Researchers Tie Subfertility to Higher Risk of Neonatal Death


Women who do not conceive within 1 year of trying may face an increased risk of their babies dying by the first month post partum, according to Danish researchers.

“Subfecundity may be associated with an increased risk of neonatal death and should be included as a risk indicator in neonatal care,” reported Olga Basso, Ph.D., and Jørn Olsen, M.D., from the Danish Epidemiology Center at the University of Aarhus in Denmark (BMJ [Epub ahead of print], Feb. 4, 2005. Article DOI number: 10.1136/bmj.38336.616806.8F).

“Unlike advanced age, or pregnancy following in vitro fertilization, a period of infertility is not routinely considered a risk factor in pregnancy,” Dr. Basso told this newspaper. “We think it would be advisable to include this when evaluating pregnant women, because it is possible that some complications might be noticed earlier,” she said.

The study analyzed 27,329 singleton births and 66 deaths recorded in the Danish national birth cohort. The analysis was restricted to primiparous women, 73.5% of whom had no previous pregnancies.

The women were grouped by waiting time to pregnancy: up to 2 months (reference group); 3-12 months; more than 12 months with no infertility treatment; more than 12 months with infertility treatment; and those who hadn't planned their pregnancy.

After adjustment for maternal age, body mass index, smoking, and social class (derived from the mother's job title), the analysis found an increased risk of neonatal death associated with increasing time to pregnancy.

Women who reported trying to conceive for more than 12 months had an odds ratio (OR) of 2.80 for neonatal death. Within this group, there was little difference in risk between those who reported infertility treatment (OR 2.21), and those who reported none (OR 3.38).

The authors noted potential weaknesses in their data. About 35% of eligible women participated in the study, and the mother's job title may be a poor proxy for social class (even though adjustment for confounders did not change the estimates). Moreover, subfertile women who do not seek fertility treatment may also not seek or receive adequate prenatal care.

The researchers noted that the findings do not indicate a causal relationship.

“Our finding needs … to be corroborated elsewhere before it can be stated that a long time to pregnancy increases the risk of neonatal death,” they said.

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