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

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

Author information

1
Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK.
2
Information Services Division, NHS National Services Scotland, Edinburgh, UK.
3
Department of Obstetrics and Gynaecology, NIHR Biomedical Research Centre, University of Cambridge, Cambridge, UK.

Abstract

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

PMID:
25626593
PMCID:
PMC4611958
DOI:
10.1111/1471-0528.13276
[Indexed for MEDLINE]
Free PMC Article

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