An American woman who has a rare health condition wherein she has a heart-shaped uterus has given birth to twins, marking a one-in-500-million birth, as per reports. Only four in every 1,000 women have a heart-shaped uterus or a bicornuate uterus. The babies were born to 25-year-old Karen, who said, "I was monitored closely because it was a high-risk pregnancy."