Role of Maternal Age and Pregnancy History in Risk of Miscarriage: Prospective Register-based Study

M.C Magnus,S.E Håberg,A.J Wilcox,N.H Morken,C.R Weinberg

doi:10.1097/01.aoa.0000603692.53662.e1

Abstract

(BMJ. 2019;364:I869) Miscarriage is unfortunately a relatively common pregnancy outcome. Various studies have reported that 12% to 15% of pregnancies end in miscarriage. However, these rates may not be accurate as some women experience miscarriage without ever realizing they were pregnant and differences exist among studies regarding the definition of miscarriage versus stillbirth. Several risk factors for miscarriage have been reported, but maternal age seems to have the strongest association. The youngest mothers have a slightly increased risk while older women have a much greater risk than younger women. There might also be an association between previous pregnancy complications and miscarriage risk. This population-based study aimed to evaluate the rate of miscarriage and its association with maternal age and pregnancy history among Norwegian women.

Highlights

Miscarriage is a common outcome of pregnancy, with most studies reporting 12% to 15% loss among recognised pregnancies by 20 weeks of gestation.[1,2,3,4] Quantifying the full burden of miscarriage is challenging because rates of pregnancy loss are high around the time that pregnancies are clinically recognised
The risk of miscarriage was modestly increased if the previous birth ended in a preterm delivery, stillbirth (1.30, 1.11 to 1.53), caesarean section (1.16, 1.12 to 1.21), or if the woman had gestational diabetes in the previous pregnancy (1.19, 1.05 to 1.36)
Miscarriage is a common pregnancy outcome with a substantial recurrence risk The risk of miscarriage increases strongly with maternal age There is a small increase in the risk of miscarriage in the youngest mothers

Summary

Introduction

Miscarriage is a common outcome of pregnancy, with most studies reporting 12% to 15% loss among recognised pregnancies by 20 weeks of gestation.[1,2,3,4] Quantifying the full burden of miscarriage is challenging because rates of pregnancy loss are high around the time that pregnancies are clinically recognised. A general lack of data on induced abortions has made it difficult to determine how seriously this competing risk distorts the estimation of miscarriage rates. Based on national registries or population based cohort studies, the reported risk of miscarriage in Sweden, Finland, and Denmark was between 12.9% and 13.5%.5-7A previous Norwegian study included all women treated at one of the main hospitals in Oslo between 2000 and 2002, and estimated a miscarriage rate of 12% when taking into account induced abortions.[8]

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