The latest data on optimal timing of umbilical cord clamping, risks for maternal morbidity, and situations in which risks outweigh potential benefits.
During a discussion of labor management at her second-trimester visit, a 32-year-old woman asks about the benefits and risks of delayed umbilical cord clamping.
Q: What is delayed umbilical cord clamping?
A: Delayed umbilical cord clamping is prolongation of the time between delivery of a neonate and clamping of the umbilical cord. Immediate umbilical cord clamping is typically performed within 15 seconds of delivery, whereas delayed umbilical cord clamping is performed 25 seconds to 5 minutes after delivery.1 The procedure may increase the neonate’s blood volume by as much as 8% to 24% because continued blood flow through the fetal- placental unit facilitates placental transfusion to the neonate.2 In a way, delayed cord clamping can be seen as a return to a physiologic process, letting a natural process (transfusion of blood from placenta to baby) occur at birth, instead of iatrogenically interrupting it.
Recent studies have been performed to determine the risks and benefits of delayed umbilical cord clamping. Because physiology and morbidity differs widely between preterm and term neonates, these 2 groups have been investigated separately.
Q: What are the risks and benefits of delayed umbilical cord clamping in the preterm neonate?
A: Compared to term neonates, preterm neonates are at increased risk of temperature dysregulation, hypotension, and the need for immediate pediatric assessment and for blood transfusion. Multiple randomized controlled trials have compared these and other outcomes of immediate versus delayed cord clamping in preterm neonates.3-7
The data were recently summarized in a systematic review of 15 studies that included 738 neonates delivered between 24 weeks’ and 36 weeks’ gestation.8 The timing of delayed umbilical cord clamping ranged from 25 seconds to a maximum of 180 seconds after delivery; however, in the majority of the included randomized trials, the delay in umbilical cord clamping was 30–45 seconds.
Outcomes in both cesarean and vaginal deliveries were investigated. Overall, delayed umbilical cord clamping was associated with fewer transfusions for anemia, better circulatory stability, less intraventricular hemorrhage (all grades), and lower risk of necrotizing enterocolitis, but it was also associated with higher peak bilirubin concentrations (Table 1). There were no statistically significant differences in death, severe intraventricular hemorrhage (grades 3 or 4), or periventricular leukomalacia.
Data on long-term outcomes are not abundant. In one small study, no differences were found between immediate and delayed umbilical cord clamping when 58 survivors were evaluated with the Bayley II Scales of Infant Development at age 7 months.9 Therefore, while the immediate benefits of delayed umbilical cord clamping in preterm neonates are evident, the long-term effects are largely unknown.
In fact, some experts argue that additional trials are needed because of the relatively low number of early preterm neonates in existing RCTs and the lack of long-term follow up in the majority of existing trials.10
Additional data are expected from an ongoing large, international multicenter study evaluating delayed cord clamping in neonates <30 weeks’ gestation (Australian Placental Transfusion Study [APTS]; http://researchdata.ands.org.au/australian-placental-transfusion-study-apts).
Q: What are the risks and benefits of delayed umbilical cord clamping in the term neonate?
A: Compared to preterm neonates, term neonates (≥37 weeks’ gestation) have significantly lower risks of morbidity and mortality. Results of 15 randomized trials of delayed cord clamping in term neonates, including 3911 women, are summarized in a recent Cochrane Review.11 The systematic review found that delayed umbilical cord clamping was associated with higher neonatal hemoglobin concentration at 24 to 48 hours of life and lower likelihood of iron deficiency at 3–6 months, suggesting that an increase in iron stores persisted among neonates with delayed umbilical cord clamping. However, delayed umbilical cord clamping was also associated with an increased risk of jaundice requiring phototherapy.
In term neonates, therefore, the risk of jaundice must be weighed against the risk of iron deficiency. In developed nations where phototherapy is widely available, delayed umbilical cord clamping to increase iron stores has low potential for morbidity. As with data in preterm neonates, data also are lacking on long-term outcomes in term neonates with immediate versus delayed umbilical cord clamping.
