- OBJECTIVE: To compare epidemiological and obstetric characteristics, etiology and next pregnancy outcomes of women with primary vs. secondary recurrent pregnancy loss (RPL). STUDY DESIGN: A retrospective cohort study, including 420 patients with two or more consecutive pregnancy losses followed by a subsequent (index) pregnancy, of whom 162 were primary RPL women and 258 were secondary RPL women. All patients were evaluated and treated in the RPL clinic at the Soroka University Medical Center. RESULTS: Live birth rate in the index pregnancy was not statistically different between primary and secondary RPL women (75.9 and 70.9%, respectively). The only significant difference in the etiology evaluation was in abnormal prolactin levels (14.1% of the primary and 1.4% of the secondary RPL group). Women with primary RPL had, at the index pregnancy, significantly higher rates of preterm delivery, fetal growth restriction, and gestational diabetes mellitus. In a multivariable logistic regression analysis, primary RPL adjusted for maternal age and gravidity, was an independent risk factor for preterm delivery compared with secondary RPL [adjusted OR 2.62, CI (95%) 1.30-5.26]. CONCLUSIONS: The prognosis of the two groups was similar regarding live birth rate at the index pregnancy; however, women with primary RPL were more prone to adverse obstetric and neonatal outcomes.