Triploidy: 109 Prenatal Diagnoses

Abstract

Triploidy is a common finding both in early spontaneous miscarriages and in the fetal period, presenting in 1–2% of pregnancies. It may be the result of diandry (an extra paternal haploid set) or digyny (an extra maternal haploid set).

Diandry predominates in cases of triploidy without embryos after nine weeks or in the second trimester with fetuses of relatively normal size and with placental findings of partial hydatidiform mole. Digyny predominates in early miscarriages before nine weeks with embryos or in the second trimester with fetuses with a marked asymmetrical intrauterine growth retardation and a small placenta. We reviewed 109 prenatal diagnoses of triploidy in a ten-year period. In the group with the first trimester diagnosis <14 weeks (n=62), an interesting finding is the high percentage of recurrent miscarriage as an indication for chromosomal analysis (n=26/62; 42%). In the second and third trimesters <14 weeks (n=47), 29 cases had ultrasound characteristics of digynic triploidy with an asymmetrical fetal growth retardation with oligohydramnios of which three pregnancies continued above 20 weeks with abnormal Doppler waveforms and velocities. Thirteen cases had ultrasound characteristics of diandric triploidy with only mild growth retarded or normal grown fetuses with a thickened placenta. Other indications for chromosomal analysis were maternal age (n=1) and a positive maternal serum triple test screening without ultrasound specifications (n=4).

Early prenatal recognition of triploid pregnancies, certainly those with placental findings of partial hydatidiform mole, is important since these mothers are at risk of preeclampsia and persistent trophoblastic disease.