In a recent RCT, the impact of positioning on outcomes of delayed cord clamping was assessed in term neonates following vaginal delivery. The researchers concluded that whether the neonate was held at the level of the vagina or placed on the maternal abdomen had no effect on the volume of placental transfusion.12
Q: Is there any risk to the mother with delayed umbilical cord clamping?
A: The maternal effects of delayed umbilical cord clamping have not been extensively studied. The theoretical risk is that delaying delivery of the placenta delays uterine contraction and increases blood loss. In cesarean deliveries, maternal blood loss also occurs through the hysterotomy incision, and delaying closure may lead to increased risk of hemorrhage. Five randomized trials of delayed umbilical cord clamping in term deliveries have investigated measures of maternal health.11 In a recent systemic review, rates of postpartum hemorrhage were not significantly increased. In addition, no differences were seen in mean blood loss, need for transfusion, postpartum hemoglobin concentration, or need for manual removal of the placenta. These results are encouraging, but it is important to note that they reflect data from only about 2000 pregnancies.11
Q: What about ‘milking’ or ‘stripping’ of the umbilical cord?
A: Milking and stripping of the umbilical cord are terms that apply to the active practice of squeezing blood down the cord to the baby. Typically, the delivering provider will “strip” a segment of the umbilical cord toward the fetal umbilicus 3–4 times before clamping the umbilical cord. Milking the umbilical cord is not physiologic and may provide a rapid bolus of blood to the infant; the aim is to shorten the time from delivery to clamping the umbilical cord while still providing up to 20 mL of placental blood.13 A limited number of studies have investigated the benefits of milking the umbilical cord in preterm and term neonates. No difference in outcomes was found in one small RCT performed in preterm neonates <33 weeks that compared umbilical cord milking to delayed umbilical cord clamping for 30 seconds.14
In a small study of umbilical cord milking versus immediate umbilical cord clamping in 24 term neonates, milking was associated with higher hematocrit levels at 36–48 hours of age.15
Overall, it is not yet clear whether milking or stripping the umbilical cord is equivalent to delayed cord clamping, and further study is necessary.
Q: What are the current recommendations from professional societies?
A: In 2012, the American College of Obstetricians and Gynecologists (ACOG) published a Committee Opinion on the timing of umbilical cord clamping after birth, which was also endorsed by the American Academy of Pediatrics.16
Current recommendations support delaying umbilical cord clamping in preterm neonates for 30–60 seconds after delivery with the neonate held at or below the level of the placenta. For term neonates, the ACOG Committee Opinion states that there is currently insufficient evidence to routinely recommend delayed umbilical cord clamping.
However, the World Health Organization recommends delaying umbilical cord clamping in term neonates for 1–3 minutes after birth while simultaneously initiating newborn care.17
Q: Under what circumstances should delayed umbilical cord clamping not be done?
A: Caution regarding delayed umbilical cord clamping is warranted in some situations. Most of the studies excluded neonates with congenital anomalies, as well as multiple gestations. In addition, among neonates with prenatal umbilical artery Doppler studies showing absent or reversed end diastolic flow, there is presumed to be no benefit to delayed umbilical cord clamping. Neonates whose well-being is of concern (eg, those with meconium-stained fluid or concerning fetal heart rate pattern), and particularly those with suspected severe depression (eg, with a very low or undetectable heart rate) should be immediately evaluated by pediatrics and resuscitated.
Placental abnormalities, such as placenta previa or accreta, vasa previa, and suspected placental abruption, are also potential contraindications to delayed umbilical cord clamping. Delaying further surgical management in these cases can lead to higher maternal morbidity. The risks and benefits of delayed umbilical cord clamping should be carefully considered in the setting of severe maternal anemia prior to delivery.
A summary of the state of the current science on delayed umbilical cord clamping is presented in Table 2.
Questions remain regarding optimal timing of umbilical cord clamping, risks for maternal morbidity, and situations in which risks outweigh potential benefits.
Current evidence suggesting neonatal benefits of delaying umbilical cord clamping in preterm neonates is strong, while there is more limited data demonstrating benefit in term neonates.
Dr. Conner is Fellow, Maternal-Fetal Medicine, Washington University, St Louis, Missouri.
