Newborns with later clamping had higher hemoglobin levels 24 to 48 hours postpartum and were less likely to be iron-deficient three to six months after birth, the study determined.
In most hospital delivery rooms, doctors routinely clamp and sever the umbilical cord less than a minute after an infant’s birth, a practice thought to reduce the risk of maternal hemorrhaging.
But a new analysis has found that delaying clamping for at least a minute after birth, which allows more time for blood to move from the placenta, significantly improves iron stores and hemoglobin levels in newborns and does not increase the risks to mothers.
Doctors usually clamp the umbilical cord in two locations, near the infant’s navel and then farther along the cord, then cut it between the clamps. The timing of the procedure has been controversial for years, and the new analysis adds to a substantial body of evidence suggesting that clamping often occurs too quickly after delivery.
The new paper, published on Wednesday in The Cochrane Database of Systematic Reviews, may change minds, though perhaps not immediately. “I suspect we’ll have more and more delayed cord clamping,” said Dr. Jeffrey Ecker, the chair of committee on obstetrics practice for the American College of Obstetricians and Gynecologists.
Newborns with later clamping had higher hemoglobin levels 24 to 48 hours postpartum and were less likely to be iron-deficient three to six months after birth, compared with term babies who had early cord clamping, the analysis found. Birth weight also was significantly higher on average in the late clamping group, in part because babies received more blood from their mothers.
Delayed clamping did not increase the risk of severe postpartum hemorrhage, blood loss or reduced hemoglobin levels in mothers, the analysis found.
“It’s a persuasive finding,” said Dr. Ecker. “It’s tough not to think that delayed cord clamping, including better iron stores and more hemoglobin, is a good thing.”
The World Health Organization recommends clamping of the cord after one to three minutes because it “improves the iron status of the infant.” Occasionally delayed clamping can lead to jaundice in infants, caused by liver trouble or an excessive loss of red blood cells, and so the W.H.O. advises that access to therapy for jaundice be taken into consideration.
By contrast, in December a committee opinion by the American College of Obstetricians and Gynecologists reviewed much of the same evidence as the new analysis but found it “insufficient to confirm or refute the potential for benefits from delayed umbilical cord clamping in term infants, especially in settings with rich resources.”
The committee cited the risks of jaundice and the relative infrequency of iron deficiency in the United States as reasons for not changing longstanding practice.
But Dr. Tonse Raju, a neonatologist and an author of the guidelines, said he personally favored delayed cord clamping, even more so after this “very strong paper.”
The new report assessed data from 15 randomized trials involving 3,911 women and infant pairs. Eileen Hutton, a midwife who teaches obstetrics at McMaster University in Ontario and published a systematic review on cord clamping, called the report “comprehensive and well done” but said she felt the conclusion was “weakly worded,” considering the sum of evidence on the benefits of delayed cord clamping for neonates.
“The implications are huge,” Dr. Hutton said. “We are talking about depriving babies of 30 to 40 percent of their blood at birth — and just because we’ve learned a practice that’s bad.”
Said Dr. Raju, a medical officer at the National Institute of Child Health and Human Development: “It’s a good chunk of blood the baby is going to get, if you wait a minute and a half or two minutes. They need that extra amount of blood to fill the lungs.” Healthy babies manage to compensate if they do not get the blood from the cord, he said, but researchers do not know how.
American doctors hesitate to recommend delaying cord clamping universally, Dr. Raju said, because there can be situations in which early clamping is required — if an infant requires resuscitation, for example, or aspirates meconium, or infant stool.
The new analysis also found a 2 percent increase in jaundice among babies who got delayed cord clamping, compared with those who did not. Dr. Raju noted that the risk, although slight, increases the need for follow-up testing three to five days postpartum.
Susan McDonald, the lead author of the Cochrane review and a professor of midwifery at La Trobe University in Melbourne, Australia, said, “In terms of a healthy start for a baby, one thing we can do by delaying cord clamping is boost their iron stores for a little bit longer.”
The new analysis did not include many women who had Caesarean sections, some experts noted.
“We don’t have enough information on the effects of delayed cord clamping for someone undergoing a Caesarean delivery in terms of postpartum hemorrhage,” said Dr. Cynthia Gyamfi-Bannerman, medical director of the perinatal clinic at Columbia University. “Waiting 30 or 60 seconds in a vaginal delivery in a low-risk patient is probably something we could do and wouldn’t have maternal consequences, but in a caesarean delivery, you’re cutting into a pregnant uterus that has a huge amount of blood.” In some scenarios, “there’s an increased risk of postpartum hemorrhage.”
Dr. McDonald acknowledged that the review did not include data on the long-term neurological outcomes for babies.
“What will sway A.C.O.G. are a couple of studies in progress showing a potential long-term neurological benefit,” Dr. Raju said. Improved iron stores in theory could help reduce the risk of learning deficiencies and cognitive delay in children, which have been linked to iron-deficiency anemia in school-age children.