Sirenomelia in twin pregnancy: A case report and literature review.

RATIONALE: Sirenomelia is a very rare congenital malformation and characterized by fused lower extremities, oligohydramnios, renal agenesis, absent urinary tract and external genitalia, single umbilical artery, and imperforate anus. Ultrasonography is an optimal method for prenatal screening and diagnosis of sirenomelia. The incidence of sirenomelia in the twin pregnancy is extremely low.

PATIENT CONCERNS: We reported a case of 1 twin with sirenomelia in dichorionic-diamniotic twin pregnancy after in vitro fertilization and embryo transfer.

DIAGNOSES: The sirenomelia twin was diagnosed at the 2nd trimester by ultrasonic examination and complicated with oligohydramnios and a single umbilical artery, another twin was normal.

INTERVENTIONS: A regular and careful antenatal care was conducted. The parents refused to examine the chromosome of sirenomelia twin, and the chromosomal microarray analysis of the amniotic fluid sample was only achieved in the normal anatomy twin after extensively counseled by the multi-disciplinary team.

OUTCOMES: At 34+2 gestational weeks, the demise of the malformed twin occurred, while fetal heart rate monitoring of the normal twin was abnormal, and an emergency cesarean section was performed. A healthy male baby was delivered with Apgar scores of 10 and 10 at 1 and 5 minutes, respectively. The mother and the baby were followed up and are in good health until now.

CONCLUSION: Sirenomelia is a lethal condition in the perinatal period. Early antenatal diagnosis is very important. Voluntary selective termination of sirenomelia 1 in twin pregnancy may be advised. Expecting parents should be counseled by the multidisciplinary team about the management and prognosis of the sirenomelia.