Labor should not be induced before the 39th week of pregnancy unless there's a clear medical reason to do so. It puts newborns at risk for respiratory and other health problems. Even one week makes a significant difference.

That's according to a study by Intermountain Health Care of the 85,000 newborns delivered in its health-care system from 2000-2003. Dr. Bryan Oshiro, medical director of the Women's and Newborn Program at IHC, presented the findings at the national gathering of obstetricians and gynecologists recently. Tuesday, he discussed the issue in a media briefing at LDS Hospital.

A trend has developed toward "convenience" inductions, where medication is given to start labor early. Sometimes moms are sick of the pregnancy and just want it done. Or Grandma may be coming to town a certain week and already has her plane ticket. Sometimes, the doctor's going to be out of town later and "I want him to deliver my baby," Oshiro said he's been told.

Those reasons don't outweigh the risk to newborns, he said. The result too often is normal-sized babies in the newborn intensive care unit on ventilators. Besides that, inducing labor earlier usually results in longer labor because the cervix is not ready, increases the likelihood of needing a Caesarean section delivery to as much as 50 percent and increases likelihood of infections. All of those also add to the expense.

Marissa Burridge was likely as tired of being pregnant as any woman, but inducing early never occurred to her or husband Christian, she said during the news conference.

"You always get the urge" at the end of pregnancy, she said. Still, without any particular complications or reason to deliver Alma early, she followed the recommendation to wait. Increasingly, nationwide, however, pregnant woman have moved delivery up as a matter of convenience.

Research has shown that physicians who have not really examined the issue tend to believe it's not a problem, Oshiro said. IHC has developed an education campaign for doctors and parents on the importance of waiting if the induced labor is elective. It's a different story if there are medical reasons to start labor.

The numbers speak clearly on the topic, Oshiro said. When labor is induced at 39 weeks, admissions to the intensive care unit dropped by nearly two-thirds, when compared to labor induced at 37 weeks. Normal human gestation is 40 weeks.

Oshiro said when the study started, nearly a third of mothers at IHC facilities were given medication to start labor, similar to the national average. At IHC it has now dropped to about 5 percent.

Babies delivered at 39 weeks or later are the least likely group of newborns to need to be on a ventilator, Oshiro said. And while that extra week is crucial for lung development, for example, there's no evidence that it harms moms, increases incidence of toxemia, or even that the babies get significantly bigger.

There are very good reasons to induce labor early, Oshiro added, such as if the baby's too small and not growing well, or Mom lives in a rural community and has a history of going into labor early and delivering very quickly.

Risks associated with labor and delivery at 39, 40 and 41 weeks are about the same, he said. Then it increases again.

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E-mail: lois@desnews.com