Thoraco-omphalopagus Conjoint Twin: A Case Report and Literature Review

Conjoined twins are a rare phenomenon of a monochorionic monoamniotic twin. The incidence varies from 1 in 50000 to 1 in 100000 live births [1,2]. Female foetuses are more commonly affected with the ratio of male to female being 1:3, particularly in thoracopagus type [3]. Five types of conjoint twins are classically described, Thoracopagus, Omphalopagus, Pygopagus, Ischiopagus and Craniopagus. With a reported incidence of 7475% of all conjoint twins, Thoracopagus is the most common type. Omphalopagus with an incidence of 0.5% is the least common. Spencer et al divided the conjoined twins into following three major groups: twins with a ventral union, twins with a dorsal union and twins with a lateral union [2]. The first major group according to site of fusion includes: cephalopagus (head), thoracopagus (chest), Omphalopagus (umbilicus) and ischiopagus (hip). The dorsal union includes three types namely: pygopagus (sacrum), rachipagus (spine) and craniopagus (cranium). The last major group includes only one type of twins that is parapagus (side) twins [2]. Incidence of thoraco-omphalopagus is 28% [3]. If the diagnosis could be made before fetal viability, termination of pregnancy is offered to the patient. Conjoint twins can be diagnosed by pre natal ultrasound. However in underdeveloped countries which lack adequate maternal health care facilities, diagnosis could be delayed. Preterm delivery is most common outcome. Vaginal delivery is reserved for still births and conjoined twins who do not survive [4]. Around 40% of the conjoint twins are stillborns and around 35% die within 24 hours of delivery [4]. In thoracopagus, the perinatal outcome is determined by the degree of fusion of the heart [5]. In the order of the frequency, the pygopagus twins have better prognosis than the Omphalopagus and the thoracopagus twins.