Conjoined twins in dichorionic diamniotic triplet pregnancy: a report of three cases and literature review

BACKGROUND: Conjoined twins are a rare and serious complication of monochorionic twins. The total incidence is 1.5 per 100,000 births, and about 50% are liveborn. Prenatal screening and diagnosis of conjoined twins is usually performed by ultrasonography. Magnetic resonance imaging can be used to assist in the diagnosis if necessary. Conjoined twins in dichorionic diamniotic triplet pregnancy are extremely rare. CASE PRESENTATION: We reported three cases of dichorionic diamniotic triplet pregnancy with conjoined twins. Due to the poor prognosis of conjoined twins evaluated by multidisciplinary teams, selective termination of conjoined twins was performed in three cases. In case 1, selective reduction of the conjoined twins was performed at 16 gestational weeks, and a healthy female baby weighing 3270 g was delivered at 37 weeks. In case 2, the conjoined twins were selectively terminated at 17 weeks of gestation, and a healthy female baby weighing 2760 g was delivered at 37 weeks and 4 days. In case 3, the conjoined twins were selectively terminated at 15 weeks and 2 days, and a healthy female baby weighing 2450 g was delivered at 33 weeks and 6 days. The babies of all three cases were followed up and are in good health. CONCLUSION(S): Surgical separation is the only treatment for conjoined twins after birth. Early determination of chorionicity and antenatal diagnosis of conjoined twins in triplet gestations are critical for individualized management options and the prognosis of normal triplets. Expecting parents should be extensively counseled by multidisciplinary teams. If there are limitations in successful separation after birth, early selective termination of the conjoined twins by intrathoracic injection of potassium chloride may be a procedure in dichorionic diamniotic triplet pregnancy to improve perinatal outcomes of the normal triplet.