Grand Rounds

Benefit or Risk to Delaying Pregnancy after Miscarriage?

BACKGROUND AND PURPOSE:

There is no consensus on how long to wait prior to attempting pregnancy after fetal loss
As the age of first pregnancy continues to rise in some parts of the world, waiting may be detrimental
Sundermann et al. (Obstetrics & Gynecology, 2017) sought to determine whether interpregnancy interval length after pregnancy loss is linked with higher risk of repeat miscarriage

Prospective cohort study (2000-2012)
Eligibility: Early in pregnancy or planning pregnancy, whose most recent pregnancy before enrollment ended is miscarriage
- All women enrolled prior to 12 weeks gestation
- No use of assisted reproductive technologies
- Dating by first trimester ultrasound
Miscarriage: Defined as loss before 20 weeks of gestation
Primary outcome: Pregnancy loss before 20 weeks gestation in the study pregnancy
Adjusted models included maternal age, race, parity, body mass index, and education

Of the 514 women participating in the study, 15.7% had repeated miscarriage
- Median gestation age 9 weeks
Median maternal age was 30 years and 55.6% of participants had at least one previous livebirth
9% had ≥ losses at time of enrollment
When compared with women with interpregnancy intervals of 6–18 months
- Intervals < 3 months associated with lowest risk of repeat miscarriage (7.3% compared with 22.1%; adjusted hazard ratio 0.33, 95% CI 0.16–0.71)
- Risk was not modified by maternal race nor parity
Trend showed similar results when interpregnancy interval was analyzed as as a continuous variable
- Risk of subsequent miscarriage lowest for women with short interpregnancy intervals and increasing with longer intervals until reaching a peak at 6 months

A shorter interpregnancy interval of less than 3 months was associated with the lowest risk of subsequent miscarriage
Authors suggest various biologic mechanisms, including that the body may be primed for pregnancy in the few months after miscarriage
Delaying conception to reduce miscarriage risk is not advisable

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