6.12 Embryo Splitting in Surrogacy: A Rare but Exciting Possibility

Every embryo transfer carries hope. Sometimes, that hope multiplies—literally. Though rare, a single embryo can naturally split, resulting in identical twins. This isn’t something anyone can predict, but when it happens, it brings both excitement and a few extra considerations. At GSHC Surrogacy, we’ve guided many families through this experience, and while twin pregnancies do require closer monitoring, they can still be healthy, joyful journeys.

1. How Often Does an Embryo Split?

Embryo splitting is a natural occurrence, and although it can happen in any pregnancy, it's slightly more common during IVF. In IVF transfers, the chance of a single embryo splitting is estimated at around 1–2%, while in natural conception, it’s closer to 0.4% (Hershlag et al., 1999; Blickstein & Keith, 2003). Certain conditions may make splitting a little more likely—such as transferring a Day 5 blastocyst or using assisted hatching—but even then, it remains rare. Most intended parents and surrogates don’t anticipate it, and when it does happen, it’s usually seen as a unique and meaningful surprise rather than a complication.

2. What Happens When an Embryo Splits?

The outcome depends on how early the embryo splits after fertilization. If the split occurs within the first three days, the twins typically each develop with their own placenta and amniotic sac—known as dichorionic-diamniotic (Di-Di) twins. If the embryo splits between days four and eight, the twins usually share a placenta but have separate sacs—called monochorionic-diamniotic (Mo-Di) twins—which is the most common type of identical twins seen in IVF pregnancies (Hack et al., 2005).

If the embryo splits after day eight, the twins may share both the placenta and the amniotic sac (monochorionic-monoamniotic, or Mo-Mo twins), a rare condition that requires more frequent monitoring due to increased risks. In extremely rare cases—after day 13—the embryo may not fully separate, resulting in conjoined twins. While these situations are uncommon, they highlight the importance of early ultrasounds and close care from a high-risk pregnancy team.

3. Our Experience with Twin Pregnancies at GSHC

At GSHC Surrogacy, we’ve supported many surrogates and intended parents through twin pregnancies. While they require extra care, we’ve seen that—with the right preparation—they often lead to beautiful, healthy outcomes.

Surrogates carrying twins typically have more prenatal appointments and monitoring. We make sure they have access to the medical care and emotional support they need. Nutrition, rest, and pacing physical activity become even more important, and we work closely with the surrogate and her care team to make sure she’s well-supported throughout the process.

Most surrogates are open to carrying twins as long as their medical provider agrees it’s safe. What makes the difference is consistent, honest communication between the surrogate, the intended parents, and our agency throughout the journey.

4. Talking About Twins Before Matching

Because embryo splitting isn’t something we can control, it’s something we plan for from the beginning. At GSHC, we make sure all parties are on the same page about twin pregnancies during the matching process—before contracts are signed or embryos are transferred.

These conversations cover the surrogate’s comfort level with carrying twins, how she feels about reduction in case of medical necessity, and how decisions would be made if twins are confirmed. We believe that these conversations, while sometimes sensitive, are best handled early—with clarity and respect. Every surrogate has the right to set boundaries, and we help ensure those are honored from the very beginning.

5. When Reduction Is Medically Recommended

The vast majority of twin pregnancies at GSHC result in the safe delivery of two healthy babies. But in rare situations, a doctor may recommend selective reduction for medical reasons.

This could happen in cases of twin-to-twin transfusion syndrome (TTTS), where blood flow between the twins becomes unbalanced, or in conditions like TRAP sequence, severe growth restriction of one twin (sIUGR), or monoamniotic twins with umbilical cord complications (Evans et al., 2004; Lewi et al., 2010; Reddy et al., 2005; Moise, 2018).

If reduction is recommended, the decision is never made lightly. Our team supports all parties with compassion and guidance, ensuring that both the surrogate and intended parents have the support and information they need to navigate a very personal and difficult decision.

6. What We’ve Learned from Supporting Twin Pregnancies

Every pregnancy is different. Every surrogacy journey is personal. But time and again, we’ve seen that with thoughtful planning and strong communication, even the unexpected can turn into something extraordinary.

Many of our surrogates who’ve carried twins describe it as one of the most rewarding parts of their journey. Intended parents who learn they’re having twins often experience a mixture of surprise and joy—and with good support, that initial surprise turns into excitement and anticipation.

What matters most is preparation. When expectations are aligned and support is steady, the path forward feels clearer—even when it takes an unexpected turn.

Citations & References

American College of Obstetricians and Gynecologists (ACOG). (2021). Multifetal Pregnancy: Twin, Triplet, and Higher-Order Multifetal Pregnancies.
Blickstein, I., & Keith, L. G. (2003). The Decreasing Incidence of Monozygotic Twinning. Journal of Assisted Reproduction and Genetics, 20(4), 99–102.
Evans, M. I., et al. (2004). Selective Reduction in Multifetal Pregnancies. New England Journal of Medicine, 351(8), 870–875.
Hack, K. E., et al. (2005). Perinatal Outcomes of Monoamniotic Twin Pregnancies. Obstetrics & Gynecology, 106(5), 1081–1087.
Hershlag, A., Paine, T., Kvapil, G., Kvapil, R., & Feng, H. (1999). Monozygotic twinning associated with assisted reproduction: A review. Obstetrical & Gynecological Survey, 54(8), 537–547.
Lewi, L., et al. (2010). Clinical Management of TRAP Sequence. American Journal of Obstetrics & Gynecology, 203(5), 401.e1–401.e7.
Moise, K. J. Jr. (2018). Diagnosis and management of twin-twin transfusion syndrome. Clinical Obstetrics and Gynecology, 61(2), 287–297.
Reddy, U. M., et al. (2005). Monoamniotic twins: A review of the literature. American Journal of Obstetrics and Gynecology, 192(2), 479–489.

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