Expecting Mono Mono Twin Girls: How To Navigate A High-Risk Pregnancy

If you’re an expectant parent, twins often come as a delightful surprise. But when you discover that your twins are mono mono, meaning they share the same amniotic sac and placenta, it’s a mix of thrilling and nerve-wracking emotions. That’s precisely the rollercoaster of feelings my husband, Dave, and I experienced when we learned we were having mono mono twin girls.

Mono mono twins are rare, accounting for only 1% of all twin pregnancies. So, gaining a thorough understanding of what to expect while you’re expecting them becomes crucial.

But before we dive into all the ins and outs, let me share a wild and crazy story with you.

My Surprise 18-Weeks Pregnant Ultrasound

Savannah, Our ultrasound technician, caught us off guard when she casually said, “You know you’re having twins, right?”

Wait, what?! Talk about a jaw-dropping surprise!

Let’s rewind a bit. Until then, Dave and I were under the impression that we were in for the parenting ride with just one baby. I mean, we’d seen the little one on our 7-week ultrasound, and only two weeks ago, at our baby reveal party, we discovered it was going to be a girl.

To claim that we felt shocked would be the understatement of the century! We confidently sailed the one-baby ship for nearly half of my pregnancy!


Now that Dave and I have almost passed out (thanks, Savannah!), all the questions flooded in…

  • What are mono mono twins?
  • What are the high-risk complications?
  • What are the next steps?

You may think the same things we did, so let’s get to it. Here’s what you need to know about mono mono twins.

What Causes Mono Mono Twins?

Mono mono twins arise when the embryo refrains from splitting until after the formation of the amniotic sac, typically occurring around the 12th day of development following fertilization and the commencement of division.

In most cases, the embryo will split into two separate amniotic sacs within a few days. But in some cases, the splitting process happens slowly or not at all. As a result, the twins share the same “everything”—the amniotic sac and placenta.

Understanding Mono Mono Twins

To reiterate, Mono mono twins, often called “mono-mono” or “MoMo” twins, are identical twins who develop within a single amniotic sac and share a placenta. This term, short for “monoamniotic-monochorionic,” signifies the presence of a single chorion (the outer membrane surrounding an embryo) and a single amniotic sac (the fluid-filled enclosure containing the fetuses).

This remarkable occurrence is exceptionally rare and comes with inherent risks, primarily related to cord entanglement and other potential issues. Consequently, a pregnancy involving Mono Mono twins is classified as high-risk.

Now, let’s delve into the specifics of these potential complications.

Complications Associated With Mono Mono Twins

Because they share the same amniotic sac, mono mono twins are at a higher risk for complications than other types of twins. These risks include:

Intrauterine Growth Restriction

One or both twins may experience intrauterine growth restriction (IUGR), which can lead to problems with organ development and low birth weight.

Intrauterine growth restriction (IUGR) may impact any baby during pregnancy, but it is most frequently observed in babies born prematurely. IUGR occurs when the baby’s body or organs do not grow as expected. This may be due to problems with the placenta, the mother’s health, or the baby’s genes.

In some cases, medical intervention, such as steroid injections, may be necessary to treat IUGR. These injections help speed up fetal lung development to prepare for an earlier delivery.

Twin-To-Twin Transfusion Syndrome (TTTS)

This occurs when blood vessels in the shared placenta connect the twins’ circulatory systems. As a result, one twin may receive more blood and nutrients than the other, leading to unequal growth rates.

If TTTS is diagnosed early enough, laser surgery is an option to seal off the abnormal connecting blood vessels in the placenta to stop the harmful sharing of fluids. It involves making small incisions in the placenta to allow for better blood flow between the twins. The goal is to hopefully reverse or stop TTTS. However, even with treatment, there is no guarantee that TTTS will not recur.


In rare cases, one or both twins may pass away in utero due to complications like a cord accident, twin-to-twin transfusion syndrome, or IUGR.

Premature Birth

Mono mono twins are more likely to be born prematurely than other types of twins. In many cases, spontaneous preterm labor occurs between 26 and 28 weeks. As a result, most of these rare types of twins are born via c-section and spend time in the NICU (Neonatal Intensive Care Unit).

At least, this was the case with us.

Our mono mono twin girls were born early, at 27 weeks, via emergency c-section.

My husband and I chose for me to go inpatient at 24 weeks for continuous monitoring. I’m so grateful we did because our nurse caught a cord accident while I was on the monitor, saving both of our girls’ lives!


What To Expect

If you’re pregnant with mono mono twins, you’ll be monitored closely by your healthcare team due to your high-risk pregnancy. You can expect to have more of these things happen than other pregnant mamas:

  • Detailed ultrasounds
  • Non-stress tests
  • Frequent prenatal visits
  • Scheduled c-section (usually around 32 weeks)

You may sometimes be referred to a high-risk obstetrician or perinatologist—a doctor specializing in high-risk pregnancies.

