Xipho-omphalopagus conjoined twins in a spontaneous triplet pregnancy: autopsy findings.

Abstract

Conjoined twins (CTs) occur in 1 per 50,000 to 100,000 live births with a female predominance (F:M, 3:1).[1-3] It is exceptionally rare in triplet preg-nancies. The aim of this report is to describe autopsy findings of conjoined twins in a spontaneous triplet pregnancy diagnosed by ultrasound prenatally. A 20-year-old woman, gravid-1 para-0, was referred to the Gynaecology and Obstetrics Department at 21-weeks gestation with a diagnosis of CT in a spon-taneous triplet pregnancy. There was no history of twinning in the family and medication use during ear-ly pregnancy. At referral, transvaginal ultrasound revealed a monochorionic-diamniotic triplet pregnan-cy with a set of CTs. One amniotic sac contained a single female foetus; the second amniotic sac had a set of CT fused through the thorax and abdomen. They had two heads, separate hearts and stomachs, two pelvises, four arms and four legs. An extensive counselling of the parents was done regarding the management options. The parents opted termination of pregnancy. Autopsy revealed a normal female foetus and a set of CTs (Fig. 1).The conjoined foe-tuses were xipho-omphalopagus, joined in midline, from the lower part of the sternum to the umbilicus. They shared a single umbilical cord with two umbili-cal arteries and two umbilical veins. They had sepa-rate chests, separate hearts and lungs with a contin-uous diaphragm. They shared a common centrally placed fused liver. The intestines were also fused from the mid portion of duodenums to distal ileum. Normal kidneys, urinary bladders, and female genital tracts were noted in each of the twins. Embryology of CTs is explained by fission theory which proposes incomplete separation of the inner cell mass of a monozygotic twins; and fusion theory based on the secondary union of two originally sepa-rate monozygotic embryonic discs.[1,4] According to another hypothesis CTs result from the development of two co-dominant notochords during gastrula-tion.[4] Moreover, factors that induce calcium de-pression and delayed implantation encourage uniovular duplication in general and conjoined twin-ning in particular.[5] This hypothesis could explain the occurrence of CTs in our case as the mother was from a low socio-economical background with de-creased calcium intake in diet. This may be a reason for triplet pregnancy as well as conjoined twinning. Other possible teratogenic factors are oral contra-ceptives, clomiphene, and oral griseofulvin.[6]