Conjoined Twins in a Triplet Pregnancy

Abstract

Conjoined twins have an incidence of about 1 in every 50,000 to 100,000 births., Ultrasound can play a major role in identifying and assessing conjoined twins as well as determining the degree of fusion between the fetuses. Another complication arises when a normal third fetus is present with the conjoined twins. We present a rare case of conjoined twins in a triplet pregnancy diagnosed prenatally with ultrasound. SONOGRAPHIC FINDINGSA 19-year-old white woman (gravida 2, para 1, abortion) was referred to our medical center from another facility. Sonographic evaluation was requested for fetal age and suspected abnormalities in a multiple gestation with the possibility of conjoined twins in the upper sac.Real-time ultrasound demonstrated a well-defined septum coursing between the two gestational sacs. The placenta was located posteriorly in the lower sac and anteriorly in the upper sac. Both placentas appeared normal in size and thickness.The lower sac contained a normal-appearing fetus in a transverse lie. Ultrasound measurements were consistent with approximately 17 menstrual weeks, and normal amniotic fluid volume was present.Conjoined twins were noted in the upper gestational sac in a transverse lie with a fused and irregularly shaped head. The head was increased in transverse diameter and two small orbits were noted as well as at least one ear in an abnormal position. There was a midline falx or septum with two widely separated areas of choroid plexus. Only one posterior fossa was evident. Two spines terminated at the common head (Fig. 1). Fusion was noted at the level of the abdomen and chest with separate pelves. There appeared to be a common liver. A single four-chamber heart with a normal rate and rhythm was noted in the right side of one fetus. The stomachs were not definitely seen; however, both urinary bladders were identified (Fig. 2). There were four lower extremities, including four feet, and four upper extremities, probably including four hands. No spinal defects were evident. The amniotic fluid volume was slightly increased in the upper sac.All three fetuses were male.The pregnancy was terminated, and gross pathologic and radiologic examinations were performed. The report from pathology described the following: 1. A normal-appearing male fetus that weighed 201 g and measured 21.5 cm in length 2. Male cephalothorocopagus twins that weighed 248 and measured 17.5 cm in length (Fig. 3)