Stillbirth means fourfold increased risk

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Women who have experienced a stillbirth have up to a fourfold increased risk of stillbirth in a second pregnancy compared to those who had an initial live birth, a new meta-analysis has found. Stillbirth rates have declined across most of Europe, but the UK still has a major public health problem. Ranked 33rd out of 35 for stillbirth rates among European countries, the UK recorded 3,286 stillborn babies in 2013.

“Stillbirth is one of the most common adverse obstetric outcomes and a traumatic experience for parents,” explain Sohinee Bhattacharya and colleagues from the University of Aberdeen, Scotland. “Couples who have experienced a stillbirth need to understand why it happened and want to know the risk for future pregnancies.” But there has not been sufficient information for the clinical management or to improve prevention of this traumatic outcome, they say. So they undertook systematic review and meta-analysis to examine the link between stillbirth in an initial pregnancy and risk of stillbirth in a subsequent pregnancy.

They analysed thirteen cohort and 3 case-control studies from high-income countries including Australia, Scotland, the US, Denmark, Israel, the Netherlands, Norway and Sweden. The definition of stillbirth was foetal death at more than 20 weeks’ gestation or a birth weight of at least 400g.

Data was collected for 3,412,079 women. Of these, 3,387,538 (99.3%) women had a previous live birth and 24,541 (0.7%) women had a stillbirth in an initial pregnancy. Stillbirths occurred in the subsequent pregnancy for 14,283 women: 606 of 24,541 (2.5%) in women with a history of stillbirth and 13,677 of 3,387,538 (0.4%) in women with no history.

Twelve studies assessed the risk of stillbirth in second pregnancies. Analyses showed that women who had a stillbirth in an initial pregnancy had a nearly fivefold increased risk of stillbirth in a second pregnancy. This risk is higher than stillbirth linked with medical conditions such as diabetes or hypertension.

After adjusting for confounding factors such as maternal age, maternal smoking and level of deprivation, the increased risk was up to fourfold higher. Risks following an unexplained stillbirth may not be increased because there are few studies and the evidence remains inadequate, explain the authors.

Pre-pregnancy counselling services should be provided to women who had a stillbirth, they urge, as well as advice on changing these lifestyle factors such as smoking and obesity that are both linked to an increased risk of stillbirth. Pregnancies should be closely monitored, and antenatal interventions and care be offered at the first sign of increased risk of distress or danger, they add.

 

In a linked editorial, experts from St Mary’s Hospital echo calls for additional care in next pregnancy, and for more research on unexplained stillbirths, which can account for around 20% of stillbirths. In addition, they stress the importance of an improved international classification system to determine causes of death, especially as these can be quite complex, so that interventions can be adequately targeted.

Abstract
Objective To determine the risk of recurrent stillbirth.
Design Systematic review and meta-analysis of cohort and case-control studies.
Data sources
Embase, Medline, Cochrane Library, PubMed, CINAHL, and Scopus searched systematically with no restrictions on date, publication, or language to identify relevant studies. Supplementary efforts included searching relevant internet resources as well as hand searching the reference lists of included studies. Where published information was unclear or inadequate, corresponding authors were contacted for more information.
Study selection
Cohort and case-control studies from high income countries were potentially eligible if they investigated the association between stillbirth in an initial pregnancy and risk of stillbirth in a subsequent pregnancy. Stillbirth was defined as foetal death occurring at more than 20 weeks’ gestation or a birth weight of at least 400 g. Two reviewers independently screened titles to identify eligible studies based on inclusion and exclusion criteria agreed a priori, extracted data, and assessed the methodological quality using scoring criteria from the critical appraisal skills programme. Random effects meta-analyses were used to combine the results of the included studies. Subgroup analysis was performed on studies that examined unexplained stillbirth.
Results
13 cohort studies and three case-control studies met the inclusion criteria and were included in the meta-analysis. Data were available on 3 412 079 women with pregnancies beyond 20 weeks duration, of who 3 387 538 (99.3%) had had a previous live birth and 24 541 (0.7%) a stillbirth. A total of 14 283 stillbirths occurred in subsequent pregnancies, 606/24 541 (2.5%) in women with a history of stillbirth and 13 677/3 387 538 (0.4%) among women with no such history (pooled odds ratio 4.83, 95% confidence interval 3.77 to 6.18). 12 studies specifically assessed the risk of stillbirth in second pregnancies. Compared with women who had a live birth in their first pregnancy, those who experienced a stillbirth were almost five times more likely to experience a stillbirth in their second pregnancy (odds ratio 4.77, 95% confidence interval 3.70 to 6.15). The pooled odds ratio using the adjusted effect measures from the primary studies was 3.38 (95% confidence interval 2.61 to 4.38). Four studies examined the risk of recurrent unexplained stillbirth. Methodological differences between these studies precluded pooling the results.
Conclusions
The risk of stillbirth in subsequent pregnancies is higher in women who experience a stillbirth in their first pregnancy. This increased risk remained after adjusted analysis. Evidence surrounding the recurrence risk of unexplained stillbirth remains controversial.

BMJ material
BMJ full study
BMJ editorial


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