RESUMO
OBJECTIVES: To compare vaginal with intramuscular progesterone administration to prevent preterm labor in women with singleton pregnancies and at increased risk of preterm birth. STUDY DESIGN: Prospective comparative clinical trial. POPULATION: One hundred and sixty pregnant women at 20-24 weeks gestation at the risk of preterm labor were classified into: 80 women who received micronized progesterone tablets 200 mg vaginally daily (Group A) and 80 women who received 100 mg progesterone in the form of intramuscular every third day (Group B). METHODS: Estimation of gestational age, assessment of fetal growth and fetal biophysical profile by trans-abdominal ultrasonographic examination was done every 4 weeks till delivery. Measurement of cervical length was achieved by transvaginal ultrasonography, done every 4 weeks till delivery. MAIN OUTCOME MEASURES: Incidence of preterm delivery, mean gestational age and the incidence of adverse events of intramuscular versus vaginal route of progesterone administration. RESULTS: The incidence of preterm delivery in Group A was 20% and in Group B was 27.5%. The difference between both groups was statistically insignificant. In addition, the rate of adverse events reported in women received injectable progesterone was significantly higher than the rate of adverse events reported in women who received vaginal progesterone therapy. CONCLUSION: Vaginally administrated progesterone was nearly as equally effective as intramuscular progesterone in the prevention of preterm labor in women at risk and in the meantime has less undesirable events.