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. 2023 Jan;130(1):33-41.
doi: 10.1111/1471-0528.17291. Epub 2022 Oct 3.

Iatrogenic and spontaneous preterm birth in England: A population-based cohort study

Harriet Aughey  1   2 , Jennifer Jardine  1   3 , Hannah Knight  1   3 , Ipek Gurol-Urganci  3 , Kate Walker  3 , Tina Harris  1   4 , Jan van der Meulen  1   3 , Jane Hawdon  1   5 , Dharmintra Pasupathy  1   6 ; NMPA Project Team  1
Collaborators, Affiliations

Iatrogenic and spontaneous preterm birth in England: A population-based cohort study

Harriet Aughey et al. BJOG. 2023 Jan.

Abstract

Objective: To describe the rates of and risk factors associated with iatrogenic and spontaneous preterm birth and the variation in rates between hospitals.

Design: Cohort study using electronic health records.

Setting: English National Health Service.

Population: Singleton births between 1 April 2015 and 31 March 2017.

Methods: Multivariable Poisson regression models were used to estimate adjusted risk ratios (adjRR) to measure association with maternal demographic and clinical risk factors.

Main outcome measures: Preterm births (<37 weeks of gestation) were defined as iatrogenic or spontaneous according to mode of onset of labour.

Results: Of the births, 6.1% were preterm and of these, 52.8% were iatrogenic. The proportion of preterm births that were iatrogenic increased after 32 weeks. Both sub-groups were associated with previous preterm birth, extremes of maternal age, socio-economic deprivation and smoking. Iatrogenic preterm birth was associated with higher body mass index (BMI) (BMI >40 kg/m2 adjRR 1.59, 95% CI 1.50-1.69) and previous caesarean (adjRR 1.88, 95% CI 1.83-1.95). Spontaneous preterm birth was less common in women with a higher BMI (BMI >40 kg/m2 adjRR 0.77, 95% CI 0.70-0.84) and in women with a previous caesarean (adjRR 0.87, 95% CI 0.83-0.90). More variation between NHS hospital trusts was observed in rates of iatrogenic, compared with spontaneous, preterm births.

Conclusions: Just over half of all preterm births resulted from iatrogenic intervention. Iatrogenic births have overlapping but different patterns of maternal demographic and clinical risk factors to spontaneous preterm births. Iatrogenic and spontaneous sub-groups should therefore be measured and monitored separately, as well as in aggregate, to facilitate different prevention strategies. This is feasible using routinely acquired hospital data.

Keywords: iatrogenic; induction; preterm birth; spontaneous.

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Conflict of interest statement

The authors declare no conflict of interests. HA, JJ, HK, JH, TH, IGU, DP have all received support to deliver the National Maternity and Perinatal Audit. JvdM chairs the National Maternity and Completed disclosure of interests form available to view online as supporting information.

Figures

FIGURE 1
FIGURE 1
Risk‐adjusted patterns of association for spontaneous and iatrogenic preterm birth among 963 800 women who gave birth in England between 1 April 2015 and 31 March 2017. Note that the relationship with previous preterm birth is outwith the axis because of the strength of association (spontaneous preterm birth adjusted risk ratio [adjRR] 6.53, 95% CI 6.32–6.75; iatrogenic preterm birth adjRR 3.34, 95% CI 3.22–3.46).
FIGURE 2
FIGURE 2
Funnel plots showing the risk‐adjusted proportion of singleton preterm births by trust of birth: (A) total preterm birth, (B) spontaneous preterm birth and (C) iatrogenic preterm birth.
See this image and copyright information in PMC

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