Abstract Objective To evaluate the effect of later cord clamping (LCC) on umbilical arterial blood gas in neonates of diabetic mothers. Methods This prospective study included a group of 160 diabetic mothers (DM) whose neonates were randomized to immediate cord clamping (ICC) (≤ 15 s after birth) or LCC (≥ 30 s after birth), and a group of 208 non-diabetic mothers (NDM) whose neonates were randomized to ICC or LCC as a reference. Cord arterial pH, base excess (BE), bicarbonate (HCO3−), partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2), lactate, hemoglobin, hematocrit and glucose were compared among groups. Results In neonates of DM, there was no significant difference in cord arterial pH between the ICC and LCC group. LCC of ≥ 30 s decreased umbilical arterial HCO3− and BE and increased lactate (ICC versus LCC, HCO3−: 24.3 (22.7, 25.8) versus 23.7 (22.3, 24.7) mmol/L, P = 0.01; BE: -2.70 (-4.80, -1.50) versus − 3.72 (-5.66, -2.36) mmol/L, P = 0.006; lactate: 2.1 (1.6, 3.7) versus 2.7 (2.1, 4.3) mmol/L, P = 0.005), without the alterations of pCO2, pO2, hemoglobin, hematocrit and glucose. Similar results were found in neonates of NDM (ICC versus LCC, HCO3−: 24.3 (23.1, 25.7) versus 23.5 (22.3, 24.8) mmol/L, P = 0.01; BE: -2.39 (-3.73, -1.51) versus − 3.40 (-4.73, -1.91) mmol/L, P = 0.001; lactate: 2.2 (1.9, 3.3) versus 2.5 (2.0, 4.3) mmol/L, P = 0.01), except for the higher level of hemoglobin in the LCC group. The majority of diabetic mothers (ICC: 92.0%; LCC: 91.8%) had good blood glucose control. No differences were observed in acid-base status and glucose between neonates of DM and neonates of NDM in both ICC and LCC, but hemoglobin and hematocrit were elevated after ICC in neonates of DM compared to neonates of NDM. Conclusions Later cord clamping of ≥ 30 s resulted in a tendency towards metabolic acidosis of umbilical arterial blood in neonates of DM and NDM. Umbilical arterial blood gas parameters at birth were similar in neonates of DM and NDM. Trial registration ClinicalTrials.gov: NCT04369313; date of registration: 30/04/2020 (retrospectively registered).

Background Delayed cord clamping in full-term neonates is widely recommended, while in practice, it is rarely implemented in cesarean section due to the fear of neonatal jaundice and excessive maternal blood loss. The optimal timing of cord clamping remains uncertain. This study was to fully evaluate the effects of delayed cord clamping on short-term hematological status and jaundice in term neonates delivered by cesarean section. Methods This retrospective study enrolled 796 women, who were allocated into the early cord clamping group ( n = 377) and the delayed cord clamping group ( n = 419). The latter group was further divided into two subgroups (30–60 s, 61–120 s). The outcomes were neonatal transcutaneous bilirubin levels on 0 to 5 days of life and the rate of phototherapy. For neonates who had blood tests on the first three days of life, their hemoglobin and hematocrit were compared among groups. Results Compared with the early cord clamping group, delayed cord clamping merely increased the transcutaneous bilirubin level of neonates on the day of birth rather than that on the following five days. The heel peripheral blood sample size of 1–3 days in the early cord clamping group was 61, 25 and 33, and in the delayed cord clamping group was 53, 46 and 32, respectively. Delayed cord clamping at 30–60 s resulted in the higher neonatal hemoglobin level on day 3 and an increased rate of neonatal polycythemia, without a higher rate of phototherapy. Delayed cord clamping beyond 60 s did not further improve hematological status in term neonates born by cesarean section. Conclusion In cesarean section, delayed cord clamping for 30–60 s improved the early hematological status of term neonates without the enhanced requirement of phototherapy for neonatal jaundice.