Can You Get Pregnant While Being Pregnant?

The idea of getting pregnant while already pregnant may seem strange, but it is possible in rare cases. This phenomenon is called superfetation and it occurs when a woman becomes pregnant a second time while still carrying the first pregnancy.

In this comprehensive guide, we will explore what superfetation is, what causes it, how common it is, the risks involved, how it is diagnosed and managed, and what delivery and birth is like with superfetation. We will also answer some frequently asked questions about getting pregnant while pregnant.

Read on to learn everything you need to know about superfetation and whether it is possible to get pregnant while already pregnant.

Key Takeaways:

  • Superfetation is when a woman becomes pregnant a second time while still pregnant with the first baby. It is very rare.
  • It occurs due to ovulation occurring during an existing pregnancy, often caused by a twin pregnancy or fertility treatments.
  • Risks include premature birth, low birth weight, and complications. Careful monitoring is required.
  • Diagnosis involves ultrasounds and testing to confirm different gestational ages.
  • Management involves close medical supervision and early delivery may be planned.
  • Delivery timing depends on the gestational ages of the fetuses and C-sections are common.

What is Superfetation?

Superfetation refers to the phenomenon when a pregnant woman conceives another baby while still pregnant with the first one, resulting in two fetuses of different gestational ages in the womb simultaneously.

This means the woman releases an egg that gets fertilized by sperm even though she is already pregnant. The second fetus conceived is younger than the existing one and lags behind in development.

Superfetation results in fetuses that have different due dates, since they were conceived at different times. For example, a woman may become pregnant with twins where one fetus is 12 weeks old and the other is 8 weeks old.

This is different from regular twin pregnancies where two eggs are fertilized at the same time during one ovulation cycle. With superfetation, ovulation and conception occur twice in separate cycles while pregnant.

How Common is Getting Pregnant While Pregnant?

Getting pregnant while already pregnant is extremely rare. Estimates suggest superfetation occurs in just 1 out of every 125,000 pregnancies.

Less than 10 cases of superfetation have been reported in medical literature. However, experts believe it may happen more often than we realize, since the second fetus conceived may not survive or may be reabsorbed by the mother’s body early on.

Superfetation is more likely to occur in the first trimester of pregnancy when ovulation and conception are still possible. By the 2nd and 3rd trimester, hormonal changes in the woman’s body prevent further ovulation and pregnancies.

What Causes Superfetation?

There are a few key factors that can lead to superfetation and getting pregnant while already pregnant:

  • Twin Pregnancy – Carrying twins makes superfetation more likely. This is because with two fetuses, the mother still ovulates and releases eggs due to higher levels of the hormone FSH.
  • Fertility Treatments – Use of fertility drugs or procedures like IVF can cause superfetation by stimulating extra ovulation.
  • Hormonal Imbalances – Problems with hormones like FSH and LH can lead to more than one ovulation while pregnant.
  • Genetic Predisposition – Some women may be genetically inclined to ovulate more than once per cycle.
  • Existing Health Conditions – Thyroid disorders, tumors, and other health issues may affect hormones and ovulation.

So in summary, the main cause is ovulation and fertilization occurring again while already pregnant. Women with twins or using fertility treatments are at a higher risk.

Risks of Superfetation

Carrying two pregnancies of different gestational ages can pose some additional risks and complications:

  • Premature Birth – The younger fetus may not be developed enough at birth if delivered based on the older fetus’ due date.
  • Low Birth Weight – The younger baby often has a lower birth weight since it has less time to grow in the womb.
  • Congenital Disorders – Higher odds of birth defects and disabilities due to premature delivery.
  • Pregnancy Loss – Risk of miscarriage or stillbirth is higher for the younger fetus.
  • Medical Complications – Issues like hypertension, diabetes, and preeclampsia are more common.
  • Developmental Issues – The younger baby may face cognitive or physical developmental delays.
  • Intrauterine Growth Restriction – The younger fetus may have growth problems due to lack of space or nutrition.

So pregnant women diagnosed with superfetation require careful monitoring and management to prevent complications. Let’s look at how it is diagnosed next.

