Although a large number of studies have examined risk factors for stillbirth, few have explored a wide range of potential risk factors. Although little is known about the potential impact of sleep practices on the developing fetus, some studies have reported that sleeping supine may be associated with sleep-disordered breathing and lower maternal cardiac output in late pregnancy. The Auckland Stillbirth Study was a prospective population-based case-control study with the broad aim to identify modifiable risk factors for late stillbirth (≥28 weeks' gestation). The present study explored the possibility that snoring, sleep position, and other sleep practices in pregnant women were associated with risk of late stillbirth. Participants were 155 singleton women with a late stillbirth (≥28 weeks' gestation); matched controls were singleton women with ongoing pregnancies at the same gestational age as the stillbirths. Multivariable analysis adjusted for potential confounding factors. The primary study outcome measures were self-reported maternal snoring, daytime sleepiness (determined also with the Epworth sleepiness scale), and maternal sleep position both at the time of going to sleep and on waking (classified as left side, right side, back, and other). The prevalence of late stillbirth among the cohort was 3.09/1000 births. No association was found between risk of late stillbirth and either maternal snoring or daytime sleepiness. After adjustment for multiple potential confounding factors, the risk of late stillbirth was increased among women who slept on their back or their right side on the previous night compared with those who slept on their left side; the adjusted odds ratio (aOR) for back sleeping was 2.54, with a 95% confidence interval (CI) of 1.04-6.18, and for right side sleeping was 1.74, with a 95% CI of 0.98–3.01. The absolute risk of late stillbirth for women who went to sleep on their left side was half of those who did not go to sleep on their left (1.96/1000 vs. 3.93/1000). The risk of a late stillbirth was also lower in women who got up to go to the toilet once or less on the last night compared with those who got up more frequently (aOR, 2.28; 95% CI, 1.40–3.71). There was a higher likelihood for late stillbirth among women sleeping regularly during the day in the previous month in comparison with those who did not (aOR, 2.04; 95% CI, 1.26–3.27). These findings suggest that the risk of late stillbirth may be lower in pregnant women who sleep on their left side. This novel association requires confirmation before any recommendations can be made on optimal sleep position in late pregnancy.