A boy has been born in Hong Kong with a fetus in his stomach in what doctors said was a rare case of "fetus in fetus" in which one twin becomes trapped inside another during pregnancy and continue to grow inside it.

Local media reported Thursday doctors carried out a scan on the boy's mother when she was in her 25th-week of pregnancy and noticed a "tumor" in the fetus's stomach. The "tumor", which was three to four centimeters in width, contained a torso and limb-like tissues. When the fetus grew, the "tumor" became larger as well. And in her 37th-week of pregnancy, the mother gave birth to a healthy boy weighing 3.4 kilograms. Ten days after the birth, doctors operated and removed the "tumor" from the boy's stomach. The boy is now recovering in a local hospital and will go home in 10 days, said the reports.

"It occurs in only every 500,000 live births," said Xu Peihua, an assistant professor in Hong Kong University. "And it occurs in Hong Kong only every 10 years."

(Xinhua News Agency May 18, 2007)