Diagnosing Superfetation

Since superfetation is so rare, it often goes undiagnosed or is detected unexpectedly later in pregnancy. But there are a few ways doctors can confirm a double pregnancy:

  • Ultrasound Exam – An ultrasound that shows fetuses of very different sizes can indicate superfetation.
  • Ovulation Tracking – If ovulation occurred during pregnancy, superfetation is likely.
  • Hormone Levels – Certain hormone patterns can point to ovulation happening again.
  • Gestational Age Tests – Comparing fetal kidney development helps determine different gestational ages.
  • DNA Testing – Testing amniotic fluid or placenta tissue can confirm if fetuses have different fathers.

So combining ultrasound imaging, ovulation data, lab tests, and medical history allows diagnosis of superfetation. The fetuses must be at least 2-3 weeks apart developmentally.

Let’s discuss how superfetation pregnancies are managed next.

Managing Superfetation

If superfetation is diagnosed, carrying the pregnancy to term requires extra care and monitoring:

  • Frequent Checkups – More ultrasounds and prenatal visits to monitor both fetuses. Checking for any growth issues or complications[1].
  • Early Delivery – Delivery may be scheduled earlier at 35-37 weeks before complications can occur, especially if the younger fetus is struggling[2].
  • Steroid Shots – Steroids may be given at ~34 weeks to boost fetal lung development if early delivery is planned[3].
  • Inpatient Monitoring – Admission to hospital around 32-34 weeks for close observation in high risk pregnancies.
  • Bed Rest – Strict rest prescribed to prevent preterm labor and support fetus development.
  • Nutrition Optimization – Dietary changes to provide maximum nutrients and nourishment to both fetuses.
  • Anxiety Management – Emotional support and counseling to cope with a high risk pregnancy.

The main goals are to prevent preterm birth of the younger fetus while also avoiding complications like stillbirth. With careful monitoring and management, many superfetation pregnancies result in healthy babies born at term.

Delivery and Birth with Superfetation

When and how to deliver babies in a superfetation pregnancy depends on the gestational age of each fetus:

  • If the fetuses are close in age, a vaginal delivery may be possible around 37-39 weeks.
  • If fetuses are very far apart (4+ weeks), a c-section is often necessary to deliver based on the younger fetus’ maturity while avoiding stillbirth of the older one[4].
  • C-sections are common as they allow doctors control over the delivery timing for the high risk pregnancy[5].
  • Vaginal birth may have higher risks for the younger premature fetus but can still be an option in some cases[6].
  • The younger fetus is often admitted to the NICU after birth for close monitoring since it is likely premature.

So the delivery method and timing aims to balance the risks and minimize complications for both fetuses. Close postnatal care of the younger premature baby is needed as well.


Can you get pregnant while already pregnant?

Yes, it is possible but extremely rare to get pregnant again while you are already pregnant. This is called superfetation and happens when another egg is fertilized days or weeks after the first pregnancy began. It requires ovulation to occur again despite existing high hormone levels.

How rare is it to get pregnant while pregnant?

Only about 1 in 125,000 pregnancies involve superfetation, or getting pregnant while pregnant. Fewer than 10 cases have been reported in medical literature. It is an exceptionally rare phenomenon.

What week of pregnancy can you get pregnant again?

Getting pregnant again is most likely in the first trimester, within the first 12 weeks. This is because ovulation and conception can still occasionally happen early on before hormones completely prevent it later in pregnancy.

Can you have twins from different fathers while pregnant?

Yes, superfetation can result in twins or multiples that have different biological fathers if the woman had intercourse with more than one partner. The fetuses conceived weeks apart by different fathers may be fraternal twins born together despite having different gestational ages.


In summary, getting pregnant while already pregnant is possible in very rare cases, resulting in a complex superfetation pregnancy. While risks are higher, with comprehensive medical care and monitoring both fetuses can often be carried to term and delivered safely. Superfetation illustrates how remarkably flexible and adaptable the female reproductive system can sometimes be.