In this study, we evaluated maternal and neonatal outcomes following DCC versus immediate cord clamping (ICC) in twin pregnancies. Our study demonstrated that DCC in twin pregnancy did not result in increased maternal postpartum blood loss, although it was associated with significantly higher neonatal hemoglobin levels, lower neonatal blood transfusion rate, and reduced risk of RDS compared with ICC.
Although DCC is known to be more beneficial for neonates than traditional ICC, DCC might also have potential risks of maternal or neonatal adverse effects such as increased maternal blood loss, neonatal polycythemia, hyperbilirubinemia, and jaundice1,11,17,18. As for maternal bleeding complications, theoretically, DCC might potentially cause more maternal blood loss at the uterine incision site or episiotomy site. In particular, DCC might result in greater maternal blood loss in twin pregnancies because DCC takes even longer time from delivery to incision site repair than single pregnancies.
In previous studies of singleton pregnancies, DCC did not increase the risk of maternal bleeding complications such as increased estimated blood loss, higher postpartum hemorrhage rate, higher maternal blood transfusion rate, lower postpartum hemoglobin levels, or greater mean hemoglobin changes1,2. In a randomized controlled trial of multiple-birth infants born preterm at 28‒36 weeks of gestation, rate of postpartum hemorrhage (defined as an estimated blood loss of > 500 ml for vaginal delivery or > 1,000 mL for cesarean delivery) was significantly higher in the DCC group than the ICC group (6/24 [25%] in DCC vs. 1/23 [4.3%] in ICC; P = 0.04)7. However, the sample size of that study was too small (24 and 23 mothers in DCC and ICC groups, respectively), with triplet pregnancies (7/47) included in that study. In a retrospective cohort study including 449 multiple pregnancies, there were no significant differences in maternal bleeding complications (including postpartum hemorrhage, estimated blood loss, maternal blood transfusions, therapeutic hysterectomy) between DCC and ICC groups13. That study was similar to our study because the sample size was large, the rate of higher-order pregnancies was relatively low (2/154 in DCC vs. 9/295 in ICC), and both preterm and full-term infants were included. In our study, postpartum hemoglobin levels tended to be slightly lower in the DCC group than in the ICC group, although such differences were not statistically different. In addition, the rate of postpartum hemoglobin drop ≥ 20% was slightly higher in the DCC group than in the ICC group. It was only statistically significant in the preterm delivery group. However, severe maternal postpartum hemorrhage leading to blood transfusion was not significantly different among all subgroups except the preterm delivery group. The reason for a higher rate of postpartum hemoglobin drop ≥ 20% in the preterm DCC group is not certain. It might be explained that most of the twin deliveries at preterm gestation are performed emergently and lower uterine segment is underdeveloped at preterm gestation which can result in more bleeding at the uterine incision site during cesarean section, especially when the uterine closure is delayed due to DCC. Another retrospective study of 82 twin pregnancies delivered at < 32 weeks of gestation showed that DCC was associated with higher estimated maternal blood loss in the cesarean section group, although maternal complications including maternal hemoglobin decrease, postpartum hemorrhage, blood transfusions, and hysterectomy were comparable between DCC and ICC groups6.
Previous studies have well demonstrated that DCC could increase neonatal hemoglobin levels, improve iron status, and reduce risk of neonatal morbidities in singleton pregnancies1,3,4,8. However, the effect of DCC on neonatal hemoglobin level in twin pregnancies was controversial in previous studies. A randomized controlled trial showed that neonatal hemoglobin levels were similar in preterm twins or triplets infants who received DCC (n = 51) or ICC (n = 50)7. A retrospective study of dichorionic twin pregnancies at 23‒32 weeks of gestation also reported that neonates who received DCC had no difference in neonatal hemoglobin level14. However, only 8 twin pregnancies (16 neonates) were included in the DCC group. In other studies, twins who received DCC had higher hemoglobin levels but lower rates of blood transfusion6,12,15,16. In our study, mean neonatal hemoglobin level was higher while neonatal blood transfusion rate was significantly lower in the DCC group than in the ICC group in all study population. In subgroup analyses, neonatal hemoglobin levels in all subgroups tended to be higher in the DCC group than in the ICC group. However, neonatal hemoglobin level was significant only in the cesarean section group. This was probably because the sample size of our study, especially the numbers of subjects in each subgroup, was too small. In our institute, we do not perform routine complete blood cell count test for healthy babies who are not admitted to the NICU. Thus, neonatal hemoglobin level data were available in only 151 (33.6%) of 450 in the DCC group and 433 (45.2%) of 962 in the ICC group. This is one of the main limitations of our study. However, neonatal blood transfusion data were available in all neonates. Its rate was significantly lower in the DCC group than in the ICC group, especially in twins delivered at preterm, twins delivered by cesarean section, and dichorionic twins.
Other benefits of DCC include reduced risk neonatal morbidities such as respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, and death or major disability1,3–5,16,19. However, most of these studies were done in singleton pregnancies. There are only a few studies on twin pregnancies6,7,12,14−16. A prospective cohort study of 202 twin pregnancies at > 32 weeks of gestation showed that twins who received DCC were at a lower risk of respiratory disorders and NICU admission16. Another retrospective cohort study including twin pregnancies at < 30 weeks of gestation showed a shorter NICU length of stay in DCC twins15. However, other studies of twin pregnancies found no differences in mechanical ventilator treatment, RDS, BPD, IVH, NEC, ROP, sepsis, death, or severe neurologic injury6,7,12,14. In our study, rates of NICU admission, mechanical ventilator treatment, RDS, BPD, NEC, and ROP were lower in the DCC group than in the ICC. Only the rate of RDS was significantly lower in the DCC group in the multivariable analysis. However, the sample size of our study as well as other previous studies might be insufficient to conclude effects on neonatal outcomes other than neonatal hematologic effects in twin pregnancies.
The strength of this study was that it had a relatively large sample size of 705 twin pregnant women (1,410 neonates) compared to previous twin studies. Another strength was that we recruited all twin pregnancies including both preterm and term gestation, both monochorionic and dichorionic twins, and both vaginal and cesarean delivery, while previous studies only included preterm twins or dichorionic twins. However, our sample size was still insufficient to have an adequate power because numbers of subjects in each subgroup were too low. In addition, neonatal hemoglobin level data were available in only less than half of all twin neonates. This study is further limited by the inherent nature of a retrospective study design. Maternal baseline characteristics and pregnancy outcomes were not comparable. Especially, more preterm twin pregnancies were included in the ICC group and cesarean section rate was higher in the ICC group. Although we performed subgroup analyses and multivariable analyses to control for bias, there might be other unknown potential confounding factors.