Preterm prelabour rupture is becoming commoner in France

Design

exploratory population-based study using national administrative health data, negative binomial mixed model for trend and BYM2 spatial model

Population

150,615 pregnancies with a diagnosis of prelabour rupture of membranes before 37 weeks, metropolitan France, 2015-2023

Primary outcome

annual crude incidence and spatial variation of preterm prelabour rupture of membranes

Effect

incidence rate ratio 1.023 per year (95% CI 1.017-1.030), crude incidence 2.2% in 2015 to 2.7% in 2023; 2020 IRR 0.903 (0.887-0.920)

Preterm prelabour rupture of membranes drives a large share of preterm birth, and whether its incidence is changing has been hard to answer because it is rarely counted at population level. This study used the French National Health Data System to identify every pregnancy with a first hospitalisation carrying a diagnosis of rupture before 37 weeks between 2015 and 2023 — 150,615 cases, about 16,700 a year.

Incidence rose steadily, with an incidence rate ratio of 1.023 per year (95% CI 1.017-1.030), taking the crude annual figure from 2.2% of live births in 2015 to 2.7% in 2023. The exception was 2020, which fell relative to the trend (IRR 0.903, 0.887-0.920). Smoothed standardised incidence ratios mapped by department showed clear geographical inequality.

Administrative data identify hospitalisations with a diagnostic code, so part of a rising trend can always be coding, awareness or changes in admission thresholds rather than biology. The 2020 dip is a reminder of that — it is far more likely to reflect how the health system behaved that year than a real fall. What the geography does is generate hypotheses: the authors point at environmental exposures, and deprivation, smoking, infection and access to antenatal care are the usual candidates. Nothing here changes management of an individual woman, but a departmental audit of local rates is a reasonable response.

• This is surveillance data — it describes where and when, not why
• The 2020 dip almost certainly reflects health system behaviour, not a real fall in incidence
• Geographical variation is a prompt for local audit rather than an explanation
• Management of the individual woman with preterm rupture is unchanged
• Where local rates are high, check the modifiable contributors: smoking, genital infection, antenatal access

The statistics, in plain English

An incidence rate ratio of 1.023 per year compounds to roughly a 20% relative rise over the study period — real but modest, and precisely estimated only because the denominator is a whole country. Spatial smoothing with a BYM2 model borrows information between neighbouring departments, which stabilises estimates in small areas but also blurs genuinely isolated hotspots. Because cases are defined by hospitalisation coding, any change in how rupture is coded or admitted over nine years enters the trend directly.

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