Associations between unfavorable outcomes in successive pregnancies

Spontaneous abortions in preceding pregnancies were associated with a significantly increased risk of preterm births (less than 37 weeks) and intrauterine growth retardation in the index pregnancies that followed next, even when the effects of risk factors for the index pregnancy were controlled. The predictive effect of the earlier spontaneous abortion was independent of the effect of the risk factors, even though the latter's effect was over twice as great as indicated by odds ratios. The most serious types of severe intrauterine growth retardation occurred more frequently in high-risk than in low-risk pregnancies. Among mothers whose previous pregnancy resulted in low birth weight, the current pregnancy almost always had one or more risk factors.