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BJOG. 2015 Jun;122(7):973-81. doi: 10.1111/1471-0528.13007. Epub 2014 Jul 14.

Using inter-institutional practice variation to understand the risks and benefits of routine labour induction at 41(+0) weeks.

Author information

1
Perinatal Services British Columbia, Provincial Health Services Authority, Vancouver, British Columbia, Canada.
2
Department of Obstetrics & Gynaecology, University of British Columbia, Vancouver, British Columbia, Canada.
3
Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Quebec, Canada.
4
Department of Economics, McGill University, Montreal, Quebec, Canada.

Abstract

OBJECTIVE:

To evaluate the risks and benefits of routine labour induction at 41(+0) weeks' gestation for mother and newborn.

DESIGN:

Population-based retrospective cohort study of inter-institutional variation in labour induction practices for women at or beyond 41(+0) weeks' gestation.

POPULATION:

Women in British Columbia, Canada, who remained pregnant ≥41(+0) weeks and delivered at one of the province's 42 hospitals with >50 annual deliveries, 2008-2012 (n = 14,627).

METHODS:

The proportion of women remaining pregnant a week or more past the expected delivery date who were induced at 41(+0) or 41(+1) weeks' gestation for an indication of 'post-dates' was calculated for each institution. We used instrumental variable analysis (using the institutional rate of labour induction at 41(+0) weeks as the instrument) to estimate the effect of labour induction on maternal and neonatal health outcomes.

MAIN OUTCOME MEASURES:

Caesarean delivery, instrumental delivery, post-partum haemorrhage, 3rd or 4th degree lacerations, macrosomia, neonatal intensive care unit admission, and 5-minute Apgar score <7.

RESULTS:

Institutional rates of labour induction at 41(+0) weeks ranged from 14.3 to 46%. Institutions with higher (≥30%) and average (20-29.9%) induction rates did not have significantly different rates of caesarean delivery, instrumental delivery, or other maternal or neonatal outcomes than institutions with lower induction rates (<20%). Instrumental variable analyses also demonstrated no significantly increased (or decreased) risk of caesarean delivery (0.69 excess cases per 100 pregnancies [95% CI -10.1, 11.5]), instrumental delivery (8.9 per 100 [95% CI -2.3, 20.2]), or other maternal or neonatal outcomes in women who were induced (versus not induced).

CONCLUSIONS:

Within the current range of clinical practice, there was no evidence that differential use of routine induction at 41(+0) weeks affected maternal or neonatal health outcomes.

KEYWORDS:

Caesarean delivery; instrumental variable; labour induction; post-dates; prolonged pregnancy

PMID:
25041161
DOI:
10.1111/1471-0528.13007
[Indexed for MEDLINE]
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