My High-Risk Pregnancy Experience

Once Dave and I found out at 18 weeks that we were having mono mono twin girls, our world completely changed.

I was overseen by a high-risk team at Riverside Hospital, where I delivered our girls.

My OBGYN became “second” in the chain of command. Riverside Hospital called the shots, and my OBGYN followed their lead.

We went to ultrasounds every two weeks.

After our 18-week ultrasound, I was scheduled routinely every two weeks to check the girls’ heart rates and blood flow. The good news is with mono mono twins; you get to see your sweet babies MORE often!

One thing that never came up for me was to take a non-stress test. If you are interested or have questions, talk to your healthcare provider about this.

I went inpatient at 24 weeks for continuous monitoring.

If you live in the United States, you can check inpatient anywhere from 24 to 28 weeks to monitor your twins’ heart rates and blood flow. I highly recommend checking in at 24 weeks and being on the monitor as much as possible (I did this for up to 8 hours a day, sometimes more). The monitor is what saved Lua and Lily Mae’s life.

Mono mono twins 24 to 28 weeks are considered a “danger zone.”

I understand mental health is important too, but try to monitor your babies often throughout the day and night. If you think about it, it’s such a short period of time to be on the monitor versus a lifetime of love that awaits you with your precious ones!


The “Danger Zone” Period

The period between 24 to 28 weeks of pregnancy is often called the “danger zone” for mothers carrying mono mono twins.

The babies are rapidly growing during this time, and the risk of cord entanglement in their shared amniotic sac becomes more pronounced. This heightened risk necessitates close and vigilant monitoring by healthcare professionals to ensure the safety and well-being of both the mother and the developing twins.

It’s crucial to be acutely aware of this critical phase and follow medical guidance meticulously to minimize potential complications.

5 Crucial Tips On How To Navigate A High-Risk Pregnancy

1. Early Prenatal Care

When expecting mono mono twins early and regular prenatal care is your best ally. Schedule your first appointment with a healthcare provider experienced in high-risk pregnancies. They will closely monitor your progress, focusing on the health and growth of both babies. Be prepared for more frequent check-ups and ultrasounds to monitor their development closely.

2. The Importance of Nutrition

Proper nutrition is crucial during pregnancy but even more vital when carrying mono mono twins. You’ll need extra calories, protein, and nutrients to support the healthy growth of both babies. Speak with your OBGYN about this or consult a registered dietitian or nutritionist to create a personalized meal plan that meets your needs.

3. Stay Active and Rest

Maintaining a balance between staying active and getting enough rest is essential. Light, regular exercise can help improve circulation and reduce the risk of complications. However, always consult your healthcare provider before starting any exercise routine during a high-risk pregnancy. On the flip side, prioritize rest and relaxation to manage stress and avoid unnecessary strain.

4. Monitor for Complications

High-risk pregnancies, like those with mono mono twins, have a higher chance of complications. Keep a close watch for signs of preterm labor, preeclampsia, or other potential issues. Promptly report any unusual symptoms to your healthcare provider, as early intervention can significantly affect the outcome.

5. Prepare for the Birth

As you approach the final stages of your pregnancy, discuss your birthing plan thoroughly with your healthcare team. Due to the increased risks, you might need to deliver your mono mono twins via cesarean section. Be mentally prepared for this possibility and trust your medical team’s expertise.

To Wrap It Up

Handling a high-risk pregnancy can understandably add stress to the journey for both moms and dads. However, being well-informed about what lies ahead can make a world of difference in feeling more prepared!

Remember, if you’re expecting those adorable mono mono twin girls or boys, it’s essential to remember that while complications can be a concern, they don’t necessarily become a reality for everyone. Thanks to the vigilant care provided by your healthcare team, most babies transition into healthy lives outside the womb.

Until the next post, I’m sending you all the positive energy and love your way!

With Gratitude,


I’d love to hear from you! If you have any questions or want to share your experiences, please don’t hesitate to comment below. Your insights and comments are invaluable to us and the wider community. ✨🙏🏼


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About The Author

Linds is the proud mom of two little miracles, Mono Mono twin girls, and one AMAZING older brother! She is the founder and content creator of Mono Mono Twins, Intensive Therapy for Kids, and Co-Founder of The LENN Foundation, a 510c3 that helps children across the United States with cerebral palsy receive grants for intensive therapies to thrive.


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The contents of the Mono Mono Twins Site, such as text, graphics, images, and other material contained on the Mono Mono Twins Site (“Content”), are for informational purposes only. The Content is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition.

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