Fertility drugs and the risk of multiple births

Infertility treatments that cause multiple eggs to develop make it more likely to become pregnant with twins, triplets, or more. This is called multiple gestation. Although some people might think it would be nice to have many babies at once, this may not be good for the health of the pregnant woman or her future children.

How likely is multiple gestation?

The chances of a multiple gestation depend on the type of fertility medication used, the number of follicles produced, and the age of the person in treatment. The risk of multiple gestation can be as low as 3% (1 in 33) during in vitro fertilization with a single embryo transfer, or as much as 8% (1 in 12) with clomiphene citrate or 30% (1 in 3) with gondadotropins to help someone ovulate. With oral or injectable medication, the number of eggs recruited, and the age of the woman are far more important in determining multiple gestation risk than the particular approach to obtaining eggs.

What could happen to the babies?

The babies could be born too early, which is called premature birth. Half of all twins and 90% of all triplets are born prematurely. Babies born prematurely may have many health problems. Their lungs might not be strong enough, so they might have trouble breathing. The blood vessels in their brains might bleed easily. Many other birth defects are associated with multiple births as well. The babies will probably be underweight and may get sick or even die.

Before birth, the babies might not get all the nutrition that is carried by the blood from the placenta (the tissue that carries nutrients from the pregnant person to the baby). This is particularly true if the twins are identical and share a placenta. The babies may not grow as fast as normal. If twins share important blood vessels through a common placenta, they may develop heart problems or die. Twins, triplets, and other multiples are more likely to have problems with their brain development and nerves if they are born early. One of the more common problems is cerebral palsy, an abnormality of the brain. Other problems associated with multiple births may not become known for many years after delivery.

What could happen to the pregnant person?

While many people will ultimately do well with a multiple pregnancy, potential problems could include high blood pressure, diabetes, anemia (low blood count), or too much or too little amniotic fluid (the fluid that surrounds the baby during a pregnancy). Too much amniotic fluid can be a problem because it can cause premature labor, while too little fluid can cause a problem with the baby’s development. Staying in bed or the hospital for weeks before delivery may be recommended, especially with signs of premature labor. Also, the delivery itself may be more complicated. There is a higher likelihood of undergoing a Cesarean section, which is when the babies are delivered through a surgical opening in the belly.

What can I do to reduce the risk of multiple births?

During a fertility treatment cycle when fertility drugs are used with timed intercourse or insemination, your doctor will monitor your cycle very carefully. The use of fertility medications makes it more likely that one or more eggs will be fertilized. However, if it appears that too many eggs are developing, your doctor may cancel your cycle and tell you not to have an insemination or intercourse to reduce or eliminate your risk of multiple births. During in vitro fertilization (IVF), the egg and sperm are joined (fertilized) in the laboratory. The resulting embryo (fertilized egg) is then placed into the womb (uterus). Multiple gestations are least likely when one embryo is placed in the womb. ASRM has published guidelines on the number of embryos to transfer when undergoing an IVF cycle. These guidelines can be found at www.asrm.org.

Some pregnancies may start as a multiple gestation but undergo what’s called a “spontaneous reduction”. This is when one of the pregnancies stops growing (miscarriage) and the other pregnancy continues normally. No treatment is needed when this occurs, and ultrasounds can determine if the remaining pregnancy is growing normally. In some cases, the risk of a multiple gestation is too great. A doctor may suggest that you consider a procedure called selective reduction. Selective reduction is a procedure to reduce the number of fetuses to one or two. Usually, the procedure is done after the risk of a miscarriage, but still early in the pregnancy to increase the chance of a healthy and successful pregnancy. Choosing to do this procedure is difficult. Individuals and couples who are thinking about this option should talk to their doctor and a counselor.