Conceiving within a year or even 6 months after a stillbirth did not increase a woman's likelihood of having another stillbirth or a preterm or small for gestational age (SGA) baby compared with an interpregnancy interval of at least 2 years, according to a new study published online February 28 in the Lancet.
The results are from the first large-scale observational study to investigate the interval between stillbirth and subsequent pregnancy, including almost 14,500 births in women from Australia, Finland, and Norway who had a stillbirth in their previous pregnancy.
"Approximately 3.5 in every 1000 births in high-income countries are stillborn, and there is limited guidance available for planning future pregnancies. We hope that our findings can provide reassurance to women who wish to become pregnant or unexpectedly become pregnant shortly after a stillbirth,” said lead author Annette K. Regan, PhD, of Curtin University, Perth, Australia, in a Lancet press release.
Currently, the World Health Organization recommends that women do not attempt to conceive until at least 6 months after a miscarriage or abortion and at least 2 years after a live birth, but there are no recommendations for the optimal interval after a stillbirth (defined as fetal loss after midpregnancy).
The new study attempted to fill this evidence gap by pooling data from population-level birth registries in three countries over an almost 40-year period.
The data "consistently showed that an interpregnancy interval of less than 1 year was not associated with increased risk of adverse birth outcomes in the next pregnancy. Our findings provide valuable evidence for recommended pregnancy spacing after a stillbirth," added Regan.
In an invited commentary, Mark A. Klebanoff, MD, of the Center for Perinatal Research at Nationwide Children's Hospital in Columbus, Ohio, says: "The results...suggest that interpregnancy interval [after stillbirth] might be less important than previously assumed, at least 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."
Within a Year of a Stillbirth, 63% of Women Became Pregnant Again
Using birth records data from 1987-2016 in Finland, 1980-2015 in Norway, and 1980-2015 in Western Australia, the researchers analyzed birth outcomes in women who had conceived following a singleton stillbirth at 22 weeks' gestation or later. Among the subsequent 14,452 births, 2% were stillbirths, 18% were preterm, and 9% were SGA. Most of the stillbirths (88%) were preterm; 12% were at term.
The median time between a woman's stillbirth and the start of her next pregnancy was 9 months, with 63% of women conceiving within 12 months (and 37% conceiving within 6 months) after stillbirth.
Women who conceived less than 6 to 12 months after a stillbirth did not have a greater odds of a stillbirth, preterm birth, or SGA newborn than women who conceived 24 to 59 months after their stillbirth, after adjustment for a women's country, age, parity, decade of delivery, and duration of preceding pregnancy.
Additional adjustment for educational level and maternal smoking during pregnancy, when those data were available, also did not change the findings, nor did investigation of only births after 1998.
Despite their statistical adjustments, the authors note that other confounders may yet turn out to play a role in the findings.
"Women who conceive soon after a previous pregnancy might be healthier and more fertile than women who conceive later and therefore could be less prone to adverse birth outcomes," they hypothesize. And they acknowledge they lacked data on women's chronic conditions, intent to conceive, socioeconomic status, stillbirth cause, miscarriages, abortions, or use of assisted reproductive technology.
Results Informative but Require Replication as Stillbirths Are Rare
The results come from high-income countries with universal healthcare, free antenatal care, and predominantly white populations, potentially precluding generalization to low- or middle-income nations, countries without access to universal healthcare, or ethnic minorities, Regan and colleagues add.
Klebanoff agrees, noting "the results might not apply to women in less favorable situations in which malnutrition, untreated chronic medical conditions, and poor access to quality medical and obstetric care are common."
The researchers also note that although this is the largest study of its kind, only 228 women had recurrent stillbirths, which means the analyses for this group are limited because of small numbers. Replication of the study in a larger group would be informative, they conclude.
The research was funded by Australia's National Health and Medical Research Council, the Research Council of Norway, and the UK Medical Research Council. The authors have reported no relevant financial relationships.
Lancet. Published online February 28, 2019.
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