Evaluation of the impact of vasa previa on feto-placental hormonal synthesis and fetal growth.

Introduction: A vasa previa (VP) refers to aberrant chorionic vessels which can either connect the chorionic plate to a velamentous cord (type I) or a succenturiate or accessory lobe to the main placental mass (type II).

Methods: We performed retrospective cohort study of 32 singleton pregnancies diagnosed with VP. The levels of maternal serum alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG) and unconjugated estriol (uE3) were measured at 15-18 weeks as part of the triple test screening for Trisomy 21. The data were subdivided according to the type of VP and compared with those of a control group with central cord insertion and no succenturiate or accessory placental lobe.

Results: Twenty one (65.6%) parturient women presented with VP type I and 11 (34.4%) with VP type II. The mean birthweight and placental weight was significantly higher in pregnancies with VP type II than in pregnancies with VP with VP type I (3037.3±400.9 gr vs 2493.5±491.6 gr; p=0.004 and 511.0±47.2 gr vs 367.1±64.3 gr; p<0.0001; respectively). The mean hCG level in VP type II was significantly (p<0.001) higher than those with type I (2.38MoM vs 1.17MoM) and compared to controls (2.38MoM vs 0.99MoM).

Conclusions: There is no obvious impact on both placental and fetal growth in VP type II. By contrast, VP type I is associated with slower feto-placental growth secondary to impaired development and biological functions of the placenta during the first half of pregnancy.