Risk factors for antepartum and intrapartum stillbirth at 20-23 weeks gestation

Risk factors for antepartum and intrapartum stillbirth at 20-23 weeks gestation

Brad M Farrant (1), Helen D Bailey (1), Eva Malacova (2), Gavin Pereira (3), Danielle Pollock (4), Scott W White (5), Carrington CJ Shepherd (1)

(1) Telethon Kids Institute, The University of Western Australia, Perth, Western Australia. (2) QIMR Berghofer Institute of Medical Research. (3) Curtin University. (4) University of South Australia. (5) King Edward Memorial Hospital, University of Western Australia.

1) Background:
Half of stillbirths (20+ weeks gestation) in Western Australia (WA) occur at 20-23 weeks. However, there is a lack of research identifying risk factors. We sought to identify factors that predict antepartum and intrapartum stillbirth at 20-23 weeks using the broad range of linked data available from the WA Data Linkage System.

2) Methods:
In this population-based cohort study of singleton births, we analysed de-identified linked data from core health datasets. Data on intrapartum stillbirths were available for 2005-2015 and antepartum stillbirths for 2011-2015. Intrapartum stillbirths were classified as occurring after spontaneous labour onset with intact membranes (SPON), spontaneous rupture of membranes prior to labour (PROM), or medically indicated (MI) where labour was induced or caesarean section occurred prior to labour or PROM (the SPON and PROM groups excluded, and the MI group included, cases with birth defects and/or medical terminations). Logistic regression was used to calculate the odds (OR) of antepartum and intrapartum (SPON, PROM, MI) stillbirth associated with each risk factor in comparison with SPON term livebirths (the preferred outcome).

3) Results:
Complete sets of data were available for 623 singleton stillbirths including 112 (18%) antepartum, 81 (13%) SPON, 77 (12%) PROM, and 353 (57%) MI (including 310 medical terminations). While univariate and multivariate analyses identified common risk factors (e.g., extremely small for gestational age baby, threatened miscarriage) across stillbirth types, there appeared to be differences. For example, living in the most disadvantaged socio-economic quintile was a significant risk factor for antepartum (OR=2.0, 95% CI=1.1,3.7) and PROM (OR=2.4, 95% CI=1.0,5.6) stillbirth but not for SPON or MI stillbirth.

4) Conclusions:
Research into the factors that predict stillbirth at 20-23 weeks is of great importance to bereaved parents and can help guide prevention efforts.

Ethics statement
This research was granted ethics approval by the Western Australian Department of Health Human Research Ethics Committee (#2011/64) and the Western Australian Aboriginal Health Ethics Committee (#613). These ethical approvals support a waiver of consent on the basis that the study: (1) utilises routinely collected information from existing administrative datasets (and, accordingly, does not include active participants); and (2) only has access to de-identified data, which are stored, analysed and disseminated according to strict protocols.

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