Which Fertility Drug Causes Twins?

There are several factors that influence a woman’s chances of conceiving twins. One of these is the use of fertility drugs or assisted reproductive technology. However, many women conceive twins without any of these factors. Regardless of the reasons, it’s crucial to know the facts and the possible risks involved in the process. Answers are provided by medical experts and should not be construed as medical advice.


Women who take clomiphene may increase their chance of having twins. The drug increases the likelihood of multiple pregnancies and also increases the risk of ovaries becoming enlarged. This condition is known as ovarian hyperstimulation syndrome. The drug can also cause breast tenderness, hot flashes, and mood swings. However, these side effects are rare and will go away when treatment is stopped.

The most common type of twins that occur from clomiphene treatment are fraternal twins, but it is possible to have identical twins as well. Ultrasound scans can help identify the type of twins that are resulting from the drug. Some women may develop monochorionic twins, or twins that share the amniotic sac and placenta.


One of the most common complications of gonadotropin treatment is multiple gestation. This occurs when the ovaries produce multiple eggs, leading to multiple pregnancies. Multiple pregnancies have an increased risk for the mother and for the child. The risk is minimized by carefully monitoring treatment cycles. In some cases, doctors will cancel treatment cycles if more than three follicles develop during a cycle or if the levels of estradiol are too high. This method of reducing multiple pregnancy rates has been successful in lowering the rate to less than 5%. The use of low doses of gonadotropins and a gradual increase in dosage have also been shown to reduce the risk of multiple pregnancy.

Another cause of multiple pregnancies is the use of fertility medications. Injectable fertility medications increase the number of eggs released from the ovaries. When more eggs are released, they can fertilize at the same time, resulting in twins. Fertility medications such as clomiphene and gonadotropins may increase the risk of twins by as much as 30%.


Taking a fertility drug during an IUI cycle can increase the risk of having twins. During this procedure, drugs like letrozole or Clomiphene citrate are used to stimulate ovulation. These drugs increase the number of eggs a woman ovulates and increase the chances of a successful pregnancy. However, these drugs can also cause multiple gestations and twins.

The most common type of twins born after an IUI is fraternal, but sometimes identical twins can occur as well. Early ultrasounds can determine which type of twins are present. Monochorionic twins have identical bodies but share a single amniotic sac and placenta. Monochorionic twins are rare, occurring in less than 1% of twin pregnancies.


There is a significant increase in the number of twins born after IVF. The proportion has increased from 10 percent to 17 percent since 1998. However, not all women who undergo IVF can conceive twins. Doctors often use more than one embryo transfer to increase the chances of conceiving twins.

The risk of having identical twins after IVF is much greater than after natural conception. However, there is still a chance that a single transferred embryo will result in identical twins. These babies are called monozygotic twins. While Dr. Brahma’s suggestion is to put back only one embryo, some women may still experience identical twins.