So how do these cells get there and where did the rumor that women retain the DNA of every man they ever slept with start? The results were the first group who only had daughters had an 8% rate of male microchimerism. Because these cell lines from the fetus can survive for decades after the pregnancy, subsequent pregnancies a given woman has can then see some of these cell lines find their way into the new little. Demonstrating this cellular exchange, directly after pregnancy, approximately two thirds of women will carry fetal immune cell lines, for example. On the flipside, about 1/3 of the time the baby will have maternal immune cell lines after they are born.