Objectively Measured Maternal Supine Sleep and Fetal Growth: A Prospective Cohort Study.

Area of Science:

• Obstetrics and Gynecology
• Perinatal Health
• Sleep Medicine

Background:

• Supine sleep position in late pregnancy is a potential risk factor for stillbirth.
• Objective measurement of sleep position is crucial for accurate risk assessment.
• Existing research often relies on self-reported sleep positions, which can be inaccurate.

Purpose of the Study:

• To investigate the relationship between different definitions of objectively measured supine sleep position during late pregnancy and customized birthweight centiles.
• To assess supine sleep position as a marker of fetal wellbeing.
• To explore potential risk indices related to supine sleep duration.

Main Methods:

• Prospective cohort study involving 84 pregnant women (32-36 weeks gestation) in an Australian public hospital antenatal clinic.
• Body position measured using a tri-axial accelerometer for seven nights, defining 'broad supine' (0-45° tilt) and 'supine low-tilt' (0-15°).
• Birthweights analyzed using customized centiles (GROW software); primary outcome was customized birthweight centile.

Main Results:

• Median nightly duration of broad supine positioning was 65.9 minutes, compared to 9.1 minutes for supine low-tilt.
• No significant relationship was found between customized birthweight centile and time spent in broad supine or supine low-tilt.
• No association observed between supine risk indices and customized birthweight centile, birthweight, gestational age, or fetal growth trajectory.

Conclusions:

• No evidence of an association between objectively measured supine sleep and customized birthweight centile in this cohort.
• Mechanisms other than fetal growth may link supine sleep position to late stillbirth risk.
• Further prospective studies are needed to clarify the cause-and-effect relationship, though feasibility may be limited by low stillbirth rates.