What Are Twiblings vs. Surrogate Twins?

There are so many reasons why a future parent may want to have twins. Two children at the same time are just so incredibly adorable. If one is cute, isn’t two just double the cuteness? For some couples or individuals, this dream might be something they have to achieve through a gestational carrier or surrogate. However, understanding the process in its' entirety and all your options first can help ensure you're making the best decision for everyone involved.

Considering Surrogate Twins

Many patients who visit me in their later years believe that it’s more manageable to handle the physical demands of two infants at once, as opposed to dealing with them one after the other. Some find that using a gestational carrier to carry two babies at the same time can also be more affordable, as they wouldn't have to search for another carrier in the future.

Risks of Carrying Surrogate Twins

There are many perinatal complications that are increased with twins over singletons including fetal anomalies, preeclampsia, and gestational diabetes. One of the most consequential complications found with twins over singletons is pre-term birth and the associated infant morbidity and mortality. 

Below are some statistics published in a recent ACOG bulletin: 

• The mean birth weight of twins when compared to singletons is significantly less, the mean gestational age for twins is 35 weeks while it is 38.5 weeks for a singleton. 
• The percentage of twins born earlier than 34 weeks is 19.5 % while the percentage of singletons born prior to 34 weeks is 2.1 %. 
• The percentage of twins born earlier than 37 weeks is 60% while the percentage of singletons born earlier than 37 weeks is 8.2%. 
• The rate of cerebral palsy for twins is 7 out of 1,000 live births while the rate of cerebral palsy in singletons is 1.6 out of 1,000 live births. 

Here’s the big one: Infant mortality is 23.6 out of 1000 live births for twins compared to 5.4 out of 1,000 for singletons. 

Twins have a significantly higher risk to the baby when compared to singletons in relation to birth weight, gestational age, prematurity, severe prematurity, cerebral palsy, and infant mortality. This is aside from all of the other complications like fetal anomalies, preeclampsia, gestational diabetes post-partum hemorrhage, and NICU admissions. Bottom line is that twins are just so much riskier for both the gestational carrier and the baby when compared to singletons. 

Freezing Embryos

If you are going to create embryos via in vitro fertilization (IVF) and you would like to have more than one child, there is no need to put two embryos into a gestational carrier’s uterus in the hopes of having twins. This carries too many risks. 

My advice to intended parents is to create the embryos that they need for their current and future pregnancies. Keep them frozen until they are ready to use them since the amount of time the embryos are frozen will not affect the chance of a resulting pregnancy. The length of time an embryo is frozen does not have an effect on the success of an embryo transfer or pregnancy. We know that the chance of pregnancy after the embryo transfer of a euploid (chromosomally normal) embryo is about 60-70% and that stays the same regardless of how long the embryos are frozen. 

What Are Twiblings? 

If you are using a gestational carrier and you just want to have two children at the same time, there are alternative options besides having surrogate twins.

Instead of twins, consider having twiblings, two infants who are twin-like but are actually siblings. We can accomplish this by transferring two embryos (created from the same egg and sperm source and so in essence are siblings) into separate gestational carriers at about the same time. 

This will increase the chance of having two babies born around the same time from two different gestational carriers. This provides all the benefits of having twins (tackling two kids all at once, double the cuteness, etc.) without the risk of having one person carry both fetuses at the same time.