Every pregnancy is unique in its own way; some come fast while others take long to occur. Some babies are born early while others come on time. The variations are as many as the mothers. However, there is one form of pregnancy so unique that it continues to stir debate among scientists as to whether it is real or just a myth.
A few weeks ago, a man was notified that he had a child he did not know existed. The man apparently briefly dated a woman but they separated when she revealed that she was two months pregnant with another man’s baby. The woman later delivered a baby boy and two months later had a baby girl. She currently has two children; the 10 months old girl and the one-year-old boy. Both children were in the uterus at the same time but had different development stages. To confirm the babies’ paternity, deoxyribonucleic acid commonly known as DNA tests were done that confirmed they belonged to two different fathers.
Dr Victor Ogik, a gynaecologist at Seven Medical Doctors, describes the situation where a woman becomes pregnant a second time with another (younger) foetus in the face of an ongoing pregnancy as a case of superfetation. It occurs when an embryo from a different estrous cycle forms while another one or a foetus is already present in the uterus. It is common in animals but happens rarely in humans. It is possible when the woman has two uteri, or where the estrous cycle continues through pregnancy.
“Superfetation should not be confused with having twins or other forms of gestation since it involves the conception of an additional foetus during an established pregnancy. While twins are separated by a few minutes, with superfetation, the two foetuses develop at different rates and have different due dates,” Dr Ogik clarifies.
Dr Victor Ddamulira, a gynaecologist at Sevem Medical Doctors, notes that superfetation in humans is extremely rare and when it happens, it is always met with suspicion. He adds, however, that recently the phenomenon might be becoming less rare due to the increased use of fertility treatments.
A case published in 2005 in The Journal of Paediatrics, for instance, describes how a 32-year-old woman who had undergone embryo transfer later became pregnant with twins and one additional growth-discordant foetus. Initially, two out of the three embryos transferred to the woman’s uterus implanted themselves and a viable twin pregnancy was pronounced. The third embryo did not develop into a foetus.
However, a triple pregnancy was discovered around five months later, when a third smaller foetus was seen by ultrasound. This foetus was deduced to be around three weeks younger than its siblings. This led to the conclusion that there had been a subsequent fertilisation and implantation following the successful double implantation from artificial insemination.
“It sounds impossible, but it can and does happen, although it may happen only once out of several million pregnancies. The rarity could also be because some of the cases go undetected and thus unreported and some end up being mistaken for ordinary twin pregnancies. The babies are usually delivered at the same time as it is medically necessary in most cases to induce labour or to deliver them by C-section, but in development, one baby is older than the other and cannot be considered as twins,” he clarifies.
Recorded human cases
In May 2007, Harriet and Thomas Mullineux, conceived three weeks apart, were born in Benfleet, Essex, to Charlotte and Matt Mullineux. She had been told she was carrying twins, only to learn that one twin had been miscarried and was being reabsorbed by her body (an uncommon but not rare phenomenon known as vanishing twin syndrome). One of her early ultrasound examinations had revealed a small blob of tissue in addition to the twins, but no importance had been attached to the observation.
Mullineux was told to undergo another ultrasound a couple of weeks later, by which time it was clear that the little blob that had been observed in the previous ultrasound was growing into a baby.
In 2009, Todd and Julia Grovenburg of Fort Smith, Arkansas, received international media attention for Grovenburg’s conception of an additional child while already pregnant with a child conceived two and a half weeks earlier.
If it were possible to carry both children to term, the birth of the first child would be expected in December 2009, whereas the second child would be due in January 2010.
Both healthy babies were delivered through caesarean section on December 2, 2009. In 2015, Kate and Peter Hill, from Brisbane, Australia, conceived two baby girls 10 days apart. What makes this case rarer - the couple had only a single intercourse prior to the two conceptions.
Superfetation in history
According to research done by Prof Lawrence Omo-Aghoja of the Department of Obstetrics and Gynecology, Faculty of Clinical Medicine, College of Health Sciences, Delta State University, superfetation is much more common in the animal kingdom. Among mammals, it is well documented in badgers, buffalo, mink, and panthers but it is nearly unheard of in humans, which leads some to question whether it can reliably be said ever to happen at all.
Aghoja, further reveals that some scientists are still sceptical about whether superfetation occurs at all, and believe there must be some other explanation for cases in which it appears to have happened.
“First and most important, once a woman becomes pregnant, ovulation stops. After conception occurs in a normal pregnancy, the corpus luteum (and later the baby’s placenta) releases hormones that stop further ovulation. Also, the lining of the uterus thickens in a way that should prevent a second embryo from attaching itself. Finally, the cervix forms a barrier known as the mucus plug, which is designed to protect the developing foetus from microbes that might make their way into the uterus from the outside world. Just as it prevents microbial infection, the mucus plug is also an effective barrier to sperm,” he reveals.
For this rare reproductive abnormality to happen, ovulation must occur while a woman is already pregnant, sperm must somehow make it past the mucus plug and implantation must occur in a uterus that is no longer prepared for it. The oddity of all the above happening is what keeps fueling the debate whether superfetation in humans is possible.
With superfetation, the difference in the length of gestation between both foetuses can be large. In such a case, there is the risk that the younger foetus could also be delivered along with the older foetus. This means that the younger baby is born prematurely and the risks of a premature baby are applicable to it. However, all known cases of superfetation have been of twins that are between 10 days to three weeks apart, and the deliveries of both babies in these cases have been safe.
With previous cases of superfetation, the difference in age between the two babies was not established until the babies were delivered. Though the babies were born at the same time, one of them was technically born prematurely. The premature baby had to face all the risks associated with being premature.
If you think that you might have conceived at different times, then it is best that you discuss the same with your doctor as they will be able to conduct tests and determine if it is the case or not. The most important thing to remember is to stay calm. Medical technology has advanced enough to be able to plan for both pregnancies in order to ensure the health of both babies along with your own health.