A family in the UK has been making headlines around the world because of a rare case of superfetation twins. Parents Rebecca Roberts, 39, and Rhys Weaver, 43, have been trying to conceive for a year when they got pregnant with their first child.

According to CNN, Rebecca's first sonogram confirms her pregnancy of only one baby based on the sonogram. It is a baby boy that they named Noah.

However, at three months of pregnancy, the doctor suddenly found an unexpected little twin sister for Noah, which they named Rosalie.

"I got pregnant whilst I was already pregnant, which was absolutely crazy ... because that's not supposed to happen," Rebecca said to CNN.

Superfetation Twins: Conceived Three Weeks Apart But Born on the Same Day
(Photo: Wikimedia Commons)
Fraternal Twins

Superfetation: Rare Event of Getting Pregnant While Already Pregnant

Superfetation is an extremely rare case of a pregnant woman conceiving for the second time with a younger fetus, according to medical journalist and writer Melissa Conrad Stöppler, MD via MedicineNet.

The condition is characterized by the fertilization of a second egg cell in a uterus that already has an existing embryo. This condition is different from twinning or multiple gestations because superfetation involves two fetuses that have different gestational ages and due dates and occurs in animals but rarely in humans, with only ten cases reported in the medical literature.

In Rebecca's case, Atlanta gynecologist Dr. Lillian Schapiro explained that the egg was fertilized during first ovulation and somehow she ovulated again during that same cycle leading to another egg being fertilized. However, the two embryos are implanted at different times.

Schapiro added that a second embryo may have managed to attach itself and grow at a stage that doctors may not have thought possible, noting its rarity.

Since the couple has been trying to conceive for a year, her doctor advised a treatment in which Rebecca only took one dose of fertility drugs that stimulate ovulation. This could have aided the rare occurrence but Rebecca believes that this might just be a "medical marvel."

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Superfetation Twins: Noah and Rosalie, How are They Now?

Rebecca has constantly been sharing her super twins on Instagram, documenting their growth. According to The Hill, Rebecca had a Caesarian section on September 17, 2020, and delivered Noah and Rosali on the same day.

Noah was the oldest among the super twins by two minutes, weighing 4 pounds and 10 ounces. While Rosalie was born weighing 2 pounds and 7 ounces.

Since both babies are born prematurely, they were taken to the neonatal intensive care unit. However, they did not stay in the same NICU.

Rosalie was in a separate facility 15 minutes away from where Noah was placed. Since Noah was three weeks older he spent lesser time in the NICU for only three weeks, while little Rosalie spent 95 days.

Proud parents, Rebecca and Rhys said that at seven months the twins have been showing a lot of differences already. Although smaller than her brother, Rosalie is a little trooper and got her own personality.

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