Objectively assessed sleep-disordered breathing during pregnancy and infant birthweight.

Background: Sleep-disordered breathing (SDB) in pregnancy is associated with adverse maternal outcomes. The relationship between SDB and infant birthweight is unclear. This study's primary aim is to determine if objectively measured SDB in pregnancy is associated with infant birthweight.

Methods: We measured SDB objectively in early (6-15 weeks' gestation) and mid (22-31 weeks' gestation) pregnancy in a large cohort of nulliparous women. SDB was defined as an Apnea-Hypopnea Index ≥5 and in secondary analyses we also examined measures of nocturnal hypoxemia. We used a modified Poisson regression approach to estimate relative risks (RR) of large-for-gestational-age (LGA: >90th percentile for gestational age) and small-for-gestational-age (SGA: <10th percentile for gestational age) birthweights.

Results: The prevalence of early-pregnancy SDB was nearly 4%. The incidence of mid-pregnancy SDB was nearly 6.0%. The prevalence of LGA and SGA was 7.4% and 11.9%, respectively. Early-pregnancy SDB was associated with a higher risk of LGA in unadjusted models (RR 2.2, 95% CI 1.3-3.5) but not BMI-adjusted models (aRR 1.0, 95% CI 0.6-1.8). Mid-pregnancy SDB was not associated with SGA or LGA. Mid-pregnancy nocturnal hypoxemia (% of sleep time <90% oxygen saturation) and increasing nocturnal hypoxemia from early to mid-pregnancy were associated with a higher risk of LGA in BMI-adjusted models. SDB and nocturnal hypoxemia were not associated with SGA.

Conclusions: SDB in pregnancy was not associated with an increased risk of LGA or SGA birthweight, independent of BMI. Some measures nocturnal hypoxemia were associated with an increase in LGA risk, independent of BMI. ClinicalTrials.gov Registration number NCT02231398.