Dr. Macones is Mitchell and Elaine Yanow Professor and Chairman of Obstetrics and Gynecology, Washington University, St. Louis, Missouri.
This opinion was developed by the Publications Committee of the Society for Maternal-Fetal Medicine with the assistance of Neil Silverman, MD, and was approved by the Executive Committee of the Society. Neither Dr. Conner, Dr. Macones, nor any member of the Publications Committee (see the list of 2014 members at www.smfm.org) has a conflict of interest to disclose with regard to the content of this article.
Disclaimer: The practice of medicine continues to evolve and individual circumstances will vary. Clinical practice also may vary. This opinion reflects information available at the time of acceptance for publication and is not designed nor intended to establish an exclusive standard of perinatal care. This publication is not expected to reflect the opinions of all members of the Society for Maternal-Fetal Medicine.
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2. Narenda A, Beckett C, Aitchison T, et al. Is it possible to promote placental transfusion at preterm delivery? Pediatr Res. 1998;44:453.
3. Aladangady N, McHugh S, Aitchison TC, Wardrop CAJ, Holland BM. Infants’ blood volume in a controlled trial of placental transfusion at preterm delivery. Pediatrics. 2006;117:93–99.
4. Baenzinger O, Stoklin F, Keel M, Siebenthal KV, et al. The influence of the timing of cord clamping on postnatal cerebral oxygenation in preterm neonates: a randomized, controlled trial. Pediatrics. 2007;119:455–460.
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6. Kugelman A, Borenstein-Levin L, Kessel A, Riskin A, Toubi E, Bader D. Immunologic and infectious consequences of immediate versus delayed umbilical cord clamping in premature infants: a prospective, randomized, controlled study. J Perinat Med. 2009;37:281–287.
7. Mercer JS, Vohr BR, McGrath MM, Padbury JF, Wallach M, Oh W. Delayed cord clamping in very preterm infants reduces the incidence of intraventricular hemorrhage and late-onset sepsis: a randomized, controlled trial. Pediatrics. 2006;117:1235–1242.
8. Rabe H, Diaz-Rossello JL, Duley L, Dowswell T. Effect of timing of umbilical cord clamping and other strategies to influence placental transfusion at preterm birth on maternal and infant outcomes. Cochrane Database Syst Rev. 2012;8:CD003248.
9. Mercer JS, Vohr BR, Erickson-Owns DA, Padbury JF, Oh W. Seven month developmental outcomes of very low birth weight infants enrolled in a randomized controlled trial of delayed versus immediate cord clamping. J Perinatol. 2010;30(1):11–16.
10. Tarnow-Mordi WO, Duley L, Field D, et al. Timing of cord clamping in very preterm infants: more evidence is needed. Am J Obstet Gynecol. 2014; doi:10.1016/j.ajog.2014.03.055.
11. McDonald SJ, Middleton P, Dowswell T, Morris PS. Effect of timing of umbilical cord clamping of term infants on maternal and neonatal outcomes. Cochrane Database Syst Rev. 2013;7:CD004074.
12. Vain NE, Satragno DS, Gorenstein AN, et al. Effect of gravity on volume of placental transfusion: a multicenter, randomized, non-inferiority trial. Lancet. 2014; doi:10.1016/S0140-6736(08)61345-8.
13. Brune T, Garritsen H, Witteler R, et al. Autologous placental blood transfusion for therapy of anemic neonates. Biology of the Neonate. 2002;81:236–243.
14. Rabe H, Jewison A, Alvarez RF, et al. Milking compared with delayed cord clamping to increase placental transfusion in preterm neonates: a randomized controlled trial. Obstet Gynecol. 2011;117:205–211.
15. Erickson-Owens DA, Mercer JS, Oh W. Umbilical cord milking in term infants delivered by cesarean section: a randomized controlled trial. J Perinatol. 2012;32(8):580–584.
16. ACOG Committee Opinion No. 543. Timing of umbilical cord clamping after birth. Obstet Gynecol. 2012;120(6):1522–1526.
17. World Health Organization. WHO Recommendations for the Prevention and Treatment of Postpartum Haemorrhage. Geneva:WHO, 2012.