If you and your husband are considering artificial insemination to conceive twins and are wondering what are the chances of twins with IUI. It is important to first clarify what intrauterine insemination (IUI) means. IUI is a procedure in which a sample of your husband’s sperm is prepared and then placed directly into the uterus around the time of ovulation. But does IUI actually make twins more likely? And what factors affect that rate? We explain below.(1)
Chances of Twins With IUI: Does It Increase the Odds?
Intrauterine insemination (IUI) itself does not directly increase the likelihood of a twin pregnancy. However, the chance of twins is increased by ovulation-inducing medications (such as Clomid), which are often used during an IUI cycle. Ovulation induction medications can cause more than one mature follicle to develop and more than one egg to be released at ovulation, rather than a single egg. This creates the opportunity for two or more eggs to be fertilized in the same cycle, resulting in fraternal (non-identical) twins. (1)
Chances of Twins With IUI: Rates
The chance of having twins after intrauterine insemination (IUI) varies from one woman to another and depends on several factors. These include the woman’s age, the type and dose of fertility medications used, how the ovaries respond to stimulation, and the number of mature follicles present before the procedure. To give a general idea, data from the Spanish Fertility Society for 2023 showed that around 8% of deliveries resulting from IUI using the partner’s sperm were twin births. (2)
It is important to note that this figure refers to the proportion of twin births among pregnancies that resulted in a live birth after treatment, not the chance of having twins with every IUI attempt.(3)
The higher chance of twins is mainly linked to ovarian stimulation. When more than one mature follicle develops, more than one egg may be released. If two eggs are fertilized, this can result in a fraternal twin pregnancy. (3)
Factors that Increase the Chances of Twin Pregnancy
Some of the most important factors increasing the risk of twin pregnancies include:(2)
- Use of ovarian stimulation medications: This is a main factor in increasing twin pregnancy risk.
- Advanced maternal age: Women in their 30-40s are more likely to conceive twins than younger women.
- A higher number of previous births: The chance of having twins tends to increase with the number of previous pregnancies.
- A family history of fraternal twins in the woman’s family: Genetics can also play a role, particularly when there is a history of twins on the mother’s side of the family.
What are the Risks of Twin Pregnancy?
Twin pregnancies carry a higher risk of complications for both the mother and the babies. Such as: preeclampsia, gestational diabetes, and preterm birth.
There is also a chance of one or both babies growing slower than expected,causing a difference in their growth rate and low birth weight.
Many of the complications seen in twin pregnancies are related to preterm birth. Thus twin pregnancies usually require more frequent medical monitoring to keep track of both the mother’s health and the baby’s growth and development.
Some of the key statistics related to twin pregnancies are: (2)
|
Twin pregnancy |
Singleton Pregnancy | Potential Complication |
| 10-12% | 6% | Preeclampsia |
| 5-8% | 3% | Gestational diabetes |
| 50% | 10% | Preterm birth (before 37 weeks) |
| 53.2% | 6.2% | Birth weight below 2.5 kg |
| 10.5% | 1.2% |
Birth weight below 1.5 kg |
These are general estimates not figures specific to IUI pregnancies or individual predictions.
