Case report
 
We present the case of a 29-year-old patient, G3P1, with unremarkable medical and family history. At the start of her pregnancy, the patient had an IUD (intrauterine contraception device); the IUD was located near the placenta and was left in place. She was first scanned in our clinic at 17 weeks GA.

The sonographer discovered a monochorionic twin pregnancy of 17 weeks GA (the fetuses sharing one placenta). The twin closer to the cervical os (Twin A) had normal morphology. The second twin (Twin B) was abnormal. The next ultrasound scan took place in the prenatal unit at Saint-Pierre Hospital at 25 weeks GA.
 
Several anomalous sonographic findings were made:
•      An omphalocele containing a portion of liver (Figure 1A, 1B);
•      Two spines; one of these was short (Figure 2A, 2B);
•      Two hearts inside the common thorax (Figure 3A, 3B);
•      An abnormal cranium:  neither the posterior fossa nor the falx cerebri was seen, (Figure 4A, 4B);
•      The face was abnormal (Figure 6);
•      A meningocele (Figure 5);
•      Abnormal upper extremities were discovered;
•      There was significant polyhydramnios (AFI > 25 cm). Amniotic drainage was accomplished, revealing a normal fetal karyotype of 46, XY.
The parents were informed of the situation. We suspected a triple pregnancy with conjoined twins. Selective interruption of pregnancy was not possible due to monochorionicity.  The excess of amniotic fluid was drained on two further occasions because of concern for uterine contractions from polyhydramnios .
 
Cesarean section was performed at 34 weeks GA. The first baby (Twin A) was normal (2080g, 
Apgar score of 10/10). The second baby (Twin B, 3000 g), died after 15 minutes of life.
 
The suspected diagnosis was confirmed at autopsy: triplet pregnancy, monochorionic/diamniotic, with single fetus (Twin A) and conjoined twin entity (thoracocephalophagus twins, referred to herein as "Twin Bâ€, one of them parabiotic).
 
Findings in "Twin B†:
 
• Two faces at the cephalic pole;
• On one side, there was a malformed face with hypotelorism and two ears;  
• On the other side, there was a primordial nose and two ears;
• The cranium was comprised of two frontal bones, four parietal bones, and two occipital bones;
• An occipital menigocele was seen on the parabiotic conjoined twin, which had a short spine;
• Two normal lower extremities, masculine genitalia, one bladder, and an omphalocele containing liver. There was only one normal digestive system with one pancreas;
• Amelia, two hearts, one thymus, one spleen, one liver, and two kidneys were seen.
 
• Cardiac findings for "Twin B†were abnormal, with ventriculoseptal defect and truncus arteriosus in one conjoined twin, and atrioventricular communication with pulmonary artery hypoplasia in the other.

Final diagnosis

Monochorionic, diamniotic triplet pregnancy with a single fetus and conjoined twins. The conjoined twins were thoracocephalopagus and heteropagus (asymmetrical), with two hearts in a shared thorax, a meningocele, and an omphalocele.

Figures 1A, 1B. Ultrasound examination at 25 weeks GA (transverse and longitudinal views) showing omphalocele with two stomachs (on transverse view).

Figures 2A, 2B. Ultrasound examination at 25 weeks GA (longitudinal view) showing two spines.

Figures 3A, 3B. Ultrasound examination at 25 weeks GA (transverse view) showing two hearts in the thorax.

Figures 4A, 4B. Ultrasound examination at 25 weeks GA (transverse view) showing abnormal organization of the brain and hypotelorism.

Figures 5, 6. 5 - Ultrasound examination at 25 weeks GA (Cervical transversal view) showing meningocele. 6 - 3D Ultrasound examination at 25 weeks GA of the face.  

Figures 7, 8. 7 - Postmortem view of the conjoined twins ("Twin Bâ€): anterior view. 8 - Postmortem view of the conjoined twins ("Twin Bâ€): posterior view.

Figures 9, 10. 9 - Postmortem view of the conjoined twins ("Twin Bâ€): left lateral view. 10 - Postmortem view of the conjoined twins ("Twin Bâ€): right lateral view.

Figures 11, 12. Postmortem view of the conjoined twins ("Twin Bâ€): meningocele view. 12 - Postmortem view of the conjoined twin ("Twin Bâ€): face.