VP31.03: Recurrent triploidy: a rare case report with a recognisable phenotypic pattern

Abstract

Triploidy associated with fetal development and survival beyond the first trimester of pregnancy is rare and a wide range of phenotypic presentations is described. There are still no susceptibility factors identified; current knowledge supports the theory that there is no increased risk for recurrence of triploidy after a first triploid pregnancy. We report a case of two consecutive triploid pregnancies achieving the 2nd trimester of pregnancy in a Caucasian woman. She had three singleton spontaneous pregnancies: the first one was a non-complicated pregnancy at 29 years old, resulting in a healthy newborn delivered at term, the second was a triploid pregnancy at 32 years old and the third a triploid pregnancy at 34 years old. In both triploid pregnancies similar findings were identified, such as: 1st trimester screening revealing low levels of PAPP-A and free β-HCG; 1st trimester ultrasound with no major anatomic defects and a normal NT measurement; 2nd trimester ultrasound revealing a restricted fetus with an increased cephalic circumference/abdominal circumference ratio, oligohydramnios and the presence of cerebellar vermis hypoplasia. Both pregnancies were electively terminated during 2nd trimester, after an amniocentesis showing a triploid karyotype. In both cases, fetal autopsy revealed a small fetus with macrocephaly, cerebellar vermis hypoplasia, low implantation of the ears, hypertelorism, proptosis, small nose, micrognathia, syndactyly between the 2nd and 3rd fingers and club foot; placenta had low weight for gestational age and umbilical cord had a single umbilical artery. Reported findings are highly suggestive of digynic recurrent triploidy. Considering the significant phenotypic variation in triploidy, the finding of a specific phenotypic pattern in both recurrent triploid pregnancies raises the question if there is a genetic basis for this condition: further studies are needed to evaluate this hypothesis, which could revolutionise prenatal counselling.