect bodily processes related to inflammation, metabolism, and even brain function, influencing mood and behavior.

Despite these hypotheses, there is still little clear evidence on how antibiotic use before pregnancy can impact the mental health of pregnant women.

Given this gap, the study in question aimed to investigate whether antibiotic use prior to pregnancy is associated with psychological distress during the first months of gestation. To this end, the researchers used data from a large study conducted in Japan, which follows pregnant women and their children over time. The idea was to observe patterns and possible relationships between the history of antibiotic use and the emotional state of the participants during pregnancy.

Regarding the methods, the study analyzed information from more than ninety thousand pregnant women, which lends considerable robustness to the results. The participants were part of a large national project that collects data on health, environment, and child development.

The researchers classified antibiotic use into three distinct groups: women who did not use antibiotics in the year prior to pregnancy, those who used them in only one of the periods evaluated (before or shortly after confirmation of pregnancy), and those who used them in both periods. This division allowed for the comparison of different levels of exposure to the medication.

To assess the emotional state of pregnant women, a well-known standardized scale in the field of mental health was used, which measures the level of psychological distress based on responses to questions about feelings such as sadness, anxiety, and emotional exhaustion. The scores obtained were divided into categories indicating moderate or severe distress.

Next, the researchers applied an advanced statistical model that allows them to analyze the probability of these levels of distress occurring, taking into account other factors that could also influence the results, such as age, socioeconomic status, and health history.

The results showed that women who used antibiotics in both periods evaluated were more likely to suffer from moderate and, especially, severe levels of psychological distress during pregnancy. Furthermore, a "dose-response" pattern was observed; that is, the greater the exposure to antibiotics, the greater the identified risk. This suggests that even relatively limited use of these medications may be associated with impacts on mental health.

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Periconceptional antibiotic use and early- to mid-pregnancy psychological distress in a nationwide birth cohort: cross-sectional analysis from the Japan Environment and Children’s Study

Kenta Matsumura, Hitomi Inano, Junko Sakai, Kanako Shimada, Akiko Tsuchida, Hidekuni Inadera, and the Japan Environment and Children’s Study (JECS) Group. 

BMC Public Health. Volume 26, article number 863, (2026).

DOI:10.1186/s12889-025-26119-0

Abstract:

Antibiotic use has recently emerged as a potential risk factor for psychiatric disorders, but evidence regarding its risk during pregnancy remains limited, despite the frequent use of antibiotics in pregnant women. We investigated the association between antibiotic use in the year prior to early pregnancy and psychological distress during early- to mid-pregnancy. Participants were 94,490 expectant mothers from the Japan Environment and Children’s Study, an ongoing nationwide birth cohort study. Antibiotic use during the year before early pregnancy was categorized as follows: (1) no use, (2) use during either the period before or after pregnancy recognition, and (3) use during both periods. Psychological distress was measured during early- to mid-pregnancy using the Kessler Psychological Distress Scale, with scores of 5–12 and ≥ 13 indicating moderate and severe psychological distress, respectively. A Bayesian multinomial generalized linear model was used to calculate adjusted odds ratios (aORs) and 95% credible intervals (95% CrIs), controlling for a priori selected potential confounders. Analysis using no antibiotic use as a reference revealed that the aORs (95% CrIs) for moderate psychological distress were 1.07 (0.97–1.19) for use during either period and 1.22 (1.08–1.38) for use during both periods. For severe psychological distress, the aORs (95% CrIs) were 1.07 (0.97–1.19) and 1.50 (1.15–1.94), respectively. A dose–response-like pattern was observed, suggesting that even limited antibiotic use may be an independent risk factor for psychological distress during early- to mid-pregnancy, highlighting the importance of judicious antibiotic use from the preconception period.