Differential diagnosis, investigations and treatment
The first ultrasound of her second pregnancy performed at 9 weeks and 6 days showed an embryo measuring 36 mm with cardiac activity and two ventricular flows in power Doppler but the placenta exhibited cystic, grape-like features (Figure 1). On the same day, human chorionic gonadotropin (hCG) serum levels were obtained at 221 944 UI/L, significantly above the median value of 74 655 UI/L (97th percentile) expected for this GA (4). A meeting with the genetics department and Maternal Fetal Medicine unit (MFM) was held to discuss the findings. The first trimester ultrasound, at 11 weeks and 6 days, showed an anterior, thickened, and heterogeneous placenta with molar-like features, an embryo with a normal nuchal translucency and no anatomical anomaly, a normal amniotic fluid quantity and a crown rump length correlated to the gestational age. Based on ultrasound findings, differential diagnosis of a partial mole with an euploid fetus or a complete mole with coexisting twin and PMD were considered. No signs of an evanescent twin were visible on ultrasonogram.
The maternal serum alpha-fetoprotein (MSAFP) at 12 weeks and 5 days was at 179.6 mcg/L, the median value at 12 weeks of GA being 18.75 mcg/L (5).
After multidisciplinary discussion, it was decided to carry out, with the couple’s information and consent, a transabdominal chorion villous sampling (CVS) at 13 weeks and 3 days. No triploidy was found and a PMD diagnosis was retained as most plausible after a thorough literature review. Consequently, a regimen of low-dose aspirin was initiated because of the high risk of early preeclampsia associated with PMD (3). Amniocentesis was carried out at 19 weeks and 4 days at parental demand due to the strong association with Beckwith Wiedemann Syndrome (BWS) (3). The results of microarray and molecular testing for BWS were normal as well as fetal anatomy scan at 20 weeks of GA. Subsequently the patient had a pathological oral glucose tolerance test at 26 weeks of GA and was diagnosed with gestational diabetes, which was kept under control with a diet throughout the pregnancy.
Fetal growth and well-being were followed closely every two weeks before 28 weeks of GA and on a weekly basis further. The growth was at about the 30th percentile (Intergrowth 21st curves) during the second trimester and the placenta maintained a thickened, hypo-echoic multicystic and heterogenous aspect. At 27 weeks of GA, an apical cystic zone evoking a thrombotic formation of 30x22x20 mm was detected on US. An additional investigation by MRI performed at 30 weeks showed a fundal placenta with dysplastic lesions measuring 5x9x3.9 cm consistent with the diagnosis of PMD (Figure 2). No fetal hepatic lesions were detected on MRI. From 32 weeks, the MFM team noted a slight decrease in fetal growth (11th percentile) and a few episodes of decreased subjective fetal movements were indicated by the mother with satisfactory ultrasound evaluation and monitoring. At 34 weeks and 5 days of GA, an additional thrombosis zone was observed in one of the dilated vessels of the chorionic plate with a central location, proximal to umbilical cord insertion.