When utilizing any kind of fertility treatment with the goal of getting pregnant, there’s always the chance of successfully conceiving… and sometimes, conceiving more than one baby. If it seems like many women who use In Vitro Fertilization (IVF) to get pregnant end up as the parent of twins (or more babies), that’s because IVF does, in fact, increase your chances of multiples. According to the American College of Obstetricians and Gynecologists (ACOG), research shows that “fertility treatments have contributed significantly to the increase in multifetal pregnancies.”
If you’re considering using IVF to conceive, but are wondering or worried about the possibility of winding up with twins, know that your doctor should explain your unique chances based on your selected treatment. When it comes to having twins through In Vitro or any other assisted reproductive medicine, there’s a lot to know and consider.
What are the chances of having twins through IVF?
Today there are more twins conceived and born than at any other time, according to research by the Centers for Disease Control and Prevention (CDC). Since the 1980s, the rate of twin births rose by nearly 80 percent, and the number of twins born to women between ages 35 and 39 doubled. The twin birth rate reached an all-time record high in 2014 of 33.9 twins born for every 1,000 births. CDC research shows that in the three decades since 1980, almost a million sets of twins were born in the United States.
While these statistics aren’t broken down by naturally conceived twins and those conceived with the help of IVF or assisted reproductive technology (ART), research from 2013 shows that nearly 40 percent of pregnancies that relied on IVF resulted in multiple births. Compared to the natural occurrence rate for multiples of 2 percent of the population, the chances of conceiving twins (or more babies in one pregnancy) through IVF are relatively high.
While this number has drastically increased due to the use of IVF and other fertility treatments, many reproductive specialists and fertility clinics are using newer technology and methods to help reduce the risks of multiple babies in one pregnancy.
Why are the chances of having twins through IVF so high?
To understand why the possibility of having twins or multiples with IVF is so high, you have to consider how IVF works, and techniques that are used to help increase the chances of a successful pregnancy. During the IVF process, several embryos are prepared for possible implantation in the uterus. For decades, fertility doctors have performed the transfer procedure using several embryos at one time, with the hopes that one out of several will implant and lead to a successful pregnancy. In some IVF cases, the transfer fails, and none of the embryos implant (what is considered a “failed” IVF cycle). Yet, in other transfers, multiple embryos may successfully implant instead of just one, leading to the possibility of twins or multiples.
You may be wondering whether it’s necessary to implant multiple embryos if that increases the chances of twins. In years past, limited screening technology made it more difficult for doctors to determine the quality of embryos before they were transferred. For this reason, it made sense to transfer multiple embryos — essentially several chances for pregnancy in one round — to increase the odds of becoming pregnant.
And, there’s a case for implanting multiple embryos for higher chances of success in situations where a woman or couple only has one shot at trying IVF. The cost of fertility treatment is a large factor in how many rounds a person may consider undergoing, and with limited options, some women choose to implant multiple embryos with the hopes that they can have a successful IVF cycle.
Luckily, newer IVF technology makes it easier for fertility specialists and clinics to screen embryos and determine their quality and potential viability. Techniques like allowing embryos to mature a bit longer before implantation can also lead to a more successful implantation. For this reason, many fertility clinics and specialists are reconsidering whether or not they choose to implant multiple embryos at one time. In fact, recent guidelines by the American Society of Reproductive Medicine (ASRM) suggest that transferring multiple embryos at one time may not be the best course of action in many IVF cases. According to ASRM:
“Women with reasonable medical odds of success, those under 35 should be offered single embryo transfer and no more than two at a time,” and for women between the ages of 35 and 40, three embryos at one time should be the maximum number used.
What if I want to conceive twins using IVF?
Some women consider the idea of multiple babies at one time for a variety of reasons, including older maternal age and limited funds that could be put towards IVF in the future. If you are specifically looking to conceive twins, it’s important to discuss this with your fertility doctor. Your provider will be able to counsel you on the pros and cons of twins and multiples, including the benefits and risks. Your fertility doctor will be able to determine your unique chances of having twins. Some common factors that play into the possibility of conceiving twins include:
- Your family health history — Do twins run in your family? If so, your chances of becoming pregnant with twins or multiples may be higher.
- Your body type — Surprisingly, your body type and health may play a role in having twins. Research shows that taller and overweight women are more likely to conceive fraternal twins.
- Your age — Studies show that women over 30, and especially those closer to 40, are more likely to have twins.
- Previous pregnancies — Women who have previously been pregnant are more likely to conceive with the help of IVF, and have higher chances of becoming pregnant with twins or multiples.
Are there risks with conceiving twins through IVF?
While pregnancy is safer now than it has ever been for women, all pregnancies carry some health risks for both mother and baby. Unfortunately, that risk increases in any situation where more than one baby is in the womb.
According to the American College of Obstetricians and Gynecologists (ACOG), pregnancies with multiple babies do have a higher risk of complications for both the mother and babies. Children born in sets (such as twins, triplets, and more) are at a higher risk for a variety of health complications, such as:
- Low birthweight — More than 50 percent of twins are born weighing less than 5 ½ pounds, which increases the risk of other health complications.
- Premature birth — Because there is more strain on the mother’s body when carrying multiple babies, the risk for premature birth caused by early onset labor or other health conditions increases. In fact, nearly 60 percent of twins are born before their due dates. According to the Centers for Disease Control and Prevention (CDC), 37 percent of babies conceived through IVF who are multiples are born prematurely. That rate is just over three times higher than the risk of premature birth for twins conceived without the use of IVF.
- Life-long health concerns — The ACOG reports that twins and multiples have a higher chance of health issues such as learning disabilities and behavioral issues.
- Twin-Twin Transfusion Syndrome (TTTS) — While only occurring in 5 to 10 percent of pregnancies, TTTS is a risk of carrying twins. Twin-Twin Transfusion Syndrome occurs when identical twins share a placenta. With this condition, one baby often receives more blood than the second, creating potentially life-threatening health concerns.
- Intrauterine Growth Restriction (IUGR) — This condition can occur in twin pregnancies, and occurs when one or both babies is not growing at the rate they should. This slow or delayed growth can lead to a variety of health complications for one or both babies.
In addition, the ACOG reports that compared to single pregnancies (ones with just one baby), the risk of stillbirth is higher. For women carrying multiple babies in one pregnancy, the chances of having hypertension (also known as high blood pressure), gestational diabetes, preeclampsia, and postpartum hemorrhage are higher.
Although the risks of carrying multiple babies exist, and sound frightening, many women successfully conceive and carry twins and multiples, and have successful births — both with and without the use of assisted reproductive medicine. When it comes to determining your individual health risks associated with twins or multiples, your fertility specialist will be able to guide you based on your personal health history and fertility situation.
What is multifetal pregnancy reduction?
In some IVF situations, multiple embryos will implant in the uterus, leading to pregnancies with multiple babies. For some families, carrying multiple babies at one time isn’t an option due to health concerns for the babies or mother. In these cases, your doctor or reproductive specialist will discuss the possibility of terminating one or more of the embryos that have implanted during the first trimester.
There are many ethical questions associated with multifetal pregnancy reduction (also called selective termination) and in most cases it is not an easy procedure to consider, especially for women and couples who have struggled with becoming pregnant. Still, the procedure can help with the chances of carrying a baby to term, and at ensuring the health of the mother and baby.