Intrauterine growth restriction (IUGR) is defined as the pathologic inhibition of intrauterine fetal growth and the failure of the fetus to achieve its growth potential. Identification, proper management and possible prevention of IUGR are important objectives of fetal medicine. The etiology of the disease is likely multifactorial, involving both fetal adaptation responses and impaired placentation leading to decrease transfer of oxygen and nutrients from the mother to the fetus secondary to defective extravillous trophoblast invasion. This pathophysiological mechanism may be responsible for the early onset IUGR. Nevertheless, IUGR is a process that starts before a pathologically small fetal size can be identified. Currently, no combination of markers performs well as a screening test for IUGR at first trimester of pregnancy. Umbilical vein blood flow, closely related to the mass of placental cotyledons and placental volume as well as placental vascular indices have been investigated in the first trimester but studies are scarce and contradictory.
Given the importance of being able to prevent and treat promptly IUGR fetuses, the main objective of the present prospective observational study is therefore to analyze placental volume and placenta vascular index using of 3-dimensional power Doppler at gestational ages of 11 weeks to 13 weeks 6 days, to relate these results to umbilical vein blood flow and secondarily to investigate whether these parameters are useful to predict the subsequent appearance of intrauterine growth restriction.
The underlying mechanism of IUGR involves impaired placentation leading to decreased transfer of oxygen and nutrients from the mother to the fetus (Hui 2008). Early identification of fetuses developing IUGR is therefore of great clinical interest, since their antenatal detection has been shown to reduce significantly perinatal morbidity and mortality (Lindqvist 2005).
Rizzo et al described related umbilical vein blood flow (UVBF) and umbilical vein (UV) time-averaged maximum velocity (TAMXV) to the subsequent development of IUGR in pregnancies characterized by low maternal serum pregnancy-associated plasma protein A (PAPP-A) concentrations (Rizzo 2010). Actually, data do not support the use of PAPP-A values alone as a diagnostic tool in the identification of the subgroup of pregnancies that will go on to develop IUGR and result in adverse pregnancy outcome. No study was conduced with analyses of UVBF and UV-TAMXV as screening in all pregnancies undergoing first trimester ultrasound scan, regardless of PAPP-A value.
Furthermore, in the second and third trimester, several authors have shown a correlation between 3-dimensional power Doppler (3-DPD) indices and a concomitant diagnosis of IUGR (Pomorski 2012). However, studies assessing first trimester placental volume and vascularization in pregnancies with IUGR are scarce and contradictory. For this reason, we decide to conduce this study. This will be the first study in the literature to report the correlation between placental volume and placenta vascularization index (VI), flow index (FI), vascularization-flow index (VFI) using 3-DPD and umbilical vein blood flow (UVBF, UV-TAMXV, UV diameter) as predictors of early onset IUGR in pregnancies undergoing ultrasound routine scan at at 11 weeks to 13 weeks 6 days. We believe that the main strengths of the present study are its design, with prospective recruitment and follow-up, the use of customized birth weight curves, the construction of different models to predict IUGR at first trimester combining multiple variables to identify the most efficient, and lastly, to describe the correlation between early onset pre-eclampsia (PET) and early onset IUGR.