Study challenges guidelines for pregnancy timing after miscarriage, abortion
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Researchers identified no increased risk for adverse pregnancy outcomes in pregnancies conceived within 3 months vs. 6 to 11 months after miscarriage or abortion, according to data published in PLOS Medicine.
“The current World Health Organization recommendation is for a woman to wait at least 6 months after miscarriage and induced abortion before becoming pregnant again to avoid complications in the next pregnancy,” Gizachew Tessema, PhD, MPH, a senior research fellow at Curtin University School of Population Health in Perth, Australia, told Healio. “Since the original recommendation was largely informed based on limited studies from low- and middle-income countries, we would like to evaluate whether there is increased risk of adverse pregnancy outcomes following short pregnancy interval after a miscarriage or an induced abortion in high-income countries, particularly in Norway.”
Tessema and colleagues retrospectively analyzed data from the Medical Birth Registry of Norway, the Norwegian Patient Registry and Norway’s General Practitioner database. These data were used to identify pregnancies with an estimated conception date between 2008 and 2016.
In total, the researchers included 49,058 pregnancies after miscarriage that resulted in births and 23,707 pregnancies after induced abortion that resulted in birth. Each birth was categorized into six groups based on interpregnancy intervals (IPIs): less than 3 months, 3 to 5 months, 6 to 11 months, 12 to 17 months, 18 to 23 months and 24 or more months. Six to 11 months was the reference for all outcomes, which included preterm birth, spontaneous preterm birth, size at gestational age, preeclampsia and gestational diabetes.
Miscarriage
Having a pregnancy within 3 months vs. 6 to 11 months after miscarriage was associated with lower risks for small for gestational age (adjusted RR = 0.85; 95% CI, 0.79-0.92) and gestational diabetes (aRR = 0.85; 95% CI, 0.75-0.96).
An IPI of 3 to 5 months after miscarriage was also associated with a lower risk for small for gestational age (aRR = 0.9; 95% CI, 0.83-0.97) after miscarriage.
Longer IPIs after miscarriage were associated with gestational diabetes risk only. Specifically, compared with an IPI of 6 to 11 months, the risk was greater in births with an IPI of 12 to 17 months (aRR = 1.2; 95% CI, 1.02-1.4) and 18 to 23 months (aRR = 1.24; 95% CI, 1.02-1.5).
“In our study, although we found no association between short IPI after miscarriages and adverse pregnancy outcomes, the results indicating a modest increased risk of gestational diabetes mellitus after 12 months after miscarriages was unexpected and this calls for further study,” Tessema said.
Abortion
Pregnancies conceived within 3 months of an induced abortion were associated with a nonsignificant increased risk for small for gestational age compared with pregnancies conceived between 6 and 11 months following an abortion. There was a lower risk for large for gestational age with an IPI of 3 to 5 months vs. 6 to 11 months (aRR = 0.84; 95% CI, 0.72-0.98).
An IPI after induced abortion longer than 12 months was not associated with adverse pregnancy outcomes, according to the study.
“The findings are reassuring for women or families who attempt conceiving shortly after miscarriages or induced abortions,” Tessema said. “Next, we would like to investigate if there is association between previous miscarriage and risk of gestational diabetes mellites in the subsequent pregnancy.”