Private Clinic of Obstetrics and Gynecology, Varna, Bulgaria.
Introduction
Conjoined twins, rare variants of monozygotic twins, result from an incomplete division of the embryonic disk after the 13th day of conception. Conjoined twinning occurs once in every 50,000-100,000 births. Cephalothoracopagus, a very rare variant of conjoined twins occurs once in every three-million births. Early prenatal diagnosis is desirable, given the poor prognosis.
The earliest diagnosis of cephalothoracopagus twins reported in the literature was made by vaginal ultrasound at the 8 weeks of gestation. A false positive result in the first trimester may result from the too close proximity on the fetuses. Therefore, a definitive diagnosis with conventional ultrasound is generally made only in the early third trimester, when a detailed assessment of the degree of fusion can be made.
3D ultrasound imaging at the 10 weeks of gestation can generate accurate, surface-rendered images of the twins, assessing the anatomical relationship of the craniofacial structures, fetal skeleton, spine and thorax. 3D power Doppler can be used for vascular anatomy mapping at the conjoined site.
Management of the the conjoined twins depends on the location and range of fusion and the potential prognosis after delivery. In case of the pregnancy termination before 3rd trimester, we prefer a vaginal route of termination. Vaginal route of delivery is suitable for small nonviable fetuses. The technique of the delivery is very important. Cesarean section is preferred later on due to a potential high risk of the dystocia. It is reserved for the larger fetuses or the cases where the viability is desired.
Case report
A 29-year old G5 P2 came to our department for the polyhydramnios assessment, which was diagnosed by her physician. It was an uncomplicated pregnancy so-far. Patient had no contributive personal or family history. No history of consanguinity, twin pregnancy, diabetes or ovarian stimulation. During the ultrasound examination we saw the fetus with one head of the normal biometry. Thorax was of an unusual large size. There were two separate hearts of the different sizes and multiple extremities.
The fetus corresponded to 31-weeks of gestation according to the fetal biometry. A monochorionic, monoamniotic gestation with conjoined male twins was diagnosed. There was a single head with a normal face, difficult for morphological evaluation, due to a specific position of the fetus. Two unfused spines, a fused thorax with two hearts, and eight extremities. There were two penises with hypospadia.
After the counselling, the couple opted for the pregnancy termination.The pregnancy termination was performed via cesarean section. The fetal weight was 2900 grams and it measured 40 cm. An autopsy confirmed our diagnosis of the conjoined twins, cephalothoracopagus monosymmetros. Cephalothoracopagus monosymmetros = fused head, only one of the faces is developed; cephalothoracopagus disymmetros = fused head but equally developed faces directed laterally.
Images 1,2: Image 1. Image 2 shows 3D of the fetal thorax and extremities.