In a rare case a northern Michigan woman with two wombs gave birth to twin daughters, one from each womb.

Sarah Reinfelder, 21, from Michigan in the U.S. gave birth to Kaylin Joy and Valerie Marie seven weeks prematurely by Caesarean section on Thursday at Marquette General Hospital in the Upper Peninsula.

She has a condition known as uterus didelphys, in which the womb develops in two parts, each with its own fallopian tube. Doctors said such twin births are rare.

Doctors said Kaylin Joy was delivered first and weighed 3 pounds, 15 ounces, while Valerie Marie weighed 4 pounds, 15 ounces. The doctors added that both the babies have not fully developed the use of their lungs yet though are otherwise healthy. They said the babies would probably be kept in hospital for up to a month and they and their mother are doing fine.

Reinfelder, her husband Shane and 10-month-old son William have been living in Marquette for about two months in order to be close to the hospital though they are originally from Sault Ste. Marie.

A case like Reinfelder’s is rare although there have been several other similar cases including that of a British woman, Hannah Kersey, of Northam, Devon with a double uterus who gave birth to triplets which was the first case of its kind. In 2006, Kersey gave birth to a pair of identical twins from an egg that had implanted in one womb and then split, and also to a baby from a single egg in the other womb. The chances of this kind of a birth are very rare, and have a likelihood of one in 25 million.