Umbilical cord milking linked to high risk of brain bleeding in preterm infants
The term refers to gently squeezing the cord and pushing the contents into a newborn's abdomen before securing or clamping the cord and cutting it
Milking the umbilical cord -- which refers to gently squeezing the cord and pushing the contents into a newborn's abdomen before securing or clamping the cord and cutting it -- could increase the risk of severe brain bleeding in extremely preterm infants.
The World Health Organization (WHO) currently recommendsdelayed umbilical cord clamping (not earlier than 1 minute after birth) for improved maternal and infant health and nutrition outcomes.
In the study -- led by Dr. Anup Katheria from the Sharp Mary Birch Hospital for Women and Newborns in San Diego and colleagues at institutions in the US and Europe -- the researchers wanted to determine if cord milking was an alternative to delayed cord clamping.
However, the clinical trial, funded by the National Institutes of Health (NIH), was halted due to safety concerns for youngest preterm infants, that is, those who are born after 23 to 27 weeks of pregnancy.
"Although it's not possible to draw definitive conclusions, the results suggest extreme caution in performing cord milking in this vulnerable group of infants," says Dr. Caroline Signore, from NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, who oversaw the study.
In umbilical cord milking, blood is literally pushed into the fragile circulatory system of a premature infant. Unlike cord milking, a delay in clamping allows time for the blood to flow naturally from the cord into the abdomen before clamping and cutting the cord.
"Placental transfusion has become the accepted standard in newborn care with benefits to the neonate, including decreased mortality (death) in preterm infants and improved developmental outcomes in term infants. Umbilical cord milking has been endorsed as an alternative to delayed umbilical cord clamping, which is the current standard of care. Umbilical cord milking provides a placental transfusion by pushing blood toward the newborn before the umbilical cord is clamped with a duration similar to immediate umbilical cord clamping, allowing the neonatal team to begin resuscitation promptly," explains the study published in JAMA.
The initial plan was to enroll 1,500 infants, with 750 assigned at random to each group. Before the study was stopped, 474 infants were randomized, with 236 assigned to cord milking and 238 assigned to delayed clamping.
During the study, extremely preterm infants in the cord milking group were found to have more hemorrhages inside the ventricles, which is bleeding into the brain's fluid-filled cavities, as compared to the earliest preterm infants in the delayed clamping group. As a result of this, the study was stopped before enough infants could be enrolled to allow for a statistically valid analysis, say experts.
Since the higher risk of intraventricular hemorrhage was found only in extremely preterm infants, the team is continuing to compare cord milking to delayed clamping in preterm infants born at 30 to 32 weeks in a new trial. They will also evaluate the development of the two groups at two years of age.
"Because the increased rate of severe intraventricular hemorrhage appeared to be limited to infants born at 23 to 27 weeks' gestational age, the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the data and safety monitoring board approved a new trial of umbilical cord milking compared with delayed umbilical cord clamping in older gestational age infants (30-32 weeks' gestational age)," says the study.
What do previous studies say?
Some previous studies of term infants have found that delayed cord clamping reduces the chances of anemia and appears to benefit cognitive development in early childhood. In preterm infants, however, the extra time needed for delayed cord clamping may also delay the start of the "respiratory support often needed for the infants' underdeveloped lungs," say experts.
A previous research work -- which compared umbilical cord milking to delayed cord clamping in preterm infants delivered by cesarean -- had suggested that cord milking resulted in higher blood flow and benefits in cognitive development by two years of age.
"Umbilical cord milking compared with delayed umbilical cord clamping in a smaller randomized clinical trial was associated with higher cognitive and language scores at 22 to 26 months' corrected gestational age. Because of the importance of long-term neurodevelopment, all surviving infants will be followed up to determine developmental outcomes at 22 to 26 months' corrected gestational age," the team says in the study.
The authors of the current study say that they are unaware of any previous research that has demonstrated harm from umbilical cord milking.
Results from the clinical trial
For the current research work, the team enrolled women at less than 32 weeks of pregnancy at risk for preterm birth. When the women went into early labor, their infants were assigned at random to umbilical cord milking or delayed cord clamping for 60 seconds. For safety reasons, obstetricians could opt out of either procedure and immediately clamp the cord.
The research ethics committee or institutional review board at all nine participating sites -- six in the US and one site each in Ireland, Germany, and Canada -- approved this randomized clinical trial.
The results were categorized into a single combined outcome: death or severe intraventricular hemorrhage. Among the cord milking group, 29 infants (12%) died or developed severe intraventricular hemorrhaging, compared to 20 infants (8%) in the delayed clamping group, a difference that the researchers say was not statistically significant.
When the experts considered only the death rate, it also did not differ significantly between the two groups: 7% in the cord milking group versus 8% in the delayed clamping group. The analysis, however, shows that the rate of severe intraventricular hemorrhage was significantly higher in the cord milking group: 8% (20 infants), compared to 3% (8 infants) in the delayed clamping group.
Among those in the cord milking group, all 20 with intraventricular hemorrhage were the youngest preterm infants, born in weeks 23 to 27 of pregnancy, compared to 5 of the eight infants in the delayed clamping group.
"Among infants born at 28 to 32 weeks, no intraventricular hemorrhage occurred in the cord milking group, and three cases occurred in the delayed clamping group, a rate that did not differ significantly," says the study.
The researchers say that compared to more mature preterm infants, the circulatory systems of extremely preterm infants' have difficulty regulating blood flow in the brain. The researchers theorize that the increase in blood flow - resulting from cord milking - could have stressed the blood vessels in their brains, making them more likely to rupture.
"The pilot trial demonstrated that, compared with delayed umbilical cord clamping, umbilical cord milking at cesarean birth improved blood flow. However, improved blood flow in a very immature fragile brain may lead to an adverse outcome," the findings state.
In an editorial, experts say the "safest method for enhancing placental transfusion in preterm infants remains unclear" currently not only in terms of delayed cord clamping versus umbilical cord milking, but also in the duration of delay, the positioning of the infant with regard to the placenta, and the number of times the intact cord should be milked.
Till there are clearer results and well-defined standards, the experts recommend, that "in the meantime, clinicians should follow the WHO recommendation to delay cord clamping and cutting for 1 to 3 minutes for term infants and for at least 60 seconds for preterm infants to prevent iron deficiency and potentially enable more premature infants to survive."