Dichorionic triamniotic triplet pregnancy with monozygotic twins discordant for trisomy 13 after preimplantation genetic screening: case report

Objective

To report the first dichorionic triamniotic triplet pregnancy discordant for trisomy 13 after in vitro fertilization (IVF) treatment with preimplantation genetic screening (PGS).

Design

Case report.

Setting

Private IVF center.

Patient(s)

A 40-year-old para 1+6 woman.

Intervention(s)

IVF combined with PGS for chromosomes 13, 16, 18, 21, and 22, resulting in the transfer of two embryos.

Main Outcome Measure(s)

Prenatal fetal ultrasonography revealed a dichorionic triamniotic triplet pregnancy. An amniocentesis, performed at 15-weeks' gestation, confirmed that the singleton and one monozygotic twin were normal but the other monozygotic twin was trisomy 13.

Result(s)

After diagnosis and counseling, selective termination of the trisomy 13 monozygotic twin was performed at 16 weeks and 4 days. At 18 weeks and 4 days the co-twin died. A healthy boy was delivered by elective caesarean section at 36–weeks' gestation.

Conclusion(s)

Assisted reproductive techniques that breach the embryo's zona pellucida such as assisted hatching and PGS embryo biopsy increase the incidence of monozygotic twins. Due to high levels of mosaicism in human preimplantation embryos, PGS cannot ensure that embryos diagnosed as normal and selected for transfer do not contain abnormal cells. Hence, further reports of discordant monozygotic twins following PGS are expected, emphasizing the need for appropriate counseling of patients wishing to embark on an IVF/PGS treatment cycle.

Key Words: Discordant, monozygotic, twins, trisomy 13, PGS