Prospective study of time to pregnancy and adverse birth outcomes

In this registry-based cohort study, we found positive associations between prospectively measured time to pregnancy and several adverse birth outcomes, including preterm birth, low birth weight, placental disorders, gestational diabetes, and cesarean section.

Lauren A. Wise, Sc.D., Ellen M. Mikkelsen, Ph.D., Henrik Toft Sørensen, M.D., Dr.P.H., Kenneth J. Rothman, Dr.P.H., Kristen A. Hahn, M.P.H., Anders H. Riis, M.S., Elizabeth E. Hatch, Ph.D.

Volume 103, Issue 4, Pages 1065-1073


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

Prospective cohort study.

Not applicable.

A total of 3,521 singletons born to women aged 18-40 years at cohort entry.


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

Multivariable RRs for PTB in relation to TTP of 3–5, 6–11, and ≥12 vs.

In a prospective cohort study of Danish pregnancy planners, delayed conception was a marker for adverse birth outcomes, after accounting for fertility treatment.

  • Shvetha Zarek

    This is a fascinating study from the preeminent epidemiology group at Boston University. Can the authors kindly comment on why couples who underwent fertility treatment were included in this study? It would have been interesting to see if a longer TTP is associated with adverse birth outcomes in a cohort of spontaneous conceptions only. Although adjusting for fertility treatment is valid, it is answering a different research question. Thank you.

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