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33: Prior preterm birth in first pregnancy and risk of small-for-gestational-age birth in second pregnancy: a population-based study

      Objective

      To evaluate risk of small-for-gestational-age birth in the second pregnancy following preterm delivery in first pregnancy

      Study Design

      We conducted a population-based retrospective cohort study using birth certificate data from the Missouri maternally linked cohort from 1989 to 2005. The study sample included Caucasian and African American women who delivered their first 2 non-anomalous, vertex, singleton pregnancies between 20 and 44 weeks of gestation without chronic hypertension, preeclampsia, renal disease, or diabetes mellitus in both pregnancies (n=197,556). Multivariable logistic regression models were fit to estimate odds ratios and 95% confidence intervals for risk of small-for-gestational-age birth (SGA) in second pregnancy by gestational age in the first preterm births. Infants were classified as SGA <5 and <10 percentile (%tile according to a population-based birth weight reference).

      Results

      Among women with a full-term 2nd pregnancy, those who delivered their 1st pregnancy at ≤28 weeks, 29 to 32 weeks, and 33 to 36 weeks of gestation had increased odds of <10%tile SGA in 2nd pregnancy by 71%, 90%, and 69%, respectively, after controlling for pregnancy interval, maternal age, race, pre-pregnancy BMI, cigarette use during pregnancy, and Medicaid status. Similarly, among women with a term 2nd pregnancy, those who delivered their 1st pregnancy at ≤28 weeks, 29 to 32 weeks, and 33 to 36 weeks of gestation had increased odds of <5%tile SGA in 2nd pregnancy by 126%, 106%, and 81%, respectively, after controlling for confounders. No significant increased risk of either <5 or <10%tile SGA in 2nd pregnancy was observed among women with recurrent preterm delivery. Conclusion: Prior preterm delivery is associated with increased odds of SGA births despite an uncomplicated term second pregnancy.

      Conclusion

      Prior preterm delivery is associated with increased odds of SGA births despite an uncomplicated term second pregnancy.
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