Risk of Delaying Childbirth Is Small

It could be described as an older-mom baby boom. In the U.S. the birth rate among women over 35 has risen steadily over the last two decades, and 40-plus celebrity moms and their babies routinely grace the covers of women's magazines.

While later-life childbirth now seems routine, it is not without increased risk for the baby beyond the well-established increase in genetic disorders like Down syndrome, a new study confirms.

Compared with babies born to moms in their early to mid-20s, babies born to older mothers have a higher risk of death and are more likely to be born prematurely, underweight, or have other birth-related problems.

But while the risk for older moms is clearly higher, it is still very small, says the study's researcher.

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'Best Time in History' for Later Childbirth

In the study, women 40 and over were twice as likely to have babies who died at birth as women in their early to mid-20s. But only about 11 deaths occurred in the study for every 1,000 births to older women, compared to six for the younger women.

"Biologically speaking, older women are at a disadvantage, but from a medical and technological point of view this is the best time in history for a woman to have a baby at a later age," K.S. Joseph, MD, PhD, tells WebMD.

"Given that so many women are choosing to have their babies at a later age, it is reassuring that the absolute risk of something going wrong is fairly low."

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The Real Risks

The study population included all women living in Nova Scotia, Canada, who delivered single babies between 1988 and 2002. Information on pregnancy, labor, delivery, and newborn follow-up was obtained from a population database. Other information on the women's social and economic status was obtained from tax records and other sources.

The findings are reported in the June issue of the journal Obstetrics and Gynecology.

The researchers reported that women who gave birth at later ages were more likely than younger women to be married and economically well off. They were more likely to attend prenatal classes, weigh more, and have previous pregnancies with poor outcomes.

They were also more likely to develop complications during pregnancy such as high blood pressure, type 2 diabetes, and placental separation. The increased risks steadily climbed starting at age 25 and up.

Older women were also more likely to have induced labors and cesarean deliveries.

The older the mom — starting at age 25 — the higher the risk of having a preterm birth or a low- birth-weight baby.

The risk of having a baby die shortly before or shortly after birth or have serious problems at birth began to rise at the age of 35. Before that age, the researchers found no significant increase in such problems.

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The overall frequency of birth-related deaths or serious illness was as follows (note the numbers are very similar up to the age of 35):

—13 per 1,000 births among babies born to women aged 20 to 24

—12 per 1,000 births among babies born to women aged 25 to 29

—11 per 1,000 births among babies born to women aged 30 to 35

—15 per 1,000 births among babies born to women aged 35 and 39

—19 per 1,000 births among babies born to women 40 and over

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Cautious Optimism

Joseph tells WebMD that older pregnant women who follow their doctor's advice can be "cautiously optimistic" that their baby will be born healthy.

But epidemiologist and pregnancy researcher Suzanne Tough, PhD, worries that women don't really understand the long-term risks of delayed childbirth or aren't being told about them.

She says older women are very aware that they may have a harder time getting pregnant and most know that their risk of having a child with Down syndrome is higher.

"But they often don't recognize that once they have achieved a pregnancy there is a higher rate of miscarriage, preterm and low-birth-weight deliveries, and multiple births," she tells WebMD.

Tough's own research suggests that delayed childbirth may be largely responsible for the increasing number of low-birth-weight and preterm babies, especially in urban areas. The implications of this increase reach far beyond the family, she says.

"These are children who may require extra support in school or who may require all kinds of interventions for years to come," she says. "When we talk from a health care perspective about how to tackle this rising low-birth-weight issue, we need to acknowledge that one of the primary risk factors is delayed childbirth."

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By Salynn Boyles, reviewed by Michael W. Smith, MD

SOURCES: Joseph, K.S. Obstetrics and Gynecology, June 2005; vol 205: pp 1410-1418. K.S. Joseph, MD, PhD, perinatal epidemiologist; associate professor, department of obstetrics and gynecology, Dalhousie University, Halifax, Nova Scotia. Suzanne Tough, PhD, MSc, faculty of medicine, University of Calgary.