Recently, an amazing mother from Texas, Cara Winhold, gave birth to two babies at the same who were approximately two weeks apart in age. The two babies are being called a miracle. How is this possible? Cara is one of the few women in the world to experience a phenomenon called “superfetation”. The word appears to have French roots and means “above” (super) and “fetus” (fetation). It refers to when a person has a new second pregnancy occur when the person is already pregnant. Typically, any efforts to get pregnant a second time would result in nothing happening to the first pregnancy and no new pregnancy occurring. But in this rare case, sperm entering the body of a person giving birth, fertilizes an available egg and begins a second pregnancy process. In this manner the person giving birth has two embryos growing that are different ages. The difference in age can be days or weeks. In Cara’s case it was about two weeks.
Process of Superfetation
How did this occur? Cara and her doctors appear to think that she ovulated twice and released two eggs that were fertilized at different times. Some experts refer to this as multiple ovulation. Others state that only one ovulation is occurring, and more than one egg or ovum is being released. The result is the same – a chance of more than one egg being fertilized. This can happen at the same time which leads to twins or at slightly different times leading to superfetation. Usually, the time period is quite close together. Thus, regardless of the time difference, when the babies are born they are considered “twins.” In Cara’s case, she was told at five weeks that she had only one child and a couple of weeks later that she had two kids. She viewed this surprise as a miracle because of her history of miscarriages before this pregnancy.
Superfetation can also occur and is actually more common in other species such as: fish, some horses, hares, and badgers. In humans most of the cases are associated with in vitro fertilization, which was not the case for Cara, making her pregnancy extremely rare. For women undergoing in vitro fertilization, medications being taken to stimulate ovulation will sometimes overstimulate the process and generate more eggs than normal. While this is useful in increasing the likelihood of these women getting pregnant or generating more eggs for them to fertilize, it can create challenges if the woman is impregnated by a partner and more than one of the eggs are fertilized at different times.
Risks of Superfetation
Some risks can arise from superfetation. The obvious risk is based on the age of the fetuses. The greater the difference between their ages is, the more likely there are concerns for the younger fetus being born too early. Often the babies are delivered very close in time as the womb’s environment changes substantially after birth and the babies need to be removed from it. If one of the twins is much younger, it may be a premature baby and have problems that are common for premature babies, such as: breathing complications, abnormally low birth weight, bleeding in the brain, movement and coordination problems, kidney problems, and infections. There are also challenges for people carrying multiple fetuses including: hypertension or high blood pressure, pregnancy diabetes (gestational diabetes), anemia, hearing problems, vision problems, preeclampsia, and more.
A natural question to ask if whether superfetation should be prevented. And the answer is “not really.” It’s nearly impossible to predict if a person is not engaging in in vitro fertilization. Most people do not know when they are producing more than one egg during a menstrual cycle because the cycle feels the same as always. Also, given the short amount of time between one egg being fertilized and a second being fertilized, some people do not know they are pregnant until well after superfetation occurs. That was the case for Cara who only found out after a second ultrasound. So, preventing it is unlikely. If a person is pregnant, not having sex a week after finding out might decrease the chances of superfetation occurring. But again it is so rare that such behavior is unlikely to be recommended by most clinicians. So, if you are one of the very lucky people to experience superfetation, work with your doctor to plan accordingly so that you have the healthiest outcome possible.