After your intrauterine insemination (IUI) monitoring appointment, your fertility doctor might inform you of good news, that an ovarian follicle is maturing and will soon release an egg. While this is a positive sign that ovulation is near, you may be wondering whether it is possible to have twins with just one mature follicle.
How do follicles play a role in conceiving twins?
An ovarian follicle is a fluid-filled sac in each ovary that holds an immature egg that’ll grow and develop during your menstrual cycle. In a typical 28-day menstrual cycle, a mature follicle will release the egg inside it around day 14, in a process called ovulation.
The released egg then travels down the fallopian tubes, where it waits to be fertilised by sperm cells. Usually, only one follicle matures completely after each menstrual cycle, releasing one egg, which typically results in a single pregnancy. However, in rare cases, two or more follicles mature simultaneously, making it possible for more than one egg to be released during the same treatment cycle.
Is it possible to conceive twins via IUI with one follicle?
Twin pregnancy after IUI with one mature follicle is uncommon, but it can still happen. Fertilisation after IUI still takes place naturally in the fallopian tube, so a twin pregnancy may occasionally occur even when only one follicle is present.
In some cases, this may result in identical twins, when a single fertilised egg divides into two embryos. If fertility medication or ovarian stimulation is used during an IUI cycle, more than one follicle may develop and release an egg, which can increase the chance of fraternal (dizygotic) twins or multiple pregnancy.
Published figures from some studies suggest that when only one mature follicle is present, the chance of twins is low, at around 1–2%.
If you'd like further information about the possibility of having twins with IUI, schedule a consultation with Thomson Fertility Centre. Our fertility specialists can discuss whether ovarian stimulation is appropriate for your individual circumstances and monitor your follicle development throughout treatment.
What factors are associated with twin pregnancies?
If you and your partner want to have twins, there are a few factors that can affect your chances of getting pregnant with them. These include:
Maternal age:
If you are in your 30s or 40s, you will usually have higher oestrogen levels, which naturally stimulates multiple follicles to mature.
These hormonal changes mean you are more likely to release more than one egg during ovulation, which may result in more than one egg being released during ovulation.
Family history:
A family history of twin pregnancies may be one of the factors linked to a higher chance of twins.
This may be related to hyperovulation, where the body releases more than one egg during ovulation, which can increase the likelihood of fraternal (dizygotic) twins.
Previous twin pregnancies:
Having experienced a twin pregnancy previously may be one of several factors your doctor considers when reviewing your medical history.
Weight and height:
Some studies suggest that body weight and height may be associated with the chance of twin pregnancy.
- Hormonal factors, including insulin-like growth factor, may play a role in this.
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What are the potential risks of having a twin pregnancy?
Before deciding to have a twin pregnancy, you should be aware of some risks that will allow you to make an informed decision about your fertility journey. These risks include:
Side effects of fertility medication
Before your IUI insemination procedure, your fertility doctor may prescribe injectable medications or ovulation induction drugs, such as gonadotropins, to stimulate your ovaries to develop multiple ovarian follicles.
While these medications are generally safe, they can occasionally cause ovarian hyperstimulation syndrome (OHSS), whereby the ovaries respond more strongly than usual and become enlarged. In severe cases, this can lead to complications such as kidney problems, blood clots, and breathing difficulties.
Increased maternal risk
Carrying twins can place additional demands on the body, which may increase the likelihood of certain pregnancy-related complications, such as:
Anaemia, a condition where there aren't enough healthy red blood cells to carry oxygen around the body.
Gestational diabetes is a type of diabetes that develops during pregnancy when the body cannot produce enough insulin to manage increased blood sugar levels.
Gestational hypertension, which is high blood pressure caused by the heart working harder when carrying twins
Placental complications, such as placental abruption, where the placenta separates from the wall of the uterus earlier than expected.
Postpartum haemorrhage, which refers to heavier bleeding after delivery.
A higher likelihood ofcaesarean section.
Increased foetal risk
Twin pregnancies are more likely to deliver earlier than singleton pregnancies, often around 36 to 37 weeks rather than 40 weeks. As a result, twins may have a higher chance of being born prematurely or having a lower birth weight.
For personalised guidance about twin pregnancy possibilities for your fertility condition, schedule a consultation with our fertility specialists at Thomson Fertility Centre.
FAQ
Can follicle size affect the likelihood of having twins?
Follicle size is one of the factors your fertility specialist may consider when assessing the chance of twins or multiple pregnancy during IUI treatment. In general, the presence of two or more mature follicles is considered more relevant than size alone.
If two or more follicles measure around 18 to 24 mm, this may increase the likelihood of twins or multiple pregnancy, as more than one egg may be released during ovulation. However, twin pregnancy is not determined by follicle size alone, and it will still depend on whether more than one egg is fertilised.
Can IUI work with one follicle?
Pregnancy can still occur with IUI when there is one mature follicle. While some treatment plans may involve more than one follicle, having a single mature follicle does not mean IUI cannot be considered.
What matters is whether the follicle matures appropriately and releases an egg at the right time, alongside other factors such as sperm quality, ovulation timing and your overall fertility profile.
Is there a chance of having twins with IUI?
Twin pregnancy can occur with IUI, although the likelihood is generally low. Published figures from some studies suggest that when no fertility medication is used, twin pregnancy may occur in around 1–2% of IUI pregnancies.
If ovarian stimulation is used as part of treatment, the likelihood of twins may be higher, as more than one follicle may develop and release an egg. Some studies have reported twin pregnancy rates of around 5–12% in stimulated IUI cycles, depending on factors such as the number of mature follicles and the treatment protocol used.
Can one follicle produce two eggs?
No, each follicle contains and releases only one egg. This is why having multiple mature follicles increases your chances of having twins: each follicle contributes one egg, so two follicles mean two potential eggs that can be fertilised.
Is the second IUI more successful?
There is no clear evidence that a second IUI cycle is more successful than the first. Treatment outcomes can vary from cycle to cycle and depend on individual factors such as your age, fertility profile, response to medication and follicle development during that cycle.
Do trigger shots increase the chance of twins?
Trigger shots do not directly cause twins. Their main role is to help time ovulation for your IUI cycle. The chance of twins is more closely linked to the number of mature follicles present, particularly if ovarian stimulation has led to more than one follicle developing.
The information provided is for general guidance only and should not be considered as medical advice. For a personalised fertility consultation and tailored advice, schedule a consultation with Thomson Fertility Centre today.
For more information, contact us:
Thomson Fertility
- Paragon: 6252 7766
- Novena: 6399 3758, 8811 0358 (WA)
Thomson Specialists (Women's Health)
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