Mode of conception does not affect fetal or placental growth parameters or ratios in early gestation or at delivery

Ratio of fetal weight to placenta size varies by mode of conception (fertility treatments utilized) in animals. Our objective was to assess whether fertility treatments also affect these ratios in humans.

In this retrospective study, we assessed two cohorts: (a) early gestation cohort, women with singleton pregnancies who underwent first trimester vaginal ultrasound and (b) delivered cohort, women who delivered a live-born, singleton infant with placenta disposition to pathology. Crown rump length (CRL) and estimated placental volume (EPV) were calculated from first trimester ultrasound images using a validated computation. Infant birth weight (BW), pregnancy data, placental weight (PW), and placental histopathology were collected. Fetal growth-to-placental weight ratios (CRL/EPV; BW/PW) and placentas were compared by mode of conception. Linear regression was used to adjust for confounding variables.

Two thousand one hundred seventy patients were included in the early gestation cohort and 1443 in the delivered cohort. Of the early gestation cohort (a), 85.4% were spontaneous conceptions, 5.9% Non-IVF Fertility (NIFT), and 8.7% IVF. In the delivered cohort (b), 92.4% were spontaneous, 2.1% NIFT, and 80 5.5% IVF. There were no significant differences between fetal growth-to-placental weight parameters, ratios, and neonatal birth measurements based on mode of conception. Placenta accreta was significantly higher in the patients receiving fertility treatments (1.2 versus 3.6%, p < 0.05).

Mode of conception does not appear to influence fetal growth-to-placental weight ratios throughout gestation. In addition, findings in animal models may not always translate into human studies of infertility treatment outcomes.