Can Triplets Be Different Sexes? Here’s What Really Happens in the Womb

Human reproductive science is full of curiosities, but one of the rarest and most intriguing may be triplet—count ‘em: three—births.

Multiple births, such as triplets, occur far less frequently compared to single or twin births. In 2023, only 73.6 in 100,000 births were triplets according to the CDC. While there’s no data on how many of these were identical vs. fraternal triplets, it’s more common for triplets to be of different sexes. When triplets are all the same sex, they may be identical—which is one of the least common types of pregnancies in the world.

While fascinating, the truth is that having a triplet pregnancy can be dizzying: Prenatal to-do lists compound, prenatal checkups dominate the calendar, and expecting parents are often confronted with some anxiety-provoking medical concerns. At times, a triplet pregnancy can increase the level of care needed across the board.

That said, there’s also plenty to look forward to, and understanding the chances of triplet pregnancies can be an opportunity to appreciate the rare biology behind having 3x more to adore.

How are triplets conceived?

To understand how someone ends up with three babies at once, let’s take it back to square one of pregnancy: fertilization.

From this vantage, there are three different types of triplet pregnancies:

1. Monozygotic triplets – In this case, a single egg is fertilized by a single sperm—seemingly simple enough. Then, the fertilized egg splits into three, creating three identical babies: all the same sex, all with the same DNA.
2. Dizygotic triplets – In this scenario, two eggs are fertilized by two different sperm. One egg splits to form identical twins, while the other egg remains fraternal. Here, two babies will be the same sex, while the third could be the same or different.
3. Trizygotic triplets – The most complex of all cases, trizygotic triplets involve a multiple pregnancy where three eggs are fertilized by three different sperm. Each baby has unique DNA and may be different or the same sex. When triplets are of mixed sexes, it’s typically because they’re trizygotic triplets.

Another important distinction to make, especially for its medical implications, is how many placentas and amniotic sacs carry triplets in the womb. In this regard, there are three other types of triplets worth knowing about:

• Monochorionic, where all three fetuses share a placenta and gestational sac.
• Dichorionic, where two of three fetuses share a placenta and gestational sac. The third fetus has its own.
• Trichorionic, where each fetus has its own placenta and sac.

When one or more babies share a placenta, it can make it harder for the babies to mature in utero—babies may have different rates of development, or they may receive unequal amounts of nourishment.

No matter the type, all multiple pregnancies are considered high-risk, which means they need to be more closely monitored by healthcare providers. That said, it’s certainly possible to carry three babies to term safely, following the protocols prescribed by your OBGYN and care team. Learn how to choose an OBGYN you trust to ensure you feel comfortable and taken care of during this time.

How do triplets wind up with different sexes?

So, can triplets be different sexes? The answer is yes, and understanding the ins and outs of triplet sex is a lesson in how babies are conceived in the first place. Remember, sex is determined by the sperm (or trio of sperm) that successfully fertilize an egg:

• Sperm that carry an X chromosome result in a female
• Sperm that carry a Y chromosome result in a male

So, if you learn that two of your babies are girls and one is a boy, two scenarios are possible:

1. Two sperm—one carrying an X chromosome and the other a Y chromosome—fertilized two different eggs. Following fertilization, the X-carrying sperm split into two future females.
2. Three sperm—two carrying an X chromosome and the other a Y chromosome—fertilized three eggs, resulting in a female, another female, and a male.

If your triplets are identical, all will be the same sex—never a mix. On the other hand, even if every triplet is the same sex, they aren’t necessarily identical. Genetic factors can produce separate appearances and characteristics between siblings.

Identical and fraternal triplets: key characteristics

Beyond sex, there are some other traits that distinguish fraternal and identical triplets:

• Genetic makeup – Identical triplets share all of their DNA because they stem from the same egg, which split into three embryos. Fraternal triplets come from two or three separate eggs and sperm, which means they’ll share about half their DNA (similar to any other siblings).
• Appearance – Identical triplets (and twins) tend to look very visually similar. Fraternal triplets tend to look more different, but you might notice some clear similarities, like in any other family.
• Placenta and amniotic sacs – Identical triplets may share a placenta or sac depending on when the egg splits. Fraternal triplets, conversely, always have distinct placentas and sacs, though these can sometimes fuse in utero.

What does a triplet pregnancy feel like?

There are distinctions to be drawn between fraternal and identical triplets in terms of genetic makeup and its expression. But the experience of a triplet pregnancy is fairly aligned, no matter what “type” of triplets you’re having.

