Can You Get Pregnant While Pregnant? – Superfetation

Can you get pregnant while pregnant?
Can you get pregnant while pregnant?

Can you get pregnant while pregnant already? This extremely rare phenomenon – superfetation- challenges our understanding of conception and pregnancy. It’s a rare occurrence that prompts curiosity about how and why it happens.

Is it serious? How does it affect your body during pregnancy? This article will give you all the knowledge you may want to know about superfetation. Let’s explore this remarkable topic together to unveil its mysteries.

Can You Get Pregnant While Pregnant? – An Overview

Getting pregnant while already pregnant is super rare phenomenon
Getting pregnant while already pregnant is super rare phenomenon

Getting pregnant while already pregnant – This might sound like something out of science fiction. But, this is a super rare phenomenon called superfetation. Now, let’s find out what it is and all related. 

What Is Superfetation or Double Pregnancy?

This rare phenomenon throws a curveball at the body’s typical pregnancy routine.  Your body throws up some roadblocks to prevent another pregnancy while one is underway.  But with superfetation, a new pregnancy manages to bypass these natural defenses.

How Rare Is Double Pregnancy?

Its occurrence in humans is extremely rare. The chances of you experiencing superfetation are exceedingly low, close to zero. Yet, superfetation was also discovered to occur in mammals, such as rodents and rabbits (Ochsner Journal – case report in winter 2021).

“It’s incredibly rare, and there aren’t many reports on this,” says Dr

Christine Greves, an OB-GYN in Orlando, Florida.  Scientific literature documented fewer than 10 instances by June 2021. Almost all known cases of double pregnancy involve assisted reproductive technology (ART).

Here is a typical example of double pregnancy over the years:

Jessica Allen embarked on a journey as a surrogate for a Chinese couple. During a routine ultrasound, it was revealed she was carrying twins. But, after the birth, both Allen and the intended parents were surprised by the babies’ distinct appearances. The following DNA testing uncovered a remarkable truth. One was the biological baby of Allen and her husband. The other belonged to the Chinese couple. 

Superfetation vs. Twins: What’s The Difference?

Getting double pregnancy is different from getting twins.
Getting double pregnancy is different from getting twins.

We’re probably all familiar with twins, whether identical or fraternal. Identical twins occur when a single fertilized egg splits in 2 after implantation with identical genetic makeup. Fraternal twins happen when two separate eggs are fertilized by different sperm at the same time.

Unlike twins, superfetation involves 2 separate pregnancies. A new embryo begins to develop while another pregnancy is already underway. This means the 2 fetuses have different conception dates. In short, it’s very difficult for you to tell the difference.

Superfecundation vs. Superfetation

Also known as heteropaternal superfecundation, this is another super rare pregnancy phenomenon. This phenomenon results in fraternal twins having the same mother and different fathers.  

It occurs when a woman releases 2 eggs during the same ovulation period, and each egg is fertilized by sperm from different partners. The result? The babies will be born to the same mother but different fathers at the same time.  

As of 2018, a paper published in the journal Forensic Science International documented only about 18 confirmed cases.1

What Prevents You From Getting Pregnant While Already Pregnant?

Hormonal Shifts:  One key change is the suppression of ovulation. Thus, ovulating during an existing pregnancy is highly impossible.

Cervical Seal: During pregnancy, a thick mucus plug forms in the cervix, creating a significant hurdle for sperm to overcome. This makes it much harder for sperm to reach the fallopian tubes, where fertilization typically occurs.

Unreceptive Lining: Even when a second embryo is formed somehow, your hormones will prevent it from implanting in the uterine lining.

Can You Get Pregnant While Pregnant – Symptoms & Causes

Chance of getting pregnant while already pregnant is likely impossible.
Chance of getting pregnant while already pregnant is likely impossible.

Although the chance of getting pregnant while you’re already pregnant is very rare, it’s still useful to learn more about its causes and symptoms.

What Happens In Double Pregnancy?

Normally, during your menstrual cycle, an egg is released and ovulation occurs. If fertilization happens, the fertilized egg implants in the endometrium, leading to pregnancy.

However, in superfetation, a second fertilization would occur while another pregnancy is established. This is unlikely because of hormonal changes that occur during pregnancy preventing a new pregnancy.

How Can You Get Pregnant While Pregnant?

Due to its extreme rarity, the exact causes of superfetation remain somewhat of a scientific mystery. Researchers haven’t been able to gather enough data to pinpoint definitive triggers. 

However, some clues point towards a possible link with ART, IVF, artificial insemination, and surrogacy. Take the example of a case of taking medications to stimulate ovaries during artificial insemination treatment. This may cause an ectopic pregnancy.

It’s important to remember that even with ART, superfetation is still highly unlikely. The body’s hormonal and physiological changes during pregnancy are very effective at preventing another pregnancy from taking hold. 

What Are The Symptoms Of Superfetation?

There aren’t any unique physical signs or symptoms that specifically point to it.

Diagnosis and Tests Of Superfetation

Diagnosing superfetation can be tricky because it can mimic other conditions involving twins. A routine obstetric ultrasonography might reveal 2 or more fetuses in the womb. But it alone isn’t enough to confirm superfetation. 

Some researchers believe the reasons may be placental insufficiency and unequal nutrient sharing.

The misdiagnosis also may be the cause of an ultrasound error involving a single fetus and twins. And then, this mistake could be changed to superfetation when the second embryo is discovered. 

How Is Superfetation Managed?

You can plan C-section for best delivery when getting double pregnancy
You can plan C-section for best delivery when getting double pregnancy

In case a fetus can develop more rapidly than the other, the younger one might face the possibility of premature birth. The doctor may recommend a C-section to optimize the chances of successful delivery. 

Your kids will be close in age. You can schedule your birth delivery somewhere between the older and younger babies’s estimated due dates.

What Should You Expect If Getting Double Pregnancy?

You will expect to experience a healthy pre-med pregnancy. The age difference between the fetuses is often 2 to 4 weeks2. This highly increases the chances of a healthy delivery for both. You can rest assured because the doctor can advise the most suitable time for a birth delivery.

Beyond that, the delivery process shares some potential risks associated with many carrying. These risks can include preterm delivery,  preeclampsia, low birth weight, and others. 

We can say, superfetation is a fascinating but incredibly rare phenomenon. While the odds of experiencing it are extremely low, understanding it is valuable knowledge.

  1. ScienceDirect – Forensic Science International – Volume 327, October 2021, 110948: Heteropaternal twinning: Unique case of opposite-sex twins with different fathers ↩︎
  2. NIH – National Library of Medicine – National Center for Biotechnology Information, Reprod Fertil Dev. 2013;25(7):1012-9. doi: 10.1071/RD12238: Unpredicted ovulations and conceptions during early pregnancy: an explanatory mechanism of human superfetation ↩︎

Lynn Campbell
Lynn Campbell

Lynn Campbell brings decades of experience as an editor for top newspapers, magazines, and websites. She learned to use credible sources and spot pseudoscience. Lynn is a writer, editor, copy editor, and researcher who has worked as copy chief at SPIN, ELLEgirl, and Kinfolk magazine, among many others. She has managed copy and research departments and served as a managing editor, deputy editor, staff writer, parenting editor, and advertising manager. Lynn also served as the copy chief for several books, including the New York Times best-seller The Kinfolk Home. She earned a Bachelor's degree in English literature from the University of Georgia. As a mother, Lynn combines her professional expertise with her parenting experiences to offer valuable insights to her readers.

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