The Hanoi Obstetrics and Gynecology Hospital on Wednesday afternoon reported a rare case of identical twins with different phenotypes and genotypes, marking the first case ever known in Vietnam.

The 23-year-old woman is pregnant for the first time and conceived the twins naturally, according to Dr. Nguyen Thi Sim, director of the Center for Prenatal and Neonatal Screening Diagnostics at the hospital.

During her visit to the hospital during the 16th week of her pregnancy, doctors determined that the first fetus is female and has Turner syndrome (TS), also known as 45X or 45XO – a genetic condition in which a female is partially or completely missing an X chromosome. 

The second fetus is male and posseses the 46XY genotype.

Doctors terminated the pregnancy in agreement with the woman and her family because the female fetus was abnormally swollen and tests showed a high chance that it would be stillborn.

“Although the twins cannot be born, this is an extremely rare case which proves the possibility of identical twins with different phenotypes and genotypes,” said Dr. Sim.

According to medical literature, identical twins are most often identical in their phenotypes and genotypes and are nearly always same sex.

Therefore, the 23-year-old woman’s pregnancy is exceedingly rare.  

This is also the first known case in Vietnam, Dr. Sim noted during Wednesday’s press conference.

Sim said that the case has provided a completely new, deeper, and broader perspective on genetics and obstetrics and gynecology.

Commenting on the incident, Assoc. Dr. Tran Duc Phan, president of the Vietnam Medical Genetics Association, and Nguyen Duy Anh, director of the Hanoi Obstetrics and Gynecology Hospital, emphasized the importance of conducting scientific research and studies in order to ensure that people have normal pregnancies and healthy deliveries, especially in cases of multiple pregnancies.

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