Preterm delivery and low birth weight in singleton pregnancies conceived by women with and without a history of infertility.

To determine predictors of low birth weight (LBW) and preterm delivery (PTD) in singleton pregnancies conceived by women with and without a history of infertility. Retrospective cohort study. Eleven infertility clinics in northern California. Three groups of women who carried singleton pregnancies to ≥20 weeks' gestation: 542 infertile women who conceived after treatment, 441 infertile women who conceived spontaneously, and 1,008 fertile women for comparison. Chart review. Association of LBW or PTD with infertility treatment, maternal age, parity, obesity, or development of gestational diabetes. Infertile women who conceived with treatment were more likely to be obese, develop gestational diabetes, and have ovarian, ovulatory, or male factor infertility than infertile women who conceived spontaneously. Infertile women who conceived after treatment had 1.61 times greater odds of having an LBW infant. Nulliparity was an independent predictor of LBW and PTD in all three groups after controlling for maternal age, history of infertility, infertility treatment, obesity, and gestational diabetes. Nulliparous women and women with a history of infertility who conceive a singleton after treatment may be at increased odds for having an LBW infant. Infertile women do not appear to be at increased odds for PTD.