Nulliparity, fertility treatments and twins: a time for rethinking.

Objective: To evaluate the risk that nulliparity poses to the outcome of twin pregnancies, an issue that gained importance due to the rise of twin gestations following assisted reproduction interventions.

Design: A prospective cohort study.

Setting And Patient(s): Between January 1, 2004, and January 7, 2008, we prospectively enrolled all pregnancies achieved by assisted reproduction techniques and including ovulation induction, which successfully completed the first trimester. Pregnancies achieved by egg donation were excluded.

Main Outcome Measure(s): Second trimester abortion and severe prematurity (delivery before 32 weeks) rates and the number of live births.

Result(s): Two-hundred-forty-three twin pregnancies were available for evaluation. Second trimester miscarriage rate was 9.3% in nulliparas and 2.4% in multiparas (P=0.061). Severe prematurity rate was 15.1% in nulliparas compared with 2.5% in multiparas (P=0.003). Better outcome of multiparas was also demonstrated by the calculated chance of taking home at least one baby: 97.6% for multiparas compared with 89.2% in nulliparas (P=0.024).

Conclusion(s): Nulliparity is a risk factor for a poor outcome in twin pregnancies achieved by fertility treatments and is associated with an increased risk for severe prematurity and possibly late abortions. This information should be relayed to the patients undergoing fertility treatments and is a consideration regarding the number of fetuses in relation to parity.