In a rare case of “foetus in foetu”, a baby boy in Mumbra in Maharashtra’s Thane district was born carrying his twin in his stomach, a radiologist told Scroll.in on Tuesday. After his birth on July 20, the child underwent a surgery on July 24 to have the foetus removed.

Dr Bhavna Thorat, a consulting radiologist at Bilal Hospital in Mumbra, noticed the abnormality when the 19-year-old mother was in her ninth month of pregnancy. “I saw some mass in the baby’s abdomen,” Thorat told Scroll.in. “The presence of some bones made me curious.”

After his birth, the baby boy underwent tests that revealed the mass in a sac in his abdomen. “Inside the sac, there was another baby with a head with a well-developed brain,” the radiologist said. “I got to see the lower limbs, and we think that the parasitic twin had grown up to 13 weeks and then stopped.”

She explained that in the foetus-in-foetu phenomenon, the baby in whom the twin grows is medically called the host baby, and the other is called the parisitic twin.

The newborn underwent an operation at the Titan Hospital in Thane on July 24. The mass in his abdomen weighed around 150 g. Both the mother and the baby boy are now in good health.

Doctors believe that the mother had conceived a monozygotic twin, and that during their development, one of the twins had entered the body of the other.