 We randomized 120 women with singleton pregnancy who were successfully treated for threatened preterm labor before 34 completed weeks to receive either maintenance tocolysis with two 40 mg ritodrine sustained release capsules three times a day study group, n62 or no treatment control group, n58 for three days. The primary outcome measure was the recurrent episode of threatened preterm labor within 72 hours, which was defined as regular palpable uterine contractions and change in cervical effacement andor cervical dilatation on clinical examination. Secondary outcome measures included the incidence of preterm birth, neonatal adverse outcomes, and maternal side effects. 