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Abstract
Objectives After introduction of a more proactive post-term induction practice, stillbirth rates have decreased substantially throughout the first decade of this century in Denmark. The aim was to follow up on induction and stillbirth rates in Denmark.
Design Historical ecological study.
Participants We included all delivering women in Denmark during the period 2007–2018.
Intervention Induction rates from 41 weeks of gestation.
Main outcome measure Stillbirth rates from 41+0 weeks.
Results Of 739 570 delivered children, 179 734 (24.3%) were born from 41+0 weeks. The proportion of deliveries after 41 weeks which were induced increased from 25.4% in 2007 to 44.4% in 2012. From 2012 to 2015, the induction rates decreased from 44.4% to 39.4%. After 2015 rates were stable.
During the same period, stillbirth rates decreased from 1.30 in 2007/2008 to 0.38 per 1000 newborn in 2011/12; -54%. From 2012, however, the rates were doubled from 0.38 per 1000 in 2011/2012 to 0.74 per 1000 in 2015/2018; RR 1.97 (95% CI 1.02 to 3.81), p=0.033.
Changes in the included potential confounders cannot explain neither the substantial fall in stillbirth rates from 2007/2008 to 2011/2012, nor the doubling in stillbirth rates after 41 weeks since 2012.
During the whole study period, the cumulated risk of intrauterine foetal death increased from week 41+0 to 41+6 from 0.16 to 1.25 per 1000 ongoing pregnancies or 7.8 folds. Going beyond 42 weeks further increased the risk to 2.46 per 1000 ongoing pregnancies.
Conclusion We found a consistent inverse correlation between the proportion of women with induction of labour after 41 weeks of gestation and the stillbirth rates during the same period and same gestational ages. This Danish update on post-term inductions and corresponding stillbirth rates thus confirm previous findings suggesting a causal link between these two parameters.
- epidemiology
- fetal medicine
- maternal medicine
- perinatology
- public health
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Footnotes
Contributors ØL, LK and AT conceptualised the study, ØL made the analyses and wrote first draft of paper. All authors, ØL, LK, AT, NPD and OBBP, interpreted the results, revised the manuscript and accepted the final version.
Funding OBBP holds a professorship funded by Novo Nordisk Foundation grant NNFSA170030576. Expenses were covered by department of Gynaecology.
Disclaimer The actual study did not receive any funding.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Patient consent for publication Not required.
Ethics approval Most data are publicly available at e-sundhed.dk. Data for the detailed analysis on different gestational days were delivered by permission from the Regional Data Protection Agency: J no P-2020–217.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as online supplemental information. All data relevant to the study are included in the article. Only authorised scientists can after relevant permissions from the Danish Data Protection Agency get access to individual medical data in Danish registries.