Fibroids and Pregnancy

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Fibroids and Pregnancy - All you need to know

The potential effects of fibroids on pregnancy and the potential effects of pregnancy on fibroids are a frequent clinical concern since these benign tumors are common in women of reproductive age.

Fibroids can be the cause of infertility and/or increase the risk of complications during pregnancy. This varies considerably depending on the size and number of fibroids as well as the position of the fibroids in relation to the uterine wall.

Most women will fall pregnant never knowing they had fibroids in the first place. In others, there might be a slight increase in obstetrics complications such as miscarriage, preterm labour, pain during pregnancy, fetal malpresentation and Caesarean section deliveries.

How fibroids affect pregnancy

Most women with fibroids are able to fall pregnant and deliver healthy babies.  

In some cases, however, fibroids can cause significant complications. These tend to be more significant the larger the size and the number of fibroids.

Pregnancy complications associated with fibroids include:

Pregnancy complications associated with fibroids include:

• Pain: uterine fibroids are normally asymptomatic during pregnancy. In symptomatic women, pain is the most common symptom and can be associated with admission to hospital. The frequency of pain increases with increasing size and is especially high in women with large fibroids.

• Increased chance of miscarriage:  Some types of fibroids can be associated with increased rates of miscarriages as they can affect implantation, placentation and uteroplacental circulation.

• Restriction of fetal growth: Fibroids can grow and take up a lot of room in the womb as well as the blood supply. It is possible that large fibroids may be associated with infants that are small for gestational age.

• Fibroid degeneration: Some fibroids can grow fairly quickly. They need an increase in blood vessels (arteries and veins) to support this growth. When the supply of vessels does not follow the fast growth of fibroid, parts of it may degenerate or necrose. This can be quite an acute event and accompanied by severe pain that can last several days.

• Preterm labour and delivery: There is an increased risk of preterm labour and delivery in women with fibroids. Multiple theories have been proposed to explain earlier labour in the setting of fibroids. It is possible that it is related to uterine distension, unbalance of enzymes and/or induction of contractions by the fibroid.

• Malpresentation: This is defined as the baby being in other positions other than head first. The most common ones are breech (when the pelvis or legs are low) and transverse (when the bay is sideways with the head to one side and the pelvis to the other). This is caused by changes in the shape of the uterus caused by the fibroids. It may result in difficult or not possible labour requiring a caesarean section.

• Caesarean section delivery: women who have fibroids are more likely to require a caesarean than those who do not have them. This is caused by many factors including malpresentation, dysfunctional labour, obstruction of the birth canal, and fetal heart rate abnormalities related to placental abruption. Caesarean section can also be the recommended mode of delivery in women who had a myomectomy.

• Antepartum bleeding and abruption of the placenta: abruption is an early separation of the placenta from its connection to the uterine wall. Some studies have shown the risk of abruption is increased threefold in women with fibroid. This can be caused by abnormal blood supply of the placental site, leading to placental ischaemia and necrosis.

Can I get pregnant if I have fibroids?

Yes. Many women with fibroids do get pregnant and have successful deliveries. Some only find out they have fibroids during their pregnancy.

If fibroids are thought to be the case of infertility, an operation to remove them called myomectomy may be necessary.

How do Fibroids affect fertility?

Although fibroids can affect fertility, a lot of women have no trouble getting pregnant with fibroids. In fact, for most, conceiving naturally is possible and usually does not require treatment.

However, there are some cases when getting pregnant with uterine fibroids is difficult.

The ways in which fibroids can cause infertility include:

Mechanical/anatomical factors 

• Fibroids can grow towards the cervix diminishing or blocking the entry of sperms into the uterus

• They can grow towards the fallopian tubes, impairing or blocking the passage of the egg.

• Submucosal fibroids that grow inside the uterine cavity can work as a foreign body and reduce the space for implantation of the embryo and development of the fetus.

Functional/physiological factors

• Fibroids can change the endometrial receptivity to embryo implantation by changing the hormonal milieu, blood flow and hence endometrial development. This was shown in studies using assisted reproductive fertility where the removal of fibroids increased the success rate after IVF treatment.

There are many causes of infertility and they are not always obvious. Infertility patients may have to undergo other investigations to rule out other factors before attributing their difficulty to fall pregnant to fibroids.

Is it safe to get pregnant with fibroids?

Fibroids during pregnancy are not necessarily a major concern. In fact, a lot of women with fibroids get pregnant and deliver a healthy baby. There are also some women who only find out they have fibroids during their routine pregnancy check-ups.

Still, fibroids and pregnancy complications can and do happen together. As such, a doctor would still closely monitor a patient with fibroids to ensure there are no signs of problems.

Can Fibroids be treated during pregnancy?

Fibroid removal during pregnancy may be recommended by a doctor for very specific reasons.

However, fibroid surgery during pregnancy is quite risky for the mother and the baby and only becomes an option when the complications of non-removal outweigh the risk of surgery. In general, the safest option is to wait till after a successful childbirth before removing the fibroid(s).

Is it harder to get pregnant with fibroids?

Having fibroids does not necessarily eliminate a woman’s chance of getting pregnant. Many women have, in fact, fallen pregnant and delivered healthy babies even with fibroids.

As explained in the main text, depending on the location and size of the fibroids, some can interfere with transport and retrieval of sperm and egg due to anatomical distortion of cervix, uterine cavity, tubal ostia and ovary. They can also interfere with fertilisation and/or the successful implantation of the embryo.

Do fibroids grow in size during pregnancy?

It is common for fibroids to grow as the pregnant uterus grows. Size of fibroids may be affected by change in estrogen and progesterone levels, uterine blood flow, and, possibly, human chorionic gonadotropin levels. This however does not happen in every case. In some women, fibroids stay stable at a very similar size throughout the pregnancy and others even experience reduction in size of the fibroid(s).

Do fibroids shrink after a pregnancy?

Fibroids do tend to shrink in the months after delivery. The whole uterus reduces in size, there are changes in blood flow and hormone patterns.

Studies have shown that majority of women(up to 90%) with fibroids detected in first trimester will have regression in total fibroid volume three to six months post-partum.

What treatments are available for women who have fibroids and are wanting to fall pregnant?

Each case should be assessed individually in its own merits taking into account the situation of each woman.

It is important to make the distinction between

• women who are having treatment because they are trying to fall pregnant and the fibroid(s) seem to be causing infertility or miscarriages.

• women who need treatment for symptomatic fibroids and want to preserve fertility but are not or have not yet tried to conceive.

As a general guide, the table below summarizes the available options: