Can You Get Pregnant While Pregnant?

Since you’re already pregnant, how can you get more pregnant? There’s no such thing as a double pregnancy, right? Unfortunately, it’s not that simple.

It is possible to get pregnant while pregnant; it’s called a ‘superfetation pregnancy.’ Women have experienced it, but it’s so rare that couples who go through it either make the news or carve their place in medical journals or both.

In 2021, Rebecca Roberts was pregnant with her first child for three months when sonography confirmed that she had another fetus growing inside her. She conceived the second baby three weeks after the first one.

“In theory, you can become pregnant while pregnant. It could explain why twins aren’t developing along the same growth pattern. A woman would need to have intercourse within the short window of ovulation, which usually happens within three days.”, claims Jane Frederick, MD, FACOG, HRC Fertility, an affiliate of Keck School of Medicine of USC.

A superfetation pregnancy occurs when another egg is fertilized and implanted in the uterus that is already growing a pregnancy. If this sounds unusual, you’re right; it is.

Superfetation is known to be common among mammals like rabbits, sheep, etc. But in humans, it’s extremely rare. In fact, only around 10 cases of superfetation are documented today.

The reason it is so rare is that when one egg is fertilized and growing in the uterus, it’s hardly possible for another egg to get fertilized by sperm. As the fertilized egg sticks to the uterine lining, this lining thickens and doesn’t leave space for another fertilized egg.

“Sperm is blocked from reaching the eggs in early pregnancy due to the mucus plug that forms in the cervix. This protective covering has bacteria and infection-blocking properties that work on sperm too,” says Dr. Frederick. “However, sexually transmitted diseases can still be passed while pregnant, so appropriate protection using a condom should be taken,” she adds.

Babies born via superfetation aren’t identical or unidentical twins. Superfetation occurs when two fetuses are conceived at different times. They have different gestational ages and grow at different rates.

Generally, a superfetation pregnancy does not have huge risks like miscarriage involved. During delivery, the second biological child could be born pre-mature, but with proper assistance from your medical provider and/or some time in the neonatal intensive care unit, a superfetation pregnancy can be navigated.

In 1999, a 38-year-old woman went through a superfetation pregnancy and delivered healthy babies four weeks apart.

In another case, a 32-year-old woman, in 2005, was pregnant with twins through IVF. A few weeks later, medical professionals discovered that she was pregnant with triplets. The third fetus was three weeks younger and was implanted by natural conception.

Dr. Frederick confirms, “If both fetuses are developing normally, there may not be any increased risks and have the same risks as carrying twins in general.”

While cases of a double pregnancy are rare, and it’s unlikely to become pregnant while pregnant, to be safe from sexually transmitted diseases, it’s advisable to use contraception.

Scientifically, when you’re pregnant, a mucus plug forms at the cervix that blocks infections and sperm. So usually, sperm doesn’t go inside your uterus. But in extremely rare cases, it can.

Ovulation after conception is highly unlikely since a fertilized egg is already growing inside the uterus. Generally, it’s not possible to have another implant in the uterus after one fertilized egg.