Determinants of late stillbirth Auckland 2006-2009

Abstract

Stillbirth is a devastating and too common outcome of pregnancy; globally there are approximately three million deaths after 28 weeks‟ gestation every year. In New Zealand, as in other high income countries, more than 1 in 200 babies die before birth, and around 1 in 300 die in the last three months of pregnancy. During the mid twentieth century there was a dramatic decline in the rate of stillbirth, however this improvement has not been sustained in recent years. Previous studies have identified certain causes and risk factors for late stillbirth, but over a third of the deaths remain unexplained. The current variation in the rate of stillbirths both across and within high income countries suggests that it is possible to make further improvements in stillbirth rates. We hypothesised that there would be modifiable, but as yet unidentified risk factors for late stillbirth. The Auckland Stillbirth Study was the first case control study to select women with ongoing pregnancies as gestation matched controls. This study found that the disparity in rates of late stillbirth in women from different ethnicities in New Zealand could be attributed to associated factors such as high parity, high body mass index and social deprivation. Regular utilisation of antenatal care was found to be protective, and women who attended at least 50% of recommended antenatal visits had a lower risk of stillbirth compared to those who did not. Antenatal identification of sub-optimal fetal growth was found to be a possible aspect of the benefit of regular antenatal attendance. Maternal perception of fetal movements was also identified as an area of importance, with women who perceived their baby‟s movements to decrease in the last two weeks of the pregnancy being at greater risk of experiencing a stillbirth. In addition this study found an association between maternal sleep practices and risk of late stillbirth. Most strikingly, the study found that women who went to sleep on their left side on the last night (prior to stillbirth/interview) were half as likely to experience a late stillbirth compared to women who went to sleep in any other position. This study has added a New Zealand perspective to the existing literature on certain known risk factors for late stillbirth (such as high body mass index). It has also identified novel factors that present new possibilities for further research and for the potential for future reductions in the incidence of late stillbirth.