The umbilical cord also termed as the navel string or funiculus umbilicalis, is the channel between the developing fetus and the placenta. It carries oxygenated blood and nutrients from the placenta to the fetus.
Now, a team of researchers at the Sharp Mary Birch Hospital for Women and Newborns in San Diego and other institutions warn against umbilical cord milking, squeezing the last drops of blood from the umbilical cord, previously believed in providing more nutrients to the baby.
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Milking the umbilical cord, which pushes the contents into the newborn’s abdomen before clamping the cord, could increase the risk for severe intraventricular hemorrhage, or bleeding into the brain’s fluid-filled cavities, in preterm infants born less than 32 weeks of gestation.
The researchers wanted to determine the difference in the rate for the composite outcome of mortality or severe intraventricular hemorrhage with umbilical cord milking versus delayed umbilical cord clamping. The study, which was published in the Journal of American Medical Association, shows that it’s dangerous for preterm infants who are subjected to umbilical cord milking. When the blood in the umbilical cord is forced into the baby’s abdomen, the pressure in the small vessels in the brain can rupture, leading to bleeding and can be potentially fatal for preterm infants.
Umbilical cord milking dangerous for preemies
The team enrolled 474 of a planned 1,500 infants born at less than 32 weeks of gestation. Infants were assigned to receive either placental transfusion with umbilical cord milking or delayed cord clamping.
The doctors studied preemies, those who were born between 23- and 27-weeks’ gestation. They had infants in groups – the delayed umbilical cord clamping and umbilical cord milking groups. They found that those preemies in the cord milking group had more hemorrhages inside the ventricles than those in the delayed clamping group.
In fact, the study, which was funded by the U.S. National Institute of Health, has been stopped immediately due to the increased risk of internal bleeding in the infants. Since the study was terminated early, the team weren’t able to perform the planned noninferiority analysis. Instead, they conducted a post-hoc comparison.
“Although it’s not possible to draw definitive conclusions, the results suggest extreme caution in performing cord milking in this vulnerable group of infants,” Dr Caroline Signore of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, said.
Further findings of the study show the primary outcome of death or severe intraventricular hemorrhage did not differ significantly for the umbilical cord-milking group compared to the delayed cord clamping group. But in the milking group, there is an increased rate of severe intraventricular hemorrhage or bleeding by 8 percent.
Delayed cord clamping benefits
In a previous study, umbilical cord milking compared to delayed cord clamping in preterm infants delivered via cesarean section had higher blood flow and better cognitive development. In another study in the 1940s show that preterm babies who had cord milking had lower risk of bleeding into the ventricles and had more blood volume. The researchers had no idea or any information of harm caused by umbilical cord milking; hence, the results of the current study surprised them.
In the present study, the researchers found that this practice can endanger the health of preterm infants. Compared to more mature preterm infants, the circulatory system of those who are extremely preterm is not yet fully functional, leading to difficulty in regulating blood flow to the brain.
The team suggest that the sudden increase in blood flow from cord milking may have imposed stress on the blood vessels in the brain, increasing the risk of blood vessel rupture. Since the complication is seen mostly in extremely preterm infants, the researchers plan to continue the study in preterm infants born between 30 and 32 weeks. They also plan to evaluate the development of infants in both groups at two years of age.
Purisch SE, Ananth CV, Arditi B, et al. Effect of Delayed vs Immediate Umbilical Cord Clamping on Maternal Blood Loss in Term Cesarean Delivery: A Randomized Clinical Trial. JAMA. 2019;322(19):1869–1876. doi: https://doi.org/10.1001/jama.2019.15995