The overlap between miscarriage and extreme preterm birth in a limited-resource setting on the Thailand-Myanmar border: a population cohort study

Abstract

Background: Countries vary on the demarcation gestational age that distinguishes miscarriage and extreme preterm birth (PTB). This study provides a synopsis of the outcome of pregnancy between 22 to <28 weeks’ gestation from a low resource setting. Methods: A retrospective record review of a refugee and migrant population on the Thailand-Myanmar border with outcome between 22 to <28 weeks’ gestation, was conducted. Outcomes were classified as miscarriage: non-viability prior to 22 week’s gestation with expulsion of products between 22 to < 28 weeks’ gestation; or extreme PTB when the fetus was viable at ≥22 weeks and delivered between 22 to < 28 weeks’ gestation. Termination of pregnancy and gestational trophoblastic disease were excluded. Results: From 1995-2015, outcomes occurred between 22 to <28 weeks’ gestation in 0.9% (472/49,931) of pregnancies and 3.8% (18/472) met the exclusion criteria. Most included pregnancies (n=454) had ultrasound done 72.5% (n=329). Overall 43.6% (n=197) were miscarriage and 56.4% (n=257) extreme PTB. Miscarriage (late expulsion) between 22 to <28 weeks was observed with non-viability occurring at an estimated median gestation of 16 weeks. For cases with available data (n=252, 5 missing) the proportion of stillborn was 47.6% (n=120), liveborn 52.4% (n=132); and congenital abnormality 10.5% (24/228, 29 missing). Neonatal death was high 98.5% (128/131, 1 missing). Introduction of ultrasound was associated with a 2-times higher odds of classification of outcome as birth rather than miscarriage. Conclusion: In this low resource setting <1% of pregnancy outcomes occur in the 22 to <28 weeks’ gestation window; nearly half  were miscarriage; and neonatal mortality approached 100%.  In the scale-up to preventable newborns deaths, at least initially, greater benefits will be obtained by focusing on the greater number of viable newborns with a gestation of 28 weeks or more.