Does vomiting and diarrhea during the second trimester of pregnancy affect the fetus?

In general, whether vomiting and diarrhea during the second trimester of pregnancy affect the fetus depends on the severity of symptoms. Mild and short-lived symptoms typically do not impact the fetus; however, if symptoms are severe and accompanied by dehydration or infection, adverse effects on the fetus may occur. The detailed analysis is as follows:

If the vomiting and diarrhea are mild—caused, for example, by improper diet or slight exposure to cold—and resolve quickly without leading to maternal dehydration or malnutrition, the oxygen and nutrients supplied to the fetus via the placenta remain unaffected, and adverse outcomes are unlikely.

However, if symptoms are severe, frequent vomiting and diarrhea can lead to maternal dehydration and electrolyte imbalances, which in turn impair blood flow through the placenta and reduce nutrient delivery to the fetus, potentially resulting in intrauterine growth restriction. If diarrhea is caused by bacterial or viral infections, pathogens may cross the placenta and affect the fetus, increasing the risk of complications.

During the second trimester, maintaining good dietary hygiene is essential. Avoid raw, cold, unclean, spicy, or irritating foods, keep the abdomen warm, and take preventive measures against vomiting and diarrhea. Once symptoms appear, promptly drink warm water or light salt water, follow a bland diet, shorten symptom duration, and minimize impacts on both mother and fetus.