Evaluation of the Effect of Low Dose Aspirin on Cervical Length as an Indicator of Preterm Labor in Nulliparous Women

Preterm labor is one of the most common midwifery problems in developing and even advanced countries imposing a huge cost on people and the health system. One of the most important causes of preterm labor is short cervical length. Periodic monitoring of cervical length is an important factor in predicting incidence of preterm labor. The purpose of this study was to determine the effect of low dose aspirin on cervical length in nulliparous women. In a double-blind randomized clinical trial, nulliparous pregnant women with gestational age of less than 13 weeks and 6 days were enrolled in the study and randomly divided into intervention and control groups. Demographic, clinical and Para clinical data were recorded. The intervention group received 80 mg daily aspirin, while the control group received placebo. Cervical length and maternal and fetal outcomes were recorded and analyzed. The results have shown a decrease in cervical length at 12, 18 and 30 weeks of gestation in the control group and an increase in the intervention group, indicating the effect of aspirin administration on prevention of preterm labor (P <0.05). Maternal complications were not significantly different between the two groups. Cervical length with cut-off point of 30 at 30 weeks’ gestation had a positive predictive value of 64% and a negative predictive value of 94% in predicting preterm labor. Our study has shown that low-dose aspirin administration may prevent cervical length reduction and preterm labor, although it has had no effect on reducing maternal complications such as preeclampsia, vaginal bleeding, low birth weight, and spontaneous abortion. Moreover, measurement of cervical length (with cut-off point of 30 mm) in the third trimester of pregnancy is a good indicator in predicting preterm labor.