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Pregnancies shortly after a stillbirth were not linked with an increased risk of adverse outcomes compared to those where women waited longer to conceive, researchers found.

In a study of over 14,000 women who had a stillbirth, pregnancy intervals ≤12 months were not associated with a higher risk of subsequent stillbirth, preterm birth, or small-for-gestational-age birth compared with intervals of 24-59 months following a stillbirth, reported Annette Regan, PhD, of Curtin University in Perth, Australia, and colleagues in .

Researchers noted that the World Health Organization that women wait ≥2 years after a live birth and 6 months after a miscarriage or induced abortion before attempting conception again, but "no recommendation exists for the optimal interpregnancy interval after a stillbirth."

"Without sufficient time to recover from a previous pregnancy, women may be at increased risk of entering a reproductive cycle with poor nutritional status, which has been linked to increased risk of [fetal] growth restriction and birth defects," Regan said in a statement. "Such nutritional depletion might not occur to the same extent after a pregnancy loss, and this may affect the optimal interpregnancy interval, explaining why it may be different after stillbirth and live birth."

Prior research suggested that an interpregnancy interval ≤6 months after live birth is linked with a nearly twofold increase in adverse pregnancy outcomes, and only two previous studies have examined the association between interpregnancy interval following stillbirth and later pregnancy outcomes, the authors noted, though neither "specifically aimed" to examine this situation.

For the current study, Regan's group examined birth records from Finland, Norway, and Australia for women whose most recent pregnancy ended in stillbirth of ≥22 weeks gestation.

Overall, researchers analyzed data from 14,552 singleton births among mothers with a stillbirth in a previous singleton pregnancy. Median interpregnancy interval after still birth was 9 months versus 25 months after a live birth. About two-thirds of women conceived their next child ≤12 months after stillbirth, with a little over a third conceiving within 6 months.

Of the examined subsequent births, 2% were stillbirths, 18% were preterm births, and 9% were small-for-gestational-age births.

When compared to women with interpregnancy intervals of 24-59 months, interpregnancy intervals of even <6 months were not linked to increased risk of adverse pregnancy outcomes, including:

• Subsequent stillbirth (pooled adjusted OR 1.09, 95% CI 0.63-1.91)
• Preterm birth (pooled adjusted OR 0.91, 95% CI 0.75-1.11)
• Small-for-gestational-age birth (pooled adjusted OR 0.66, 95% CI 0.51-0.85)

Similarly, there were no increased odds of these outcomes when comparing interpregnancy intervals of 6-11 months versus 24-59 months.

Moreover, the authors found no differences in the link between interpregnancy interval and birth outcomes by gestational length of the previous stillbirth, they noted.

An by Mark A. Klebanoff, MD, of the Research Institute at Nationwide Children's Hospital in Columbus, Ohio, said that the results of this study suggest that pregnancy interval after stillbirth "might be less important than previously assumed" for women in high-income regions.

"Rather than adhering to hard and fast rules, clinical recommendations should consider a woman's current health status, her current age in conjunction with her desires regarding child spacing and ultimate family size, and particularly following a loss, her emotional readiness to become pregnant again," he wrote.

Indeed, Regan and colleagues noted that because 37% of women became pregnant within 6 months of a stillbirth, and 63% became pregnant within 12 months, "these results apply to a large proportion of women conceiving after a stillbirth."

Limitations to the data include the observational nature of the study, and unmeasured confounders that have the potential to affect findings. They also said that the countries included in the study "have access to universal healthcare and free antenatal care, and the populations are primarily white," limiting their generalizability to low- or middle-income countries, ethnic minority groups, or countries without access to universal healthcare, the authors said.