Intrauterine inflammation (IUI) is the inflammation of the chorion, amnion, and placenta. IUI is used interchangeably, considering that inflammation commonly affects the amniotic fluid, fetus, umbilical cord, or placenta, and fetal membranes, or decidua. 1-3 IUI is responsible for 40%-70% of pregnancies ending in preterm delivery because of preterm labor or preterm premature rupture of membrane (PPROM). 4 Untreated inflammation increases the risk of fetal inflammatory response syndrome (FIRS), which may result in multiorgan diseases, including the brain, cardiovascular system, lung, eye, and intestine. 5 Therefore, controlling inflammation in pregnant women is critical for reducing the risk of fetus developing these diseases. However, there are no safe and effective prenatal anti-inflammatory drugs that can be taken by pregnant women for all terms of pregnancy. Even the most widely used nonsteroidal antiinflammatory drugs (NSAIDs) can cause constriction of the ductus arteriosus, renal dysfunction, and hemostatic abnormalities in the

Intrauterine inflammation is defined as the inflammation of the chorion, amnion, and placenta. Untreated inflammation increases the risk of fetal inflammatory response syndrome, which may result in multiorgan diseases involving the brain, cardiovascular system, lung, eye, and intestine. Therefore, controlling inflammation is critical in pregnant women to reduce the risk of diseases. However, there are no safe and effective anti-inflammatory drugs for administration during pregnancy. Although the primary function of melatonin is to control circadian rhythms, it has protective effects against cellular insults occurring from hypoxia, oxidative stress, and inflammation. While animal studies support the effective and safe role of melatonin in improving pregnancy-related morbidities, it leaves plenty of opportunities for clinical studies investigating its anti-inflammatory, antioxidant, and protective effects against insults induced by intrauterine inflammation. Therefore, it will be worthwhile to investigate antenatal supplementation of melatonin in pregnant women with intrauterine inflammation to reduce the incidence of associated comorbidities.