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 if one follicle will allow you to conceive the twins you are hoping for.
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, increasing the chances of conceiving twins.
Is it possible to conceive twins via IUI with one follicle?
Since IUI only shortens the distance that the sperm has to travel to reach the egg in the fallopian tube, the fertilisation itself happens naturally. Therefore, just as with natural conception, it's possible to conceive twins after performing this fertility treatment with only one follicle, although the likelihood is very small at around 1-2%.
Twins from a single egg, or identical twins, can occur when the single egg is fertilised and divides into two embryos. Depending on when the egg cell divides, the embryos can implant themselves in the uterus either together or independently.
However, during the IUI cycle, it is possible that you may be given fertility medication or undergo ovarian stimulation to promote the growth of multiple ovarian follicles. This increased follicle count can result in multiple eggs being released, increasing the likelihood that more than one egg will be fertilised and leading to fraternal (dizygotic) twins.
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 assess whether ovarian stimulation is suitable for you and help monitor follicle growth.
What factors affect the likelihood of conceiving twins?
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 increases the likelihood of conceiving twins.
Family history:
If there is a history of twin pregnancies in your family, you are more likely to have twins.
This can be caused by hyperovulation, where your body releases two or more eggs during ovulation, increasing the likelihood of having fraternal twins.
Previous twin pregnancies:
Having experienced a twin pregnancy previously increases your likelihood of conceiving twins again in future pregnancies.
Weight and height:
Women who are overweight or obese may have a higher chance of conceiving twins naturally due to weight-related hormonal influences.
Additionally, taller women are more likely to have twins, possibly due to higher levels of insulin-like growth factor.
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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
Since there are two babies in twin pregnancies, this naturally places additional demands on the mother's body that can lead to:
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 abruptio placentae, a condition in which the placenta prematurely separates from the uterine wall.
Postpartum haemorrhage, which is heavier bleeding after delivery
An increased risk of caesarean section
Increased foetal risk
Twins typically arrive earlier than single babies, usually around 36 to 37 weeks rather than 40 weeks. This means your little ones may experience a premature birth, which can result in 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?
Although follicle size plays an important role in twin conception, it is more important to have multiple mature follicles than to focus solely on size. If you have two or more follicles measuring 18-24 mm (the ideal size for healthy eggs), your chances of conceiving twins naturally increase, as each mature follicle can release an egg.
However, even with perfectly sized follicles, having twins isn't guaranteed; it depends on the successful fertilisation of multiple eggs.
Can IUI work with one follicle?
Yes, IUI can be successful with just one mature follicle. Although having multiple follicles improves your overall chances of becoming pregnant by providing more opportunities for fertilisation, many couples successfully conceive with only one follicle.
The important thing is to ensure the follicle matures and releases a healthy egg, which is then fertilised by sperm cells at the right time.
Is there a chance of having twins with IUI?
Yes, though the likelihood is relatively low. Twin conception occurs in around 1-2% of IUI pregnancies when no fertility medications are used.
However, if your treatment includes ovarian stimulation to increase the follicle count, your chances of having twins can increase to around 5-12%, depending on how many of the follicles mature.
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 medical evidence to suggest that second IUI cycles are more successful than first attempts.
Whether or not you are likely to succeed on this fertility treatment depends on your individual circumstances, such as your age, specific fertility factors, how well you respond to any medications, and the quality of your follicle development in each cycle.
Do trigger shots increase the chance of twins?
Trigger shots themselves don't directly increase the likelihood of conceiving twins, but they do ensure that your mature follicles release their eggs at the optimal time for your IUI procedure.
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 Centre
- Paragon: 6252 7766
Thomson Specialists (Women's Health)
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