To investigate whether the outcome of a pregnancy is related to the time required to achieve that pregnancy (TTP).The distribution of the TTP for pregnancies ending in multiple birth, early (before week 12) and late (weeks 12-28) miscarriage, stillbirth, and extrauterine pregnancy was compared to that of pregnancies ending in singleton birth. Furthermore, the distribution of the TTP for preterm singleton births was compared to that of full-term singleton births.Sweden.Information from three previous studies on reproduction was used: Women chosen for exposure to persistent organochlorine pollutants, or exposure as a hairdresser, and their respective controls.None.Self-reported pregnancy outcome.An increased TTP (i.e., decreased fecundability) was associated with pregnancies ending in miscarriage (early as well as late) and extrauterine pregnancies. Pregnancies ending in multiple live birth tended to have shorter TTPs than those ending in single live birth. No association between TTP and stillbirths was found. Among women whose pregnancies ended in singleton birth, a prolonged TTP was associated with preterm delivery.The TTP of a pregnancy seemed to be associated with the outcome of that pregnancy. The mechanisms behind this phenomenon are, however, unclear.