• Article

Prospective study of time to pregnancy and adverse birth outcomes

Objective: To investigate the association between time to pregnancy (TTP) and adverse birth outcomes.

Design: Prospective cohort study.

Setting: Not applicable.

Patient(s): A total of 3,521 singletons born to women aged 18-40 years at cohort entry.

Intervention(s): None.

Main Outcome Measure(s): Selected birth outcomes, including preterm birth (PTB,

Result(s): Multivariable RRs for PTB in relation to TTP of 3-5, 6-11, and >= 12 vs. = 12 vs. = 12 cycles) were associated with increased risks of low birth weight (RR 1.80, 95% CI 0.97-3.35), cesarean delivery (RR 1.64, 95% CI 1.27-2.12), placental disorders (RR 2.21, 95% CI 1.07-4.56), ischemic placental disease (RR 1.56, 95% CI 0.99-2.44), pre-eclampsia (RR 1.45, 95% CI 0.79-2.65), and postpartum hemorrhage (RR 1.58, CI 1.14-2.19), and decreased risks of macrosomia (>= 4,500 g; RR 0.63, 95% CI 0.35-1.13) and large for gestational age (RR 0.76, 95% CI 0.58-1.00). Longer TTP showed little association with small for gestational age.

Conclusion(s): In a prospective cohort study of Danish pregnancy planners, delayed conception was a marker for adverse birth outcomes, after accounting for fertility treatment. (C) 2015 by American Society for Reproductive Medicine.


Wise, L. A., Mikkelsen, E. M., Sorensen, H. T., Rothman, K. J., Hahn, K. A., Riis, A. H., & Hatch, E. E. (2015). Prospective study of time to pregnancy and adverse birth outcomes. Fertility and Sterility, 103(4), 1065-1073.e2. https://doi.org/10.1016/j.fertnstert.2015.01.024