Saudi Gazette report RIYADH — A medical and surgical team specialized in separating Siamese twins, led by Supervisor General of King Salman Humanitarian Aid and Relief Center (KSrelief) Dr. Abdullah Al-Rabeeah, who is also an adviser at the Royal Court, began an operation on Thursday morning to separate the Yemeni parasitic twins Aisha Ahmad Said Mheimoud. The surgery comes in the implementation of directives of Custodian of the Two Holy Mosques King Salman and is being performed at King Abdulaziz Medical City at the Ministry of National Guard. The surgery is expected to last for eight and a half hours with the participation of 25 doctors and specialists, in addition to technicians and nurses. Aisha is a complete baby with a parasitic twin sharing the pelvic area, in addition to having genetic defects and sharing of lower urinary and reproductive systems. Thursday"s operations is the 50th surgery performed so far to separate such twins as part of the Saudi National Program for the Separation of Conjoined Twins. Over three decades, 117 Siamese twins from 22 countries have been examined and assessed as part of the program. Parasitic twins, a specific type of conjoined twins, occur when one twin ceases development during gestation and becomes vestigial to the fully formed dominant twin, called the autositic twin. The underdeveloped twin is called parasitic because it is only partially formed, is not functional, or is wholly dependent on the autositic twin.