Objective: To identify risk factors for recurrent preterm delivery among primiparous women with previous preterm delivery.
Study design: A retrospective case-control study was designed: 152 primiparous women who delivered preterm (22-36 weeks) were divided into two groups: 81 had a second preterm delivery (study group) and 71 had a second-term delivery (control group). Exclusion criteria were induced preterm delivery, hydramnions and multiple gestations.
Results: Comparing second preterm delivery before 34 weeks (n = 36) to the second delivery of the control group, higher rates of hospitalization due to preterm labor were noted in the study versus the control group (52.8% versus 16.9%,P = 0.001). The interval between pregnancies was shorter in the study subgroup, before 34 weeks gestational age, versus the controls (20.1 +/-15.7 months versus 28.9 +/- 18.7 months, P = 0.011). Multiple regression analyses, adjusted for confounding variables, found the occurrence of preterm labor and short interval between pregnancies, especially up to 12 months, as independent risk factors for the recurrence of preterm delivery (OR = 4.98; P , 0.001; OR = 5.13; P = 0.007, respectively).
Conclusion: When adjusted for confounding variables, short interval between pregnancies is an independent risk factor for recurrent preterm delivery.