Protocol for the prospective observational clinical study: estimation of fetal weight by MRI to PREdict neonatal MACROsomia (PREMACRO study) and small-for-gestational age neonates

Abstract

IntroductionMacrosomia refers to growth beyond a specific threshold, regardless of gestational age. These fetuses are also frequently referred to as large for gestational age (LGA). Various cut-offs have been used but for research purposes, a cut-off above the 95th centile for birth weight is often preferred because it defines 90% of the population as normal weight. The use of centiles, rather than estimated weights, also accommodates preterm macrosomic infants, although most of the complications, maternal and fetal, arise during the delivery of large babies at term. This means that accurate identification of LGA fetuses (≥95th centile) may play an important role in guiding obstetric interventions, such as induction of labour or caesarean section. Traditionally, identification of fetuses suspected of macrosomia has been based on biometric measurements using two-dimensional (2D) ultrasound (US), yet this method is rather sub-optimal. We present a protocol (V.2.1, date 19 May 2016) for the estimation of fetal weight (EFW) by MRI to PREdict neonatal MACROsomia (PREMACRO study), which is a prospective observational clinical study designed to determine whether MRI at 36 + 0 to 36 + 6 weeks of gestation, as compared with 2D US, can improve the identification of LGA neonates ≥95th centile.Methods and analysisAll eligible women attending the 36-week clinic will be invited to participate in the screening study for LGA fetuses ≥95th centile and will undergo US-EFW and MRI-EFW within minutes of each other. From these estimations, a centile will be derived which will be compared with the centile of birth weight used as the gold standard. Besides birth weight, other pregnancy and neonatal outcomes will be collected and analysed. The first enrolment for the study was in May 2016. As of September 2018, 2004 women have been screened and recruited to the study. The study is due to end in April 2019.Ethics and disseminationThe study will be conducted in accordance with the International Conference on Harmonisation for good clinical practice and the appropriate regulatory requirement(s). A favourable ethical opinion was obtained from the Ethics Committee of the University Hospital Brugmann, reference number CE2016/44. Results will be published in peer-reviewed journals and disseminated at international conferences.Trial registration numberNCT02713568.

MRI-Derived Fetal Weight Estimation in the Midpregnancy Fetus: A Method Comparison Study

“…Kadji et al [41] found a random error of ±1.9% and 8.8% in MRI and US, respectively, for intraobserver measures (±1.6% and 3.4% in our study) and ±2.8% and 11.2% for interobserver measurements (±2.6% and 3.5% in our study). The larger US errors reported by Kadji et al [41] are likely to reflect increased proportional bias, observed when random errors increase as US measurements become larger at a later GA (in this case, term), a phenomenon described by obstetric US-observer variation studies [38]. In our sample (second trimester), this high proportional variation is not seen with US due to smaller fetal sizes.…”

“…Other studies report that a significant proportion of US random errors (between 58 and 80%) is incurred through observer variations in caliper placement, and for these cases, training and quality audit will help to some degree but not entirely [14,[38][39][40]. Kadji et al [41] found a random error of ±1.9% and 8.8% in MRI and US, respectively, for intraobserver measures (±1.6% and 3.4% in our study) and ±2.8% and 11.2% for interobserver measurements (±2.6% and 3.5% in our study). The larger US errors reported by Kadji et al [41] are likely to reflect increased proportional bias, observed when random errors increase as US measurements become larger at a later GA (in this case, term), a phenomenon described by obstetric US-observer variation studies [38].…”

Fetal magnetic resonance imaging at 36 weeks predicts neonatal macrosomia: the PREMACRO study

“…The inclusion criteria for the study were age of 18 years or older, singleton pregnancy, live fetus at 36 0/7 to 36 6/7 weeks' gestation, planning for a delivery in our maternity ward at the University Hospital Brugmann, Brussels, Belgium. The exclusion criteria were as follows: unconscious or severely ill women, those with learning difficulties or mental handicap, multiple pregnancy, major fetal abnormality identified at routine first-, second-, or third-trimester scans, no first-trimester scan (risk of imprecise dating), presentation outside the target gestational age window, known contraindication to MRI, 23 painful regular uterine contractions or history of ruptured membranes, patients already recruited in a previous pregnancy, women delivering before MRI and US evaluation, neonatal weight measured >6 hours after the birth for any reason, patients with history of stillborns.…”

“…Details of the MRI-EFW method have been described previously. 23 Briefly, MRI was performed using a clinical 1.5 T wholebody unit with a gradient field strength AJOG at a Glance Why was this study conducted? This study aimed to determine whether prenatal magnetic resonance imaging performs better than ultrasound in the prediction of large-for-gestational-age (LGA) and small-for-gestational-age neonates.…”

The use of magnetic resonance imaging in the prediction of birthweight

“…Following many years of research aimed at optimizing and simplifying the technique, as described earlier in this review, we finally began recruiting to the PREMACRO study in May 2016. This is a large prospective observational study comparing gold standard US‐EFW with MRI‐EFW in order to decide if one technique is superior to the other and to what extent . Recruitment has recently concluded with a total of over 2340 patients with singleton pregnancies, including over 90 macrosomic neonates defined as greater than or equal to 95th centile for gestational age.…”