By JANE E. BRODY
The March of Dimes opened a new campaign this summer to curb the large and growing number of otherwise healthy pregnancies that are deliberately ended early by induced labor or Caesarean delivery.
Research has clearly shown that a change in approach that emphasizes allowing babies to develop fully when both mother and baby are doing well could result in healthier babies and lower medical costs. The campaign is called “Healthy babies are worth the wait.”
What prompted the campaign is what many experts view as an alarming trend in American obstetrics — the steady rise in elective deliveries of singleton babies before 39 weeks of gestation, when fetal development is complete. Gestation is calculated from the first day of a woman’s last menstrual period. Studies have shown that as many as 36 percent of elective deliveries now occur before 39 weeks, and many of these early deliveries are contributing to an unacceptable number of premature births and avoidable, costly complications.
Although guidelines issued 12 years ago by the American College of Obstetricians and Gynecologists cautioned against elective delivery by induction or Caesarean before 39 weeks, an overwhelming majority of new mothers and many doctors who deliver babies believe it is just as safe for birth to occur weeks earlier.
But the medical facts say otherwise. With each decreasing week of gestation below 39 to 40 weeks, there is an increased risk of complications like respiratory distress, jaundice, infection, low blood sugar, extra days in the hospital (including time in the neonatal intensive care unit), and even deaths of newborn babies and older infants.
Although tests may show that the baby’s lungs are well developed at, say, 37 weeks, research has demonstrated that the risk of newborn complications is still significantly higher than if delivery occurs two to three weeks later. In a study published last December of babies demonstrated to have mature lungs before birth, those delivered at 36 to 38 weeks had two and a half times the number of complications compared with those delivered at 39 to 40 weeks. Problems more common among babies delivered earlier in gestation included respiratory distress, jaundice and low blood sugar.
Yet in 2008 among a national sample of 650 women who had recently given birth, 51.7 percent chose 34 to 36 weeks of gestation as “the earliest point in pregnancy that it is safe to deliver the baby” and 40.7 percent chose 37 to 38 weeks. Only 7.6 percent selected 39 to 40 weeks, the true length of a full-term pregnancy, and the time when complications, including stillbirth, are least likely to occur.
Although many women think that weight gain is all that happens to babies during the last few weeks of pregnancy, Dr. Eve Lackritz, chief of the maternal and infant health branch of the national Centers for Disease Control and Prevention in Atlanta, said vital organs like the brain, lungs and liver are still developing. There are also fewer vision and hearing problems among babies born at full term.
“Babies aren’t fully developed until at least 39 weeks,” Dr. Lackritz told a news briefing in New York convened by the March of Dimes. For example, a baby’s brain at 35 weeks gestation weighs only two-thirds of what it will weigh at 39 to 40 weeks.
“If there are no medical complications, the healthiest outcome for both mother and infant is delivery at 40 weeks,” Dr. Lackritz said.
This is not to suggest that women should panic if labor begins earlier on its own. “It’s a whole different story when a woman goes into labor early than when labor is induced,” Dr. Uma M. Reddy of the National Institute of Child Health and Human Development said in an interview. She explained that the labor process helps to prevent lung problems. At the same gestational age, there are fewer respiratory problems when labor occurs naturally than when it is medically induced, Dr. Reddy said.
Dr. Reddy and colleagues analyzed more than 46 million singleton live births that occurred from 1995 to 2006 and found that newborn death rates at 37 weeks of gestation were two and a half to nearly three times the number at 40 weeks and were also elevated at 38 weeks of gestation. For example, in 2006 the infant mortality rate at 37 weeks gestation was 3.9 per 1,000 live births; at 38 weeks, 2.5 per 1,000 births; and at 40 weeks, 1.9 per 1,000 births. They reported their findings in the journal Obstetrics & Gynecology in June. The researchers also found that these so-called early-term births were associated with higher rates of death after birth and during infancy than were full-term births occurring at 39 to 41 weeks.
Dr. Reddy said that the textbook definition of “term pregnancy” as one that lasts from 37 to 41 weeks “is arbitrary — it has no biological basis. If a woman’s water hasn’t broken, if labor hasn’t begun on its own, if there are no medical or obstetrical problems, there’s no reason for a woman to be delivered before 39 weeks.”
The recommendation applies not just to women whose labor is induced, but also to those having a scheduled Caesarean delivery. Too often, women are mistaken about when they got pregnant, which can throw off the calculation of their due date. Even when a “dating”ultrasound is done during the first trimester of pregnancy, there can be as much as a two-week margin of error. Thus, a woman may think her pregnancy has lasted 39 weeks when it is only 37 weeks along. Or she may think she is 37 weeks pregnant when she is only 35 weeks; a delivery at that point would result in a premature birth.
Countering Early Elective Births
Dr. Reddy pointed out that “late preterm births” — between 34 and 37 weeks of gestation — in pregnancies with no complications are more common among older white women with higher levels of education who “are more likely to ask their obstetricians to deliver them before term.”
Well-educated women may be more inclined to want to schedule birth at a convenient time for themselves and other family members. Doctors, too, may suggest an elective delivery so that birth occurs at a time that best suits their schedules, including office hours and vacation times. Sometimes doctors, fearing a malpractice suit if something should go wrong if a pregnancy proceeds to term, choose to deliver babies early when they are alive and well.
To counter the avoidable complications and higher costs associated with preterm elective deliveries, beginning in January 2001 a network of nine urban hospitals in the Intermountain Healthcare system in Utah instituted a program to greatly limit elective deliveries before 39 weeks of gestation. The program included educational programs for doctors, nurses and pregnant women. However, not until strict monitoring of births was instituted by the hospitals did the rate of early deliveries drop to less than 3 percent from 28 percent, with a host of benefits but “no adverse effects” seen on the health of the mothers or babies.