Activity restriction and risk of adverse pregnancy outcomes.

Background: Activity restriction is a common recommendation given to patients during pregnancy for various indications, despite lack of definitive data showing improvements in pregnancy outcomes.
Objective: To determine if activity restriction (AR) in pregnancy is associated with decreased odds of adverse pregnancy outcomes (APOs).
Study Design: Secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) prospective cohort. Nulliparous singletons were followed at 8 sites from October 2010-September 2013. Demographic and clinical data were collected at 4 timepoints, and participants were surveyed about AR recommendations at 22w0d-29w6d and delivery. We excluded participants missing data on AR and age. Participants were grouped according to history of AR, and APOs included: gestational hypertension (gHTN), preeclampsia/eclampsia, preterm birth (PTB), and small for gestational age (SGA) neonate. Associations between AR and APOs were examined using uni- and multivariable logistic regression models adjusting for a priori identified APO risk factors.
Results: Of 10,038 nuMoM2b participants, 9,312 met inclusion criteria and 1,386 (14.9%) were recommended AR; participants identifying as Black (aOR 0.81 [95% CI 0.68-0.98]) or Hispanic (aOR 0.73 [95% CI 0.61-0.87]) were less likely to be placed on AR when compared to those identifying as White. Overall, 3,197 (34.3%) experienced at least one APO (717 [51.7%] of participants with AR compared to 2,480 [31.3%] participants without AR). After adjustment for baseline differences, the AR group had increased odds of gHTN (aOR 1.61 [95% CI 1.35-1.92]), preeclampsia/eclampsia (aOR 2.52 [95% CI 2.06-3.09]) and iatrogenic and spontaneous PTB (aOR 2.98 [95% CI 2.41-3.69]), but not delivery of an SGA neonate.
Conclusion: AR in pregnancy was independently associated with increased odds of hypertensive disorders of pregnancy and PTB, but future prospective work is needed to determine potential causality. Further, participants identifying as Black or Hispanic were significantly less likely to be recommended AR compared to those identifying as White. While AR is not an evidence-based practice, these findings suggest bias may impact which patients receive advice to limit activity in pregnancy.
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