Preterm birth remains a leading cause of perinatal morbidity and mortality, and prophylactic and therapeutic strategies have not reduced its frequency. Activity restriction specifically has not been beneficial and is associated with adverse social, economic, and health outcomes. This present secondary analysis of data from the Short Cervix and Nulliparity Trial was designed to estimate the determinants and outcomes of activity restriction in parturients with a short cervix.
In the original randomized placebo-controlled trial, asymptomatic nulliparous women with singleton gestations and cervices of less than 30 mm received either weekly intramuscular 17-α hydroxyprogesterone caproate or placebo. During the weekly study visits, participants were asked whether pelvic rest (no sexual activity), reduction of work activity, or reduction of nonwork activity had been recommended. Women who had reductions in either pelvic, work, or nonwork activity were considered as having had “any” activity restriction. The association between activity restriction and preterm birth was determined at less than 37 and less than 34 weeks’ gestation. Multivariable analyses were performed with multiple logistic regression with odds ratios (ORs), adjusted ORs (aORs), and 95% confidence intervals (CIs) reported. All tests were 2 tailed, and P < 0.05 defined statistical significance. All analyses were performed with SAS version 9.2.
Of the 657 women in the randomized trial, 646 (98%) responded to questions regarding activity restriction. Nearly 40% of women with a short cervix were placed on some activity restriction, usually in the midsecond to early third trimester, soon after the diagnosis of a short cervix was made. In 171 (68%) of 252 patients, all 3 types of activity restriction were combined. Compared with women without activity restriction, women who received recommendations for activity restriction were older (P < 0.001), more likely to have private insurance (P = 0.01), and less likely to be Hispanic white (P < 0.001); they also had shorter cervical lengths and were more likely to have cervical funneling or intra-amniotic debris. Preterm birth at less than 37 weeks’ gestation was significantly more common among women placed on any activity restriction (37% vs 17%, P < 0.001; OR, 2.91; 95% CI, 2.0–4.21). No significant interactions were found between activity restriction and treatment with 17-α hydroxyprogesterone caproate, cervical length of less than 15 mm, or gestational age at screening. After controlling for treatment group and demographic and ultrasonographic differences among those with and without activity restriction, preterm birth at less than 37 or less than 34 weeks’ gestation remained significantly more common among those placed on any activity restriction (aOR, 2.37; 95% CI 1.60–3.53 and aOR, 2.28, 95% CI, 1.36–3.80, respectively). Results were similar when only women prescribed limitation of work and nonwork activities were included in the restriction group (<37 weeks’ gestation: aOR, 2.44; 95% CI, 1.63–3.65; <34 weeks gestation: aOR, 2.70; 95% CI, 1.62–4.52).
Some form of activity restriction was prescribed for more than 1 in every 3 nulliparous women with a short cervix. Activity restriction affected patients’ work and home life, and yet, they were still significantly more likely to deliver preterm. Activity restriction has been associated with increased stress and anxiety and increased chances of venous thromboembolism, bone loss, deconditioning, and financial difficulties. These complications and risk of preterm birth suggest that this intervention should be proven beneficial before it is used routinely for preterm birth prophylaxis.