Carrying two babies, but they aren't twins? A woman goes in for her routine first sonogram where doctors see a healthy baby girl growing in the womb. Moments later, doctors hear a second heartbeat belonging to a younger fetus. They soon discover that the woman is pregnant with two children, two weeks apart in age, making them siblings, not twins.
An Arkansas couple appears to have a very rare case of superfetation, which involves conceiving while already pregnant. Doctors have only found about 10 other similar cases in history. While gross differences in the conception dates of the babies can potentially cause lung development issues in the younger one, these babies appear to be healthy and growing at normal rates. The babies have different due dates, but will likely be born at the same time. This should make birthday party planning a bit easier for the parents, because if they were born on their actual due dates, one would be born in December 2009 and the other in January 2010. Would you treat the children as siblings or twins?