It’s well-established that infants born prematurely benefit from a delay in umbilical cord clamping. However, many preemies are born by cesarean section, and delayed cord clamping may be less effective and practical after surgical birth. Some obstetricians opt to speed things up by “milking” the umbilical cord, manually pushing blood from the placenta to the baby. A study published in Pediatrics this week shows that cord milking can be just as effective – if not more so – than waiting to cut the cord in premature babies born by C-section [full text PDF].1
In premature infants, delaying cord clamping for at least 30 seconds is associated with lower risk of intraventricular hemorrhage (IVH, bleeding in the brain), necrotizing enterocolitis (death of intestinal tissue), and anemia.2 Delayed cord clamping also benefits full-term babies, though the outcomes are less dramatic.3
Since 2012, ACOG has recommended a 30-60 second delay in umbilical cord clamping for preterm infants.4 However, they noted that little was known about the efficacy of delayed cord clamping after a C-section or about umbilical cord milking:
“More studies are needed to evaluate the potential benefits and risks of umbilical cord milking, and at this time there is insufficient evidence to support umbilical cord milking in preterm infants.”
“The ideal time for clamping the umbilical cord after cesarean delivery versus vaginal birth is an especially important area for future research. Premature infants, who may benefit most from delayed umbilical cord clamping, are more likely to be delivered by cesarean delivery because their mothers may have other medical and obstetric complications.”
These gaps in the research are definitely a challenge to implementing delayed cord clamping in premature infants. After a C-section, holding a wet, squirmy baby to delay cord clamping while mom’s uterus is still cut open is an awkward proposition. Research also shows that less transfusion occurs during delayed cord clamping in a C-section compared with a vaginal birth, perhaps because of fewer or weaker uterine contractions to expel the placenta.5 Plus, premature babies are more likely to need immediate medical attention, and while delayed cord clamping might be helpful to these babies, medical providers are understandably anxious to care for them. All of these factors can make delayed cord clamping more challenging and less effective in the babies that could most benefit from it.
For these reasons, the recent study of cord blood milking is a welcome addition to the research on this topic. The study was a randomized controlled trial conducted at two California hospitals. It included 197 preterm infants (<32 weeks), with 154 of these born by C-section. The infants were randomized to either have delayed cord clamping of 45-seconds or to have cord milking, with babies in both groups held at or ~20 cm below the level of the placenta. In the cord milking group, the obstetrician grasped the umbilical cord close to the placenta and slid his or her hand towards the baby to push the blood along through the cord. This was repeated four times, with a couple of seconds between each to allow the cord to refill with blood.
Among the babies born by C-section, the researchers found that several outcomes were better in the babies with cord milking compared with delayed cord clamping:
- Higher blood flow in the brain and heart (greater superior vena cava flow and right ventricular output) in the first 12 hours of life.
- Higher hemoglobin and blood pressure during the first 15 hours of life.
- Higher urine output in the first 24 hours of life.
These results indicate that cord milking transfers more blood to the baby than delayed cord clamping in preemies born by C-section. Greater blood flow might mean better protection against IVH. The incidence of IVH wasn’t different between the delayed cord clamping and cord milking groups in this study, but it wasn’t large enough to detect a difference.
In this study, 43 babies were born vaginally, and for them, cord milking didn’t improve outcomes over delayed cord clamping. It’s just in C-section births – and perhaps those where the baby needs immediate medical attention – that cord milking may be preferable.
I was interested in this study because cord milking has been a sort of gray area in the delayed cord clamping literature. It’s often offered as an alternative to delayed cord clamping, but as ACOG said in 2012, its safety and efficacy hadn’t been as well-studied. With this and other recent studies, that is changing. A meta-analysis published earlier this year in JAMA Pediatrics included 7 randomized controlled trials with a total of 501 babies. Among preterm babies, it found that cord milking improved hemoglobin and hematocrit, reduced the need for supplemental oxygen, and reduced the risk of IVH, all without adverse effects.6 With the addition of the current study, we have more evidence that cord milking works to improve placental transfusion, and in the specific case of preemies born by C-section, may even be preferable to delayed cord clamping.
I’ve been following the delayed cord clamping literature for some time now, and the evidence is now quite strong that babies, and especially preterm infants, benefit from receiving the blood in the umbilical cord and placenta after birth. More and more, this seems to be true whether the blood transfusion happens through patient waiting or with the help of cord milking.
- Katheria, A. C., Truong, G., Cousins, L., Oshiro, B. & Finer, N. N. Umbilical Cord Milking Versus Delayed Cord Clamping in Preterm Infants. Pediatrics peds.2015–0368 (2015). doi:10.1542/peds.2015-0368
- Rabe, H., Diaz-Rossello, J. L., 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. 8, (2012).
- McDonald, S. J. & Middleton, P. Effect of timing of umbilical cord clamping of term infants on maternal and neonatal outcomes. Cochrane Database Syst. Rev. 7, CD004074 (2013).
- ACOG Committee on Obstetric Practice. Committee Opinion No.543: Timing of Umbilical Cord Clamping After Birth. Obstet. Gynecol. 120, 1522–1526 (2012).
- Aladangady, N., McHugh, S., Aitchison, T. C., Wardrop, C. A. J. & Holland, B. M. Infants’ Blood Volume in a Controlled Trial of Placental Transfusion at Preterm Delivery. Pediatrics 117, 93–98 (2006).
- Al-Wassia, H. & Shah, P. S. Efficacy and safety of umbilical cord milking at birth: a systematic review and meta-analysis. JAMA Pediatr. 169, 18–25 (2015).