The Telegraph newspaper said Thomas and Nathaniel Spence-Hamblin suffered from a condition called twin-to-twin transfusion syndrome, which meant blood vessels in their shared placenta were attached to each other.

If left untreated, one baby would have received too much blood while the other would not have had enough.

The surgery was very risky, with at least one fetus failing to survive in most cases, the newspaper said.

The boys, however, were born healthy Sept. 26.