Oct 18 2004
Waiting 30 seconds to two minutes after birth to cut the umbilical cord of a premature baby appears to lessen chances of bleeding in the newborn’s brain and reduce the need for transfusions, according to a new review of research.
Standard practice for preterm babies is to cut the cord as soon as possible, often within 10 to 15 seconds.
A systematic review finds that delaying the clamping rather than doing it immediately also reduces anemia and increases blood pressure and blood volume, helping preterm infants off to a healthier start in life, says lead study author Heike Rabe, M.D., Ph.D. of Brighton and Sussex University Hospitals in Brighton, England.
“If the cord is left unclamped for a short time after the birth, some of the baby’s blood from the placenta passes to the baby to help the flow of blood to the baby’s lungs,” Rabe explains. “Delaying cord clamping for just a very short time helped the babies to adjust to their new surroundings better.”
The review appears in the October issue of the Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
Medical staff ordinarily clamp the umbilical cord in two places after the baby is delivered, then cut the cord between the two clamps.
“I’m comfortable with the 30-second delay, but there are so many things that can happen with a preterm infant that doctors have to use their judgment in each case,” says neonatologist Tonse N. K. Raju, M.D., D.C.H., of the National Institute of Child Health and Development in Bethesda, Md.
The seven studies in Rabe’s systematic review covered 297 infants. The studies measured blood pressure, red blood cell counts, blood volume, bleeding within the brain and the need for transfusions.
Since 60 percent to 80 percent of preterm infants less than 32 completed weeks’ gestation require transfusion, strategies that might reduce this without risk would be desirable, says Rabe. Decreasing the need for transfusion would be especially valuable in developing countries, where transfusion carries a high risk of transmitting infection.
No formal guidelines currently set the time for clamping the cord. The American College of Obstetricians and Gynecologists says it does not take a position on the timing of cord clamping, citing “insufficient evidence.”
However, pre-term infants (those born at 24 to 37 weeks) often have trouble breathing, so physicians prefer moving them immediately to intensive care units where they are helped to breathe. Moving the baby requires clamping and cutting the umbilical cord quickly.
“The acceptable range of red blood cell levels or blood pressure in preterm infants is so narrow that even seconds can make an important difference,” Raju says. Despite this importance, evidence is sparse.
“Clamping time is seen as so unimportant that it’s not even recorded on hospital charts, which makes it hard to do even retrospective studies,” says Judith Mercer, C.N.M., D.N.Sc., of the University of Rhode Island, who has studied the issue.
Despite concerns for the baby’s respiratory status, the trials covered in the review offered little guidance about how breathing is affected by cord clamping time, Rabe says. “At least there was no negative effect on babies’ breathing after delaying the clamping of the cord.”
Practices vary with who is delivering the baby and where, says Mercer. “In the United States, it’s more common to cut the cord immediately, while in Europe it’s more common to delay.”
Nurse-midwives favor delaying, compared to physicians, she says. They prefer clamping at between one and three minutes (35 percent) or even later (33 percent), she found after surveying 303 midwives.
Arguments exist for both early and delayed clamping. Clamping too soon prevents blood from returning through the umbilical cord to the baby’s body.
“A little extra blood can help restore blood pressure,” says Raju. Low blood pressure may require transfusions of blood or fluids, which can be tricky to accomplish safely in a preterm baby.
On the other hand, delaying clamping too long can actually pack too many red blood cells into the baby’s system. That can make the blood too thick, stressing the heart and respiration, and possibly triggering jaundice or brain damage. Such a delay may also prevent adequate resuscitation or unnecessarily expose the baby to cold.
Mercer notes that few long-term studies have examined what happens to these babies as they grow up.
She is conducting a randomized controlled trial funded by the National Institutes of Health of early versus later clamping times in 74 preterm babies. In this study, the infants will be followed until they are 7 months old when developmental testing will be done. Eventually, she hopes to track them up to age 5. Although the study is not complete, she says that the data safety checks show no harm from a delay of 30 to 45 seconds at birth.
While expectant mothers should not have to think about the details of cord-clamping time, physicians and midwives should familiarize themselves with the review’s conclusions, Raju says.
The Cochrane Collaboration has a systematic review of cord-clamping times in full-term infants in process and plans to publish it soon.
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