Triploidy in a twin pregnancy: small placenta volume as an early sonographical marker.

INTRODUCTION

We report a case of a twin pregnancy with triploidy of maternal phenotype of one foetus and no chromosomal anomaly of the other twin and the role of sonographical placental volumetry.

CASE: At 12 weeks of gestation, a dichorionic twin pregnancy discordant in growth is diagnosed. 3D ultrasound reveals a distinctly small placental volume of foetus II. Amniocentesis at 16 weeks discloses triploidy of this foetus. Sonography reveals asymmetrical foetal growth retardation, a severe heart defect and bilateral cleft lip and palate, typical findings in triploidy. Selective feticide at week 20+3 is followed by pre-term birth of foetus I at 27 weeks.

CONCLUSION

Small placental volume in addition to growth restriction of one foetus early in the course of a twin pregnancy could be an important early marker influencing the decision for chorionic villous sampling at 12 weeks instead of amniocentesis at 16 weeks and it could lead to an earlier selective pregnancy termination of a triploid twin. This would lower the risk of pre-term birth and enable a better outcome for the remaining healthy foetus.