In 2006, Kate Hill was diagnosed with polycystic ovarian syndrome (PCOS), a hormonal condition that prevented her from ovulating, BBC reports. After hormone treatments, Kate and her husband Peter were delighted to find out that she was pregnant. 10 days later, they found out that she had conceived again!
Kate initially conceived twins, but one baby didn’t develop. Almost two weeks later, while pregnant, she became pregnant again. Even though Kate was pregnant, she had ovulated again, causing her to become pregnant one more time.
What makes the Hills’ case even more exceptional is the fact that they only had unprotected sex once. “My husband and I only had intercourse one time,” Kate said in an interview with Today Tonight. “His sperm stayed alive for 10 days to fertilize the second egg released.”
“Hole in one, maybe,” Peter quips.
Her doctor had to Google it. “I’ve never ever seen it before,” Dr. Brad Armstrong said. “[Her condition was] so rare that I could not find any literature in the medical review websites at all.”
The twins, named Olivia and Charlotte, arrived 2 days before Kate’s planned C-section date. The Hills are now planning their daughters’ first birthday party.
This phenomenon is called superfetation. Find out more on the next page.
What is superfetation?
This phenomenon is called superfetation. Superfetation occurs when an already-pregnant woman ovulates weeks into her pregnancy. The second egg gets fertilized, causing the pregnant to be pregnant with twins.
Superfetation is very rare because it isn’t supposed to happen. "Pregnancy hormones usually shut down a woman's system, making it impossible for her to ovulate during her pregnancy," obstetrician Connie Hedmark explains to BabyCenter. "This is why superfetation is so remarkable.” (This is totally different from superfecundation, which is when two eggs are released simultaneously and fertilized at separate times.)
According to Pregnancy Corner, only around 10 cases of superfetation have been documented in medical literature, and experts are suspicious even of some of these. But many experts also say that superfetation may be more common than we think, as some cases may be mistaken for ordinary twin pregnancies.
READ: Woman conceives while pregnant – superfetation
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