Estimation of Fetal Weight by MR Imaging to PREdict Neonatal MACROsomia (PREMACRO Study)

Macrosomia and growth restriction are important causes of perinatal morbidity, at or near to term. However, clear identification of 'at risk' foetuses is difficult and clinical estimates of fetal weight are poor. Historically, ultrasound has been used as a second line in such cases but the accuracy of this imaging modality in the mid- to late third trimester is also limited. Estimated fetal weight (EFW) is an important part of the clinical assessment and is used to guide obstetric interventions, when a fetus is small or large for dates. It frequently is the single most important component guiding interventions, such as induction of labour or Caesarean section. Due to the imprecision of ultrasound-derived EFW, particularly in cases of suspected macrosomia in the 3rd trimester, the investigators believe that these estimates should not be used to make important obstetric decisions regarding mode and timing of delivery and that a more accurate method of assessment could produce better outcomes by restricting interventions to those foetuses at greatest risk. Some publications have already demonstrated that magnetic resonance (MR) imaging derived-EFW close to delivery, is more accurate than ultrasound The goal of the present study is thus to compare the performance of magentic resonance imaging derived-EFW, versus ultrasound derived-EFW at 36 weeks of gestation, regarding the prediction of neonatal macrosomia.