Moderate and increased physical activity is not detrimental to live birth rates among women with unexplained infertility and obesity

OBJECTIVE: To determine if moderate physical activity is associated with live birth rates in women with unexplained infertility and obesity. DESIGN: Secondary analysis of the Improving Reproductive Fitness through Pretreatment with Lifestyle Modification in Obese Women with Unexplained Infertility trial. SETTING: US fertility centers, 2015–2019. PATIENT(S): A total of 379 women participated in Improving Reproductive Fitness through Pretreatment with Lifestyle Modification in Obese Women with Unexplained Infertility trial, a lifestyle modification program with increased physical activity (phase I, 16 weeks) and up to three cycles of clomiphene citrate treatment and intrauterine insemination (phase II). INTERVENTION(S): Participants were instructed to add 500 steps/day weekly until a maximum of 10,000 steps/day was reached and maintained. Participants were stratified as active (top third, N = 125) and less active (lower third, N = 125) on the basis of the average number of steps per day recorded using a FitBit activity tracker. MAIN OUTCOME MEASURE(S): Live birth rate. RESULT(S): Active participants were more physically active at the time of enrollment than less active participants (average baseline steps per day, 8,708 [7,079–10,000] vs. 4,695 [3,844–5,811]; P ≤ 0.001) and were more likely to reach 10,000 steps/day than less active participants (average steps per day, 10,526 [9,481–11,810] vs. 6,442 [4,644–7,747]; P ≤ 0.001), although both groups increased their average steps per day by a similar amount (1,818 vs.1,747; P = 0.57). There was no difference in live birth rates (24/125 [19.2%] vs. 25/125 [20%]; P = 0.87) between active and less active participants nor were there differences in clinical pregnancy rates (P = 0.45) or miscarriage rates (P = 0.49) between the two groups. CONCLUSION(S): Active participants were more likely to achieve the physical activity goal, although this was not associated with benefit or harm with respect to live birth. CLINICAL TRIAL REGISTRATION NUMBER: ClinicalTrials.gov (NCT02432209), first posted: May 4, 2015.