Under the COVID-19 (Coronavirus Disease 2019) pandemic, limitations are known to cause some psychosocial problems. We compared the results of mental screening of the postpartum women conducted during the COVID-19 epidemic with those at the same period last year. Based on the results, the worse mother-infant bonding was suspected at 1 month after birth under the COVID-19 pandemic.

We examined the effect of early skin-to-skin contact (SSC) on breast-feeding at 1 month after delivery, in Japanese women. We reviewed the obstetric records of healthy nulliparous women with vaginal singleton delivery at 37–41 weeks’ gestation, at the Japanese Red Cross Katsushika Maternity Hospital and between 1 February and 30 November 2011, there was a total of 403 women who planned to breast-feed their babies at birth. Of these, 272 women (67.5%) initiated early SSC in the delivery room and 131 women (32.5%) did not initiate early SSC. There were no significant differences in the obstetric characteristics and birth outcomes between the two groups of women with and without initiating early SSC. However, the rate of exclusive breast-feeding at 1 month after delivery in the group of women following early SSC (59.6%, 162/272) was significantly higher than that in the group of women without early SSC (45.8%, 60/131; crude OR 1.74, 95% CI 1.1–2.7, p = 0.009). The current results may support the benefit of early SSC in Japanese women after vaginal delivery.

Preterm birth (PB) is the most-frequent complication occurring during pregnancy, with a significant impact on neonatal morbidity and mortality. Chorioamnionitis (CAM), the neutrophil infiltration into chorioamniotic membranes, is a major cause of PB. However, several cases of PB have also been reported without apparent pathogenic infection or CAM. Such cases are now attributed to "sterile inflammation." The concept of sterile inflammation has already attracted attention in various diseases, like cardiovascular diseases, diabetes, and autoimmune diseases; recently been discussed for obstetric complications such as miscarriage, PB, gestational hypertension, and gestational diabetes. Sterile inflammation is induced by alarmins, such as high-mobility group box 1 (HMGB1), interleukins (IL-33 and IL-1α), and S100 proteins, that are released by cellular damage without apparent pathogenic infection. These antigens are recognized by pattern-recognition receptors, expressed mainly on antigen-presenting cells of decidua, placenta, amnion, and myometrium, which consequently trigger inflammation. In reproduction, these alarmins are associated with the development of various pregnancy complications, including PB. In this review, we have summarized the development of PB related to acute CAM, chronic CAM, and sterile inflammation as well as proposed a new mechanism for PB that involves innate immunity, acquired immunity, and sterile inflammation.