Sono-embryonic detection of monochorionic, diamniotic triplets with conjoined twins after in vitro fertilization: A case report and review of the literature

Monochorionic diamniotic triplets with a conjoined pair are exceedingly rare and arise from multiple splitting events of a single zygote. This report presents the earliest documented ultrasound diagnosis of MCDA triplets with a conjoined pair, at 8 weeks and 5 days of gestation, in a patient who underwent in-vitro fertilization with a single embryo transfer. High-resolution transvaginal ultrasound revealed a monochorionic diamniotic configuration with two amniotic sacs: one containing a structurally normal embryo and the other containing di-thoracic parapagus conjoined twins. This case highlights the critical role of ultrasound imaging in the embryonic period to accurately identify complex multifetal pregnancies and to facilitate timely counseling and clinical decision-making. A review of the literature is included to provide context and management considerations for this rare condition.