Abstract
Supine maternal position in the third trimester is associated with reduced uterine blood flow and increased risk of late stillbirth. As reduced uterine blood flow is also associated with fetal growth restriction, this study explored the association between the position in which pregnant women went to sleep and infant birth weight. To examine the association between supine position when going to sleep in women after 28 weeks of pregnancy and lower birth weight and birth weight centiles. Prespecified subgroup analysis using data from controls in an individual participant data meta-analysis of 4 case-control studies investigating sleep and stillbirth in New Zealand, Australia, and the United Kingdom. Participants were women with ongoing pregnancies at 28 weeks' gestation or more at interview. The primary outcome was adjusted mean difference (aMD) in birth weight. Secondary outcomes were birth weight centiles (INTERGROWTH-21st and customized) and adjusted odds ratios (aORs) for birth weight less than 50th and less than 10th centile (small for gestational age) for supine vs nonsupine going-to-sleep position in the last 1 to 4 weeks, adjusted for variables known to be associated with birth size. Of 1760 women (mean [SD] age, 30.25 [5.46] years), 57 (3.2%) reported they usually went to sleep supine during the previous 1 to 4 weeks. Adjusted mean (SE) birth weight was 3410 (112) g among women who reported supine position and 3554 (98) g among women who reported nonsupine position (aMD, 144 g; 95% CI, -253 to -36 g; P = .009), representing an approximate 10-percentile reduction in adjusted mean INTERGROWTH-21st (48.5 vs 58.6; aMD, -10.1; 95% CI, -17.1 to -3.1) and customized (40.7 vs 49.7; aMD, -9.0; 95% CI, -16.6 to -1.4) centiles. There was a nonsignificant increase in birth weight at less than the 50th INTERGROWTH-21st centile (aOR, 1.90; 95% CI, 0.83-4.34) and a 2-fold increase in birth weight at less than the 50th customized centile (aOR, 2.12; 95% CI, 1.20-3.76). Going to sleep supine was associated with a 3-fold increase in small for gestational age birth weight by INTERGROWTH-21st standards (aOR, 3.23; 95% CI, 1.37-7.59) and a nonsignificant increase in small for gestational age birth weight customized standards (aOR, 1.63; 95% CI, 0.77-3.44). This study found that going to sleep in a supine position in late pregnancy was independently associated with reduced birth weight and birth weight centile. This novel association is biologically plausible and likely modifiable. Public health campaigns that encourage women in the third trimester of pregnancy to settle to sleep on their side have potential to optimize birth weight.
Highlights
Maternal supine position in late pregnancy is associated with significant hemodynamic changes that can result in a reduction in blood flow to the fetus.[1]
There was a nonsignificant increase in birth weight at less than the 50th INTERGROWTH-21st centile and a 2-fold increase in birth weight at less than the 50th customized centile
Going to sleep supine was associated with a 3-fold increase in small for gestational age birth weight by INTERGROWTH-21st standards and a nonsignificant increase in small for gestational age birth weight customized standards
Summary
Maternal supine position in late pregnancy is associated with significant hemodynamic changes that can result in a reduction in blood flow to the fetus.[1] Supine maternal going-to-sleep position has recently been found to confer an independent 2.6-fold (adjusted odds ratio [aOR], 2.63; 95% CI, 1.724.04) increased risk of late (Ն28 weeks’ gestation) stillbirth.[2,3,4,5,6] Maternal effects of a supine position in late pregnancy include compression of the inferior vena cava[1,7] and aorta[1,8] leading to a reduction in maternal cardiac output,[1,7,9] a reduction in uterine artery blood flow,[10] and decreased placental perfusion.[11] Fetal effects associated with supine maternal position include a redistribution of blood circulation with increased flow through the fetal middle cerebral artery[12,13] and increased fetal quiescence,[14] suggesting fetal adaptation to mild hypoxic stress. Given that impaired utero-placental flow is associated with fetal growth restriction,[15] it is plausible that repeated exposure to supine maternal position during sleep in late pregnancy may adversely affect fetal growth. The initial going-to-sleep position is the sleep position that women maintain for the longest duration throughout the night[16]; going-to-sleep position is likely to have the greatest impact on blood flow to the developing fetus
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.