Previous miscarriage and the subsequent risk of preterm birth in Scotland, 1980-2008: a historical cohort study

BJOG. 2015 Oct;122(11):1525-34. doi: 10.1111/1471-0528.13276. Epub 2015 Jan 28.


Objective: To determine whether the relationship between previous miscarriage and risk of preterm birth changed over the period 1980-2008, and to determine whether the pattern varied according to the cause of the preterm birth.

Design: Linked birth databases.

Setting: All Scottish NHS hospitals.

Population: A total of 732 719 nulliparous women with a first live birth between 1980 and 2008.

Methods: Risk was estimated using logistic regression.

Main outcome measures: Preterm birth, subdivided by cause (spontaneous, induced with a diagnosis of pre-eclampsia, or induced without a diagnosis of pre-eclampsia) and severity [extreme (24-28 weeks of gestation), moderate (29-32 weeks of gestation), and mild (33-36 weeks of gestation)].

Results: Consistent with previous studies, previous miscarriage was associated with an increased risk of all-cause preterm birth (adjusted odds ratio, aOR 1.26; 95% confidence interval, 95% CI 1.22-1.29). This arose from associations with all subtypes. The strongest association was found with extreme preterm birth (aOR 1.73; 95% CI 1.57-1.90). Risk increased with the number of miscarriages. Women with three or more miscarriages had the greatest risk of all-cause preterm birth (aOR 2.14; 95% CI 1.93-2.38), and the strongest association was with extreme preterm birth (aOR 3.87; 95% CI 2.85-5.26). The strength of the association between miscarriage and preterm birth decreased from 1980 to 2008. This was because of weakening associations with spontaneous preterm birth and induced preterm birth without a diagnosis of pre-eclampsia.

Conclusions: The association between a prior history of miscarriage and the risk of preterm birth declined in Scotland over the period 1980-2008. We speculate that changes in the methods of managing incomplete termination of pregnancy might explain the trend, through reduced cervical damage.

Keywords: Miscarriage; premature birth; spontaneous termination of pregnancy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abortion, Habitual / epidemiology
  • Abortion, Spontaneous / epidemiology*
  • Adult
  • Cohort Studies
  • Databases, Factual
  • Female
  • Humans
  • Pregnancy
  • Premature Birth / epidemiology*
  • Proportional Hazards Models
  • Risk
  • Scotland / epidemiology
  • Young Adult