Superfetation in Surrogacy Explained

A recent California surrogacy case is making headlines, largely due to the uniqueness of this situation. The buzzword being thrown around is “superfetation.” What is this obscure term and how did it lead to an unusual situation for a surrogate and intended parents? On this page, we’ll explore what superfetation is, how it occurs, and what parents and surrogates can do to avoid some of the heartache associated with it.

Background of the News Story

The story goes back to 2016, and begins like most others do. A warm-hearted woman with a family of her own decided to help another family grow. She already had her own children and was happy to help, but also was excited because doing so would allow her to become a stay-at-home mom and save for a new house. She happened to be white and her husband black; the relevancy of this comes up a bit later in the story. As luck would have it, she was matched with a Chinese couple who wanted a baby, but couldn’t have one of their own. The team made an agreement and the surrogate went through the process. Ultimately, a single embryo was transferred and it developed normally.

Much to their surprise, however, later ultrasounds showed that the surrogate was carrying not one, but two babies. Twins! Everything continued to progress normally throughout the pregnancy and eventually two healthy babies were delivered. The surrogate reports that her contract expressly noted she was to have one hour with the babies after they were born, but because they had to be transferred to the NICU immediately after the c-section, she didn’t get the chance to meet them.

A couple months down the road, the intended mother sent the surrogate a photo of the babies. Indeed, both were healthy and well, but something struck the surrogate as odd. One baby clearly looked to be of Asian descent, while the other appeared to be of mixed race. That’s not unheard of with fraternal twins, or babies created with two eggs, but only one embryo was transferred. That means the babies should have been identical twins, made from the one embryo after it split. These babies should have looked exactly the same, but they didn’t. The surrogate began to ask questions, which ultimately led to the children being DNA tested. Indeed, the mixed-race child was not biologically related to the intended parents nor his womb-mate, but was the child of the surrogate and her husband.

Superfetation Explained

Under normal circumstances, a woman will only release one egg per month. Sometimes she’ll release two, which is why fraternal twins exist, and sometimes that egg will split, which is why identical twins exist. With fraternal twins, each baby has his own amniotic sac, while identical twins will share one. Even when IVF is used and multiple embryos are transferred, they respond more like fraternal twins; each baby develops in his or her own amniotic sac unless one of the embryos splits and becomes identical twins.


A woman’s body has several mechanisms in place to ensure this is how things occur. First, once a woman becomes pregnant, her body gets a hormonal signal to stop ovulating. No egg means there’s nothing to fertilize. Secondly, the woman’s cervix closes up with a mucus plug, which means sperm cannot get into the uterus. Lastly, an embryo can only implant itself into the uterus under very specific hormonal conditions. When a woman isn’t fertile or is already pregnant, the hormone balance is off and implantation cannot occur.


However, in very rare cases (roughly only 10 cases are on record with humans), a pregnant woman can defy all the odds and these checks the body has put in place and, while pregnant, can conceive and carry a second child. This is called superfetation. It’s one of the reasons why most contracts require surrogates to abstain from sex or use a barrier method during at least the early stages of the process. In this case, the surrogate did use a barrier method, but it failed. Ergo, she was not only pregnant with the baby conceived through the surrogacy process, but also with one created by herself and her husband.

Avoiding Superfetation Heartache

What ultimately happened in this case is that the intended parents did indeed return the baby to his biological mother and the surrogate of their baby. The intended parents are remaining private about the matter, but one can only imagine how hard this has been on everyone involved. Surely, for the parents who desperately wanted children, and also for the surrogate who was unprepared to give up a child of her own, though was glad to carry one for the couple.

One way surrogate teams can avoid this is, first, to be aware of the existence of superfetation. Simply in knowing about it, the surrogate can make the choice to abstain during the initial stages of surrogacy. Secondly, it can be written into a contract that the surrogate be expected to abstain. It’s important to note that clauses like this can seem incredibly intrusive to the surrogate, so if this is included in the contract, it’s important that she understand why and what the value to abstaining is. Given that surrogates choose this path to help a family and do not presently want more children of their own, most will gladly comply with a policy such as this because it protects them too. Furthermore, having a discussion about superfetation and what a team will do if it occurs, then including that in a contract, can add peace of mind as well. Everyone may agree to DNA testing after the birth, a surrogate may agree to relinquish rights, or any number of agreements can be made. The main point is that everyone should be on the same page prior to undergoing any procedures.

It’s also worth noting that, in this particular case, the medical team noted the babies were in two different amniotic sacs, but somehow it never registered with anyone that this alone meant the twins were not identical. Even during the pregnancy, and before DNA testing, an aware professional could have surmised something was amiss. Nobody did. Continuity of care by the medical team may not have prevented this, but it could have potentially alerted the team of the issue before the babies were born, giving them time to come to a consensus and cope with the change before the babies arrived.

Work with a Dedicated Surrogacy Team

It’s worth noting that EDSI was not involved in this case in any way; we were neither the agency who helped the couple, nor the surrogate, and don’t have information on this case beyond what has been mentioned in media outlets. Our hearts certainly go out to all parties involved in this difficult and rare situation.

That said, working with a team who understands the nuances of surrogacy and is there to help all parties throughout the process—even after a baby is born—is essential in ensuring the process is smooth for everyone. If you’d like to grow your family with the help of a surrogate, call EDSI at (213) 423-7997 or message us online for more information. If you’re a woman interested in becoming a surrogate, review the requirements and get in touch when you’re ready.



Tags: , , , ,