Effects of timing of umbilical cord clamping on preventing early infancy anemia in low-risk Japanese term infants with planned breastfeeding: a randomized controlled trial

Abstract Background Japanese infants have relatively higher risk of anemia and neonatal jaundice. This study aimed to assess the effects of delayed cord clamping (DCC) on the incidence of anemia during early infancy in low-risk Japanese term infants with planned exclusive breastfeeding for 4 months. This study also aimed to explore the effects of DCC on neonatal jaundice. Methods We conducted an open-label, parallel-arm, multicenter randomized controlled trial of DCC (clamping the cord after more than a minute or pulsation stops) vs. early cord clamping (ECC; clamping the cord within 15 s) at one birth center and two clinics in Japan. Low-risk pregnant women planning to have a vaginal birth and to exclusively breastfeed and term singleton infants delivered in cephalic presentation were included in this study. The primary outcome was spectrophotometric estimation of hemoglobin at 4 months. Secondary outcomes were anemia incidence at 4 months, four outcomes related to neonatal jaundice, hematocrit levels, and related outcomes. Results Overall, 150 pregnant women were recruited. Participants (N = 138) were randomly allocated to two groups (DCC n = 68, ECC n = 70). There were no significant differences between the two groups in spectrophotometric estimation of hemoglobin at 4 months: mean difference = 0.1 g/dL, 95% confidence interval − 0.14, 0.35, DCC 12.4 g/dL, ECC 12.3 g/dL. Only the hematocrit levels on days 3 to 5 were significantly higher in the DCC group than in the ECC group: DCC 57.0%, ECC 52.6%, mean difference = 4.4, 95% confidence interval 2.61, 6.20. There were no significant differences in other secondary outcomes, including outcomes related to neonatal jaundice. Conclusion Among low-risk Japanese term infants with planned exclusive breastfeeding, DCC showed no significant effects on spectrophotometric hemoglobin levels at 4 months compared with ECC. We observed significantly higher hematocrit levels on days 3 to 5 in infants who underwent DCC, while these levels were within the normal range. Jaundice outcomes remained similar to those of infants who underwent ECC. Although a larger sample size is required to assess the effects of cord clamping on neonatal jaundice, DCC may prevent anemia in newborn infants. Trial registration UMIN-CTR; UMIN000022573, 06/01/2016 - retrospectively registered, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000023056