Some common symptoms of a triplet pregnancy include:

• Heightened fatigue – Because the body is working three times as hard, it’s common for parents undergoing a multiple pregnancy to feel more tired than they might with a singleton pregnancy.
• Heightened pregnancy nausea – Nausea and vomiting during pregnancy, also known as “morning sickness,” could feel more severe than in a singleton pregnancy.
• Bigger belly –Triplet and twin pregnancies typically cause the uterus to expand more than it would for one baby. Abdominal changes might also occur more quickly (you might affectionately call this faster-growing belly your “speed bump”).
• Shortness of breath – Because triplets take up more space, some expecting parents experience more pressure on their lungs, which can make it harder to take a full breath.
• Back pain – More babies can be a heavy load. This often results in added back pain, especially in the lumbar spine.
• Digestive complaints –Heartburn, constipation, and indigestion may become more common as the uterus continues to expand.

Additionally, it’s normal for triplet babies to be born before full term. On average, triplets are born between 32 and 35 weeks of gestation (in singleton pregnancies, full term is between 37 and 40 weeks).

Approaching their due date, triplet parents are highly encouraged to take it easy and watch for signs of early labor. Also important during this time is limited physical activity, more hydration and rest, and booking additional prenatal appointments to ensure an optimal labor and delivery process.

Who’s most likely to have a triplet pregnancy?

Remember: Triplet pregnancies are rare, with identical triplets being the rarest of the bunch. However, they tend to be more common if:

• Your pregnancy was supported by treatments like in vitro fertilization, when more embryos may be planted for possible fertilization.
• You underwent fertility treatment using ovulation-stimulating medications, which yield more eggs viable for fertilization.
• You have a family history of multiple births (however, only fraternal sets run in families—identical sets don’t!).
• You’re of advanced maternal age (over 35 years old).

Triplet pregnancy checklist: what to prioritize when you’re carrying three

Many future parents can feel both exhilarated and overwhelmed when they learn they’ll be toting three bundles home from the hospital. Just as there are numerous things to avoid while trying to get pregnant, it’s crucial to take precautions for the pregnancy itself. Having a clear plan of action to start the first trimester can help ground the excitement and prepare you for the journey ahead:

• Consider a multiples specialist – Many parents of multiples see a maternal-fetal medicine (MFM) specialist (or perinatologist), who focuses on high-risk pregnancies. MFM specialists can provide prenatal counseling, administer prenatal care, and assist with labor, delivery, and postpartum recovery.
• Clear the decks for more prenatal check-ups – It’s not always the case, but having multiples usually means booking more prenatal check-ups to monitor babies’ growth and watch for potential complications. If you work a 9-to-5 or have prior commitments, it might be helpful to communicate with your employer or community so you have all the time you need to make those appointments.
• Familiarize yourself with high-risk pregnancies – One of the difficult parts of being pregnant with triplets is the potential for certain health risks. Anemia, hyperemesis gravidarum (severe pregnancy nausea), preeclampsia, and preterm labor are just some of the most common complications triplet parents may experience.

While these can sound scary, learning about how they’re treated—as well as signs and symptoms to watch for—can help you feel prepared and more reassured if they develop.

It takes a village to raise a child, and where triplets are concerned, there is no shame in needing a little more help. Twins, triplets, or even quadruplets can all benefit tremendously from a community that offers emotional and practical support. You’re encouraged to reach out to friends and loved ones who can pitch in with both prenatal prep and postpartum care; support groups can also provide more understanding through experience.

At the end of the day, triplet pregnancies require a little more of everything—hydration, physical rest, and emotional support. The triplets journey is a big one, but taking it all one step at a time can help you feel more confident when it’s finally time to meet your new favorite trio.

Learn about all things pregnancy with the SneakPeek® test

Can you use the SneakPeek® Early Gender Test if you’re expecting triplets? Yes! The SneakPeek Test lets expecting parents discover their baby’s predicted sex sooner. When looking at SneakPeek vs. competitors, it boasts over 99% clinically proven accuracy. The test works by analyzing the mother’s blood sample for the presence of male DNA. If male DNA is found in a triple pregnancy and you’re expecting identical triplets, all three babies are predicted to be male. For fraternal triplets, the presence of male DNA means you’re likely expecting at least one boy, if not more! If no male DNA is found, you’re likely having three baby girls.

Try the #1 OBGYN-recommended at-home early sex prediction test by ordering yours today.*

*SneakPeek recommended six to one among 100 OBGYNs survey

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