Epidemiologic risk factors for preterm delivery

Background: Prematurity remains the most significant cause of neonatal morbidity and mortality. Knowing which group of women is at risk for developing preterm labor will define a target population for better prenatal care and prevention modalities. Objective: To examine whether preterm delivery rates are associated with ethnicity, age, parity, and style of living. Methods: We conducted a longitudinal case series examining obstetric and demographic data of 17,493 deliveries that occurred between June 1994 and May 1999. All deliveries were performed in the obstetric department of HaEmek Medical Center (Afula, Israel), which serves as a referral center. The main outcome measures were preterm delivery, as related to the women's ethnicity, age parity, and style of living - namely, town, village, or kibbutz. Results: The overall preterm delivery rate was 8.5%. The preterm delivery rate in non-Jewish women (10.5%) was higher than in Jewish women (7.1%) (P < 0.00001). The preterm delivery rate in women younger than 20 or older than 40 (12.5%) was much higher than in women between the ages of 21 and 40 (8.0%) (P < 0.00001). Grand-multipara women (>8) had a higher preterm delivery rate (13.8%) than less parous women (8.5%) (P < 0.012). Style of living was also associated with the preterm delivery rate (P < 0.00001): kibbutz 5.5%, Jewish towns 7.8%, non-Jewish towns 8.7%, Jewish villages 6.7%, and non-Jewish villages 11.0%. Conclusions: Style of living, ethnicity, age and parity are statistically significant risk factors for preterm delivery in our area. These factors provide a more definable target population for better prenatal care.