Extremely preterm infants are surviving in greater numbers

Extremely preterm infants, those born before the 28th week of pregnancy, are surviving in greater numbers and escaping serious illness, according to a comprehensive review of births in a National Institutes of Health research network.

The study, published in the Journal of the American Medical Association, reviewed the birth records of more than 35,000 premature infants born from 1993 to 2012 in 26 U.S. centers participating in the Neonatal Research Network, a program funded by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). The lead author was Barbara J. Stoll, M.D., chair of pediatrics at Emory University School of Medicine.

• Infants born at 23 and 24 weeks survived in greater numbers over the 20-year period. Of those born at 24 weeks, for example, only 52 percent survived in 1993 while 65 percent survived in 2012.
• A higher number of premature infants survived without major illnesses. For infants born at 27 weeks, for example, survival without major illness increased from 29 percent in 1993 to 47 percent in 2012.

Among the survivors, the researchers saw an increase in the rate of bronchopulmonary dysplasia a complication often resulting from respiratory therapy. Improvements in respiratory care appear to have saved many infants who otherwise may have died. Nonetheless, the infant's’ underdeveloped lungs often sustain damage.

“NICHD has funded newborn care research for many years,” said Rosemary Higgins, M.D., who oversees NICHD’s Neonatal Research Network. “We’re now seeing the results of that investment in improvements in survival and outcomes.”

More than 450,000 premature babies are born each year in the United States. Higgins attributed the boost in survival to advances in maternal and newborn care, such as the increased use of antenatal steroids - these drugs are given to women at risk for preterm birth to help stimulate lung development in the fetus. In 1993, physicians gave antenatal steroids to only 24 percent of women at risk for delivering too early, according to the study. A 1995 NIH consensus statement on antenatal steroids led to the widespread use of the treatment. By 2012, doctors were giving the steroids to nearly 87 percent of at-risk pregnant women.

The study authors noted that the increase in survival of extremely preterm infants parallels an increase in cesarean sections in this age group. It’s possible, Dr. Higgins explained, that “physicians are more likely to perform the surgery than they were in previous years.” The surgery may result in a less traumatic birth for the infant and therefore may contribute to survival.

The study authors also stressed the need for continued research on the care of extremely premature infants. Although survival has increased over the past two decades, including survival without major illnesses, preterm birth in the United States still poses a substantial burden to families and society at-large, they wrote.

Umbilical cord ‘milking’ improves blood flow in preterm infants

A technique to increase the flow of blood from the umbilical cord into the infant’s circulatory system improves blood pressure and red blood cell levels in preterm infants delivered by cesarean section, according to a study funded by the National Institutes of Health.

The study, published online in Pediatrics, was conducted by researchers at the Neonatal Research Institute at Sharp Mary Birch Hospital for Women and Newborns in San Diego, and Loma Linda University, Loma Linda, California. It was supported by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).

The technique, known as cord milking, consists of encircling the cord with thumb and forefingers, gently squeezing, and slowly pushing the blood through the cord to the infant’s abdomen. For infants delivered by cesarean, cord milking appears to offer benefits over the standard practice of waiting 45 to 60 seconds before clamping and then cutting the umbilical cord. These benefits, which include greater blood flow to and from the heart, higher red blood cell level, and higher blood pressure, were seen only in the infants delivered by cesarean. Among a smaller number of vaginal births, the researchers found no difference in blood volume between infants undergoing cord milking and those undergoing delayed cord clamping.

“The study results are very encouraging,” said Tonse Raju, M.D., chief of NICHD’s Pregnancy and Perinatology Branch. “The findings need to be confirmed in a larger number of births, but at this point, it appears that umbilical cord milking may prove to be of great benefit to preterm infants delivered via cesarean.”

Delaying umbilical cord clamping by 30 to 60 seconds is thought to allow sufficient time for blood from the umbilical cord to fill the blood vessels in the infant’s lungs, Dr. Raju explained in an earlier podcast. Among preterm infants, the delay is believed to protect from intraventricular hemorrhage, or bleeding in the ventricles — the cavities inside the infant’s brain. The hemorrhage is thought to result from low blood pressure, brought on by having too little blood in the circulatory system. Bleeding in the brain may result in developmental delays, cerebral palsy, and in severe cases, death.

However, Dr. Anup C. Katheria, M.D., a neonatologist at the Neonatal Research Institute at the Sharp Mary Birch Hospital and the study’s first author, noted that some studies failed to find a reduction in intraventricular hemorrhage from delayed cord clamping among preterm infants delivered by cesarean. The scientists theorized that the use of an anesthetic in cesarean delivery reduces uterine contractions, and in so doing hinders the exodus of blood from the umbilical cord. Cord milking, they reasoned, might compensate for diminished blood flow through the umbilical cord and increase the amount of blood available to the infant.

The researchers enrolled 197 infants in their study. Mothers went into labor at or before the 32nd week of pregnancy. Of these, 154 were delivered by cesarean, with 75 assigned at random to the umbilical cord milking group and 79 assigned to the delayed clamping group. The 43 infants delivered vaginally also were assigned at random to either delayed clamping or umbilical cord milking.

Of the infants undergoing cesarean deliveries, those in the cord milking group had higher blood flow in the superior vena cava, the large vein carrying blood from the brain to the heart, and a higher output of blood from the right ventricle. The two measures, taken together, are an indication of blood circulation in the brain and body. Infants in the cord milking group also had higher blood pressure and higher levels of hemoglobin—a protein used as an indicator of the quantity of red blood cells.

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