Surrogate mom gives birth to twins boys, but one only was from her IVF cycle, the others was her own.
How is that possible?
When a couple uses a gestational carrier (what most people think of a surrogacy), embryos are produced from the eggs from the intended mother and sperm from the intended father. Sometimes the eggs or sperm are from a donor instead. Regardless, the embryos are placed in the womb of the gestational carrier, the woman who will carry the pregnancy and give birth for the intended parents. The carrier will take hormones to help prepare her uterus for pregnancy. This process has been done for years by fertility specialists, is highly successful and despite its complexity usually goes off without a hitch.
Not this time though...
A California woman agreed to be a gestational carrier for another couple. They did a form of IVF and the procedure seemingly went well. The carrier became pregnant and on ultrasound they saw twins. Since one embryo was transfered, the doctors naturally assumed the twins were identical. The pregnancy went well, the twins were delivered by cesarian section and went to live with the intended parents.
A month later, genetic testing revealed that the twins were not identical, and that the child's genetic parents were actually the gestational carrier and her husband.
How could this happen...
In a process called suprafecundation, a women who is already pregnant, or this case, in the process of becoming pregnant, can ovulate again.
When this happens, a woman who is pregnant would conceive a second pregnancy when she ovulates a month later. So, the second baby would be due a month later than the first. This type of event is exceedingly rare, but it looks like this is happened here, but on a shorter time frame.