First‐trimester diagnosis of conjoined twins after in‐vitro fertilization–embryo transfer (IVF–ET) at blastocyst stage

Conjoined twinning is a rare condition, occurring in 1 in 200 000 pregnancies1. Conjoined twins have been reported in association with in-vitro fertilization (IVF) and assisted hatching2 and intracytoplasmic sperm injection3, but not blastocyst transfer. We report a case of conjoined twins conceived after blastocyst transfer. A 36-year-old patient, gravida 0 para 0, was referred to us with primary infertility of 6 years' duration. Infertility investigations revealed no abnormal findings. On the seventh attempt at IVF–embryo transfer, five oocytes were extracted and incubated in human tubal fluid. Five embryos were fertilized and two were transferred at the four-cell stage on day 3. The excess embryos were cultured in sequential media (Sydney IVF Blastocyst Medium, Cook, Brisbane, Australia). One expanded blastocyst was transferred on day 5. At 14 days after the transfer of the four-cell embryos, a urine human chorionic gonadotropin test was positive. At 5 weeks' gestation, transvaginal sonography revealed one gestational sac in the uterus. Transvaginal sonography was then performed at weekly intervals. At 6 weeks, a fetal heart beat was detected. At 7 weeks, the crown–rump length (CRL) was consistent with gestational age but at 8 weeks' gestation, it was slightly shorter than normal. At 9 weeks' gestation, the CRL was notably shorter and the head of the V-shaped fetal mass (Figure 1) was smaller than the body. At 10 weeks' gestation, the fetus appeared to have either two heads or a cyst around the neck. Anencephalus, conjoined twins and hygroma were considered as differential diagnoses. Based on our findings, possible anomalies were conveyed to the patient and her husband and they finally opted for termination of the pregnancy. This was performed at 11 weeks' gestation by dilatation and curettage. Macroscopic examination of the aborted fetus revealed one head, four eyes, four limbs and two spinal cords (Figure 2). Microscopic examination revealed that the fetus had two ocular organs, two upper aerodigestive tracts, two intestines, two pancreases, two livers, two kidneys and two mesonephroi. Chromosomal examination of placental villi showed a normal female karyotype. Ultrasound image at 9 weeks' gestation demonstrating the V-shaped fetal mass. Postmortem photograph of the aborted fetus. Macroscopic examination revealed one head, four eyes, four limbs and two spinal cords. Assisted reproductive technology requiring manipulation of the embryo has been associated with monochorionicity4. Although it was not possible to prove that the conjoined twins in our case resulted from blastocyst transfer, the extended culture to the blastocyst stage could have been the cause. Recently, it was reported that blastocyst transfer increases the incidence of monozygotic twinning5, 6. It is assumed that monozygotic twinning and conjoined twinning result from mitotic division of the inner cell mass. It could be that monozygotic twinning results from complete division of the inner cell mass while conjoined twinning results from incomplete division, the mechanism being basically the same. The frequency of blastocyst transfer may increase in the future, because it makes possible a single embryo transfer and prevents multiple pregnancies. Thus the technique of extended culture of embryos could come into wide use, and the incidence of conjoined twins may increase as a result. While improving the technique of extended embryo culture and the composition of sequential medium may prevent the occurrence of monozygotic and conjoined twins, careful ultrasound examination should be performed after blastocyst transfer to exclude the possibility of conjoined twinning. Y. Shimizu*, J. Fukuda*, W. Sato*, J. Kumagai*, H. Hirano*, T. Tanaka*, * Department Obstetrics Gynecology, School of Medicine, Akita University, 1-1-1 Hondo, Akita 010-8543, Japan