BACKGROUND AND PURPOSE:

• Stillbirth rates are 1.7-8.8 per 1,000 births > 28 weeks in high-income countries with significant variation related to economic factors and population characteristics such as ethnicity and race
• Variation suggests that there may be modifiable risk factors unlike age that can be altered
• The Auckland Stillbirth Study and other studies demonstrated an association between a supine going-to-sleep position and late stillbirth risk
• Data limited due to study size, recall bias and adjustment for confounders
• Heasell et al. (BJOG, 2017) sought to determine the association between maternal sleep practices and risk of stillbirth

METHODS:

• Prospective case-control study (2014-2016)
• Midlands and North of England Stillbirth Study (MiNESS) was conducted in 41 maternity units in the UK
• Cases: Women who had a stillbirth after ≥ 28 weeks’ gestation and no known congenital anomalies
  • Interviews were conducted as close to the time of stillbirth as possible with an aim of being completed 1–6 weeks after the birth
• Controls: Women with ongoing pregnancy (2:1 ratio to cases)
  • Women who had a stillbirth or child with an anomaly were excluded from the analysis
  • Randomly given a gestational age for the interview so that there would be a similar gestational age distribution compared to the late stillbirths in that particular hospital
• Going-to-sleep position was classified as left side, supine, right side, tummy, variable side, propped up, or unknown
• Primary outcome
  • Odds of late stillbirth associated with self-reported maternal going-to-sleep position on the night prior to stillbirth for cases and the night before the interview for controls
• Other questions
  • Sleeping position in the last 4 weeks before the stillbirth and prior to pregnancy
  • Duration of sleep, frequency of getting up to go to the toilet during the last night, and daytime napping in the last four weeks

RESULTS:

• 291 women with a previous stillbirth and 733 with a live-born baby were interviewed
• Supine going-to-sleep position the night before stillbirth had a 2.3-fold increased risk of late stillbirth (adjusted Odds Ratio [aOR] 2.31, 95% CI 1.04–5.11) compared to having gone to sleep on the left side
• There was no significant difference in sleep position in the preceding four weeks or prior to pregnancy between cases and controls
• Women who slept < 5.5 hours or ≥ 9.5 hours were more likely to have a stillbirth
• Women who were got up to use the toilet once or less the night before stillbirth were more likely to have a stillbirth (aOR 2.81, 95% CI 1.85–4.26)
• Women who took a daytime nap every day was also more likely to have a still birth (aOR 2.22, 95% CI 1.26–3.94)
• Findings were independent of gestational age, the presence of an SGA fetus, obesity, education level, parity, and maternal smoking status

CONCLUSION:

• Supine going-to-sleep position is associated with 2.3x increased risk of stillbirth after 28 weeks’ gestation
• The results in this study suggest that 3.7% of stillbirths > 28 weeks may be related to the supine sleep position
• Programs have already begun in New Zealand to encourage women not to sleep on their back
  • A fall in late stillbirth in New Zealand in the last five years may be due to documented changes in maternal going-to-sleep position
• The authors conclude that it would take over 1 million women to demonstrate differences in an interventional trial and based on these results and consistency with previous studies, “it is timely to evaluate whether going-to-sleep position can be modified, and how this can best be achieved”.

Learn More – Primary Sources:

Association between maternal sleep practices and late stillbirth – findings from a stillbirth case-control study