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Babies born even only a week or two before their due date may look perfectly healthy, but in reality, many face a far higher risk for medical problems than full-term babies, a study of thousands of births in Erie County has found.

Buffalo researchers also concluded that birth by cesarean section – the most common major operating room procedure performed in the United States – also increases the risks.

The study, published online Monday in JAMA Pediatrics, a pediatric journal, indicates that every week matters in the development of a baby prior to a normal birth.

About 4 million babies are born each year in the United States. The early-term deliveries that look normal – but often are not – account for 27.6 percent of births, or more than 1.1 million of the newborns.

“These babies can look big and healthy at delivery, so it’s important that you keep an eye on them and act promptly in case of any sign of trouble,” said Dr. Satyan Lakshminrusimha, an associate professor of pediatrics at the University at Buffalo and chief of the division of neonatology at Women & Children’s Hospital.

Lakshminrusimha, the study’s senior author, said early-term babies usually appear healthy and perform normally on Apgar tests used immediately after birth to evaluate a baby’s condition. As a result, he said, the newborns can give a false sense of assurance to parents and health care providers. The study, however, indicates a significant number of infants born at 37 weeks can experience low blood sugar, difficulty breathing and other problems within a few hours of delivery requiring admission to a neonatal intensive care unit.

Other studies have come to similar conclusions for so-called “late preterm” babies – those born at 34 to 37 weeks. The UB study arose from observations among neonatologists that babies born at 37 or 38 weeks experienced more health problems than those born at 39 to 41 weeks.

Birth by cesarean section significantly increased the chance of a babies experiencing these and other problems. Lakshminrusimha said the need for help with breathing increases for babies delivered by cesarean section because they do not experience all the hormonal changes during full-term labor, a process that clears fluid from newborns’ lungs.

Drs. William Oh of Women and Infants Hospital in Providence, R.I., and Tonse N.K. Raju of the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Md., said in an accompanying editorial that the findings reinforce the concept that maturation of babies is a continuum, and that any preset gestational age cannot be assumed to provide a clear separation between immaturity and maturity.

Because all immature infants carry risks, they said, physicians must carefully weigh the risks and benefits of immediate birth by cesarean section versus a full-term birth.

“Our results show the need for an increased awareness among health care providers that even though we consider babies born at 37 or 38 weeks almost term, they are still, to a large extent, physiologically immature,” said Dr. Shaon Sengupta, corresponding author of the study.

She launched the study as a UB medical resident in pediatrics and is currently on a neonatal-perinatal medicine fellowship at Children’s Hospital of Philadelphia. The research was funded by UB’s Division of Neonatology, UB’s Thomas F. Frawley MD Residency Research Fellowship Fund and an American Academy of Pediatrics Resident Research Grant.

email: hdavis@buffnews.com