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.