Babies born just a few weeks premature are six times as likely to die in the first week of life as newborns carried to term, according to a new study.
The research also reiterates that late preterm babies - born at 34 to 36 weeks gestation - have a broad range of medical complications, including breathing problems, trouble feeding, jaundice and slowed brain development.
"This study adds to our growing knowledge of the increased medical complications and higher risk of infant death among late preterm infants compared with babies born full term," Joann Petrini, director of the Perinatal Data Center at the March of Dimes in White Plains, N.Y., and co-author of the study, said in an interview.
"Babies born just a few weeks too soon should be closely monitored," she said.
A baby is considered full term if born between 37 and 41 weeks' gestation. Prematurity is defined as giving birth before 37 weeks. The new study, published in today's edition of the Journal of Pediatrics, notes that the number of premature births has risen sharply since the 1980s, and the death rate of babies has fallen.
The study is based on birth and infant death data collected in the United States from 1995 to 2002.
During that time period, there were 30.7 million singleton live births in the United States. (Multiple births, where prematurity is commonplace, were excluded.)
Dr. Petrini said that while much attention has focused on the so-called super-preemies who are born before 32 weeks, the reality is that three in four premature births occur in the 34- to 36-week range.
"We hope this new study will draw attention to this group, which has largely been ignored," she said.
Dr. Petrini said it is often assumed that late preterm babies will be fine, to the point where induction and cesarean delivery are common in this period.
"These decisions are very complicated and should not be taken lightly," she said. "We hope this new information will be one more element in solving the puzzle."
The study showed that infant mortality is infrequent, but it is significantly higher among late-term babies than full-term ones - 7.9 per 1,000 births, versus 2.4 per 1,000 in the first year of life.
During the first week after birth, the disparity was even more stark - 2.8 deaths per 1,000 births in late-term babies compared to 0.5 per 1,000 in full-term ones.
The leading causes of death in babies are congenital malformations, sudden infant death syndrome, unintentional injuries from falls and motor vehicle crashes, heart disease, birth asphyxia (a baby does not receive enough oxygen before, during or just after birth), influenza and homicide.
Dr. Petrini noted that the leading cause of death is congenital malformations and it is not clear that carrying a baby to term would change those outcomes. However, the new study showed that when babies with abnormalities were factored out, the death rate still remained markedly higher in late preterm babies.
There are about 330,000 lives births a year in Canada, and about 40,000 of those babies are born prematurely. About 1,700 babies die in Canada annually, the majority of them preemies.
The treatment of premature babies costs more than $2-billion annually in Canada, and about $26-billion south of the border, according to the March of Dimes.
The treatment costs of late preterm babies are about 10 times those of full-term babies.
