Prenatal diagnosis of sirenomelia in the first trimester

Abstract

Sirenomelia is a rare and fatal congenital anomaly. Early prenatal diagnosis by first trimester scan should be the aim to minimize the physical and psychiatric trauma related to the termination of pregnancy at advanced gestation. Nulliparous woman aged 23 years was referred for evaluation because of absence of legs at 12 weeks 6 days of gestation. The upper half of the fetus appeared normal. The lower extremities appeared to be fused together in fixed extension and mobility at the hip and knee joints was restricted. A single umbilical artery was demonstrated using color doppler, Also, omphalocele was detected and the final diagnosis was sirenomelia. Parents opted for the pregnancy termination due to the lethal prognosis for the fetus. Etiological factors of sirenomelia sequence are still unclear. Several heterogeneous risk factors have been reported, but all of them are debatable. Anomalies of kidneys, significant oligohydramnios and concomitant hypoplasia of the lungs make a very unfavorable prognosis for sirenomelia. Ultrasonographic diagnosis of the sirenomelia in second trimester may be prevented by severe oligohydramnios, which is caused by renal agenesis or dysgenesis. Termination of the pregnancy is an option due to a lethal prognosis. It should be offered to the parents when diagnosis of the sirenomelia is made. First trimester diagnosis will give oppurtunity to the patient more safer and less traumatic termination procedure