Ethnic variation in stillbirth risk and the role of maternal obesity: analysis of routine data from a London maternity unit

Abstract

BackgroundApproximately 5 in 1,000 deliveries in England and Wales result in stillbirth, with little improvement in figures over the last few decades. The aim of this study was to investigate the association between clinical and socio-demographic factors and stillbirth, with a particular focus on ethnicity and obesity.MethodsAnalysis of routine maternity data on 53,293 singleton births occurring in a large London teaching hospital between 2004 and 2012. Logistic regression was used to investigate risk factors for stillbirth and to explore potential effect modification.Results53,293 deliveries occurred during the time period, of which 329 resulted in a stillbirth (6.2 per 1,000 births). Compared to White women, non-White ethnicity was associated with a doubling of the odds of stillbirth (aOR for Black women 2.15, 95% CI 1.56-2.97; aOR for South Asian women 2.33, 95% CI 1.42-3.83). Obese women had a trend towards higher odds of stillbirth compared to women of recommended BMI (aOR 1.38, 95% CI 0.98-1.96), though this was not significant (p 0.07). Both higher parity (≥2 compared to para 1) and hypertension were associated with a higher odds of stillbirth (parity ≥2 aOR 1.65, 95% CI 1.13-2.39; hypertension aOR 1.84, 95% CI 1.22-2.78) but there was no evidence that area deprivation or maternal age were independently associated with stillbirth in this population. There was some evidence of effect modification between ethnicity and obesity (p value for interaction 0.06), with obesity a particularly strong risk factor for stillbirth in South Asian women (aOR 4.64, 95% CI 1.84-11.70).ConclusionsThere was a high prevalence of stillbirth in this multi-ethnic urban population. The increased risk of stillbirth observed in non-White women remains after adjusting for other factors. Our finding of possible effect modification between ethnicity and obesity suggests that further research should be conducted in order to improve understanding of the interplay between ethnicity, obesity and stillbirth.Electronic supplementary materialThe online version of this article (doi:10.1186/s12884-014-0404-0) contains supplementary material, which is available to authorized users.

Effects of maternal anthropometrics on pregnancy outcomes in South Asian women: a systematic review

“…Thirteen studies were from the UK (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39), three from Australia (40,41), two from Norway (42,43) and Canada (44,45), and one from USA (46) and Spain (47) ( Table 1). Some studies used more than one exposure: 21 studies used maternal anthropometric measurements as the exposure (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(43)(44)(45)(46)(47)(48) (group 1), three used gestational change in maternal anthropometrics as the exposure (31,42,47) (group 2) and two used a combination of pre-pregnancy anthropometrics and gestational change in anthropometrics (42, 43) (group 3). Of the studies that used maternal BMI as a categorical exposure (n = 7), only three studies applied BMI criteria for South Asian populations (29,46,48).…”

“…Some studies used more than one exposure: 21 studies used maternal anthropometric measurements as the exposure (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(43)(44)(45)(46)(47)(48) (group 1), three used gestational change in maternal anthropometrics as the exposure (31,42,47) (group 2) and two used a combination of pre-pregnancy anthropometrics and gestational change in anthropometrics (42, 43) (group 3). Of the studies that used maternal BMI as a categorical exposure (n = 7), only three studies applied BMI criteria for South Asian populations (29,46,48). The quality scores of the studies ranged from 2 to 7 (out of a maximum of 8), with a mean score of 5 ( Table 1).…”

“…We also searched citations and reference lists of included studies, and the reference lists of reviews that were related to the topic area. Of the 22 included studies, 20 were identified through database search alone (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(42)(43)(44)(45)(46)48), one from screening the reference lists of relevant reviews (41) and one from searching the citations of included studies (47). In their recent review and meta-analysis, Heslehurst et al also found that in order to minimize bias, it was essential to include evidence from searches in addition to database searching (7).…”

“…The other two studies both found a change in odds compared with the higher BMI cut-off. Penn et al found that the odds of stillbirth decreased from 4.64 (1.84, 11.70) for BMI ≥ 30 kg m À2 to 2.83 (1.17, 6.85) for BMI ≥ 27.5 kg m À2 (29). Despite the decrease in odds, South Asian women still had higher odds of stillbirth than do White women: 1.32 (0.68, 2.57) (29).…”

“…Exposure: maternal pre-pregnancy anthropometrics A significant positive association was identified between maternal BMI and stillbirth for South Asian infants but not for White infants in one study (29); the other study found a higher OR of stillbirth associated with maternal BMI for South Asian infants than for White (although this did not reach statistical significance) (48). Two studies found a significant positive association between maternal BMI and hypertensive disorders of pregnancy for both White and South Asian women, which was lower in South Asian women (28,48); this association remained following adjustment in one of the studies (48).…”