Assisted conception and placental perfusion assessed by uterine artery Doppler at 11-13 weeks' gestation.

BACKGROUND: Pregnancies conceived by IVF are at increased risk of pre-eclampsia (PE). This study examines the potential mechanism for such association by examining the effect of method of conception on placentation as assessed by uterine artery Doppler at 11-13 weeks' gestation.

METHODS: This prospective screening study at 11(+0)-13(+6) weeks for PE in singleton pregnancies used a combination of maternal history and uterine artery pulsatility index (PI). Regression analysis was performed to examine the association between the method of conception and both uterine artery PI and development of PE, after adjustment for maternal characteristics and obstetric history.

RESULTS: In the study population of 27 461 pregnancies, conception was spontaneous in 26 538 (96.6%), by IVF in 426 (1.6%) and by use of ovulation induction (OI) drugs in 497 (1.8%) pregnancies. Conception by IVF was associated with an increase in risk for early-PE, requiring delivery before 34 weeks [odds ratio 3.94, 95% confidence interval (CI) 1.51-10.27] but not for late-PE. In the OI group, the risk of early- and late-PE was not increased. In addition to IVF, other significant contributors to the prediction of early-PE were maternal weight, height, African and South Asian racial origin, previous and family history of PE and history of chronic hypertension. Significant contributions in explaining log(10) uterine artery PI were provided from maternal characteristics but not from the method of conception. The median uterine artery PI multiple of the median (MoM) in the IVF group (1.02 MoM) and in the OI group (1.03 MoM) were not significantly different from that of the spontaneous conception group (1.01 MoM; P= 0.870 and P= 0.296, respectively).

CONCLUSIONS: Conception by IVF substantially increases the risk for early-PE, through a mechanism unrelated to clinically measurable impairment in placental perfusion.