Randomized trial of advice from healthcare professionals to eliminate constriction by maternal clothing on the trunk to prevent preterm birth and improve health status.

Aim: Women's clothing during pregnancy may influence perinatal outcomes. A preliminary study suggested that midwives' advice to avoid wearing tight clothing during pregnancy may reduce the risk of preterm delivery. We examined the effects of such advice to pregnant women on the risk of preterm birth and health status during pregnancy.

Methods: An open-label evaluator-blinded randomized controlled trial was conducted at the National Centre for Child Health and Development in Tokyo, Japan. Normal pregnant women were randomly assigned to receive constrictive clothing elimination care or standard care at 20 weeks gestation. The control group was issued leaflets concerning anemia prevention at entry and skin care at 30 weeks' gestation, along with a brief explanation and answers to questions by midwives as standard care. The intervention group received advice from midwives concerning avoiding constrictive clothing in addition to standard care. The primary outcome was the incidence of preterm birth (<37 weeks). The secondary outcomes were 12 indicators related to preterm delivery or health status.

Results: Among 624 randomly assigned women, 599 (intervention group, n = 306; control group, n = 293) completed the study between February 2015 and August 2016. The incidence of preterm birth in the intervention and control groups was 4.2% (13/306) and 5.1% (15/293), respectively (p = 0.614). There were no significant differences regarding any secondary outcomes, including obstetric outcomes and physical/mental indicators, during pregnancy.

Conclusions: Advice from midwives to avoid constrictive clothing during pregnancy did not influence the incidence of preterm birth or maternal health status.

Trial Registration: UMIN000016853 (March 30, 2015).