Types of Fibroids

Do Fibroids Affect Pregnancy?

Most women with fibroids have no more trouble becoming pregnant than women who do not have fibroids, and their risk of a bad pregnancy outcome is no higher.

About 1 in every 15 women with infertility has fibroids, but the fibroids are usually innocent bystanders: They cause only 2% to 3% of cases of infertility. Fibroids that block one or both of the fallopian tubes may prevent sperm from fertilizing an egg. Fibroids that fill the uterine cavity may block implantation of a newly fertilized egg.

Fibroids-especially those located in the cavity of the uterus-may increase the chance of a miscarriage or may cause a woman to go into labor before her due date (premature labor). Fibroids may also increase the chance that the baby is not positioned to come out headfirst. This can increase the need for cesarean section. Rarely, fibroids can cause complications of pregnancy called placental abruption and postpartum hemorrhage

What Is Placental Abruption?

After childbirth, the afterbirth (placenta) separates from the uterus. Placental abruption occurs when the placenta separates from the uterus too quickly (i.e., before the baby is born). It occurs in one of every 200 pregnancies. In addition to causing vaginal bleeding and pain, placental abruption can cut off the baby's supply of nutrients and blood. In severe cases, this can threaten the baby's life.

What Is Postpartum Hemorrhage?

Normally, the afterbirth (placenta) separates from the uterus after childbirth. When this happens, the muscle in the uterus usually squeezes the uterus to help stop bleeding. If a fibroid is present, the squeezing of the muscle in the uterus may be less effective and the woman may have more bleeding. Rarely, the blood loss may be significant and the woman may need medications, surgery, and/or a blood transfusion. Some fibroids grow during pregnancy, but some remain the same size and others shrink.

Fibroids, Fertility and Pregnancy

Can Fibroids Cause Fertility Problems?

Fibroids that change the shape of the uterine cavity (submucous) or are within the cavity (intracavitary) decrease fertility by about 70% and removal of these fibroids increases fertility by 70%. Other types of fibroids, those that are within the wall (intramural) but do not change the shape of the cavity, or those that bulge outside the wall (subserosal) do not decrease fertility, and removal of these types of fibroids does not increase fertility. (see: Hysteroscopic Myomectomy) Regular ultrasound is not the best way to determine exactly where fibroids are. For this information, MRI is best, but most expensive. Hysteroscopy (looking in the cavity with a small telescope) and saline-infusion sonography (ultrasound after sterile water is placed into the uterine cavity) are also very good.

Can Fibroids Cause Miscarriage?

Fibroids that bulge into the uterine cavity (submucous) or are within the cavity (intracavitary) may sometimes cause miscarriages. The fertilized egg comes down the fallopian tube and takes hold in the lining of the uterus. If a submucosal fibroid happens to be nearby, it can thin out the lining and decreases the blood supply to the developing embryo. The fibroid may also cause some inflammation in the lining directly above it. The fetus cannot develop properly, and miscarriage may result. However, with the next pregnancy, it is possible that the egg will settle in another location, and pregnancy may proceed without problems. However, if you do have a miscarriage and a fibroid is found bulging into the uterine cavity, it is advisable to have it removed. (see: Hysteroscopic Myomectomy)

I am including the following journal abstract regarding fibroids and fertility:

Fibroids and infertility: a systematic review of the evidence.
Author: Pritts EA. Obstet Gynecol Surv. 2001 Aug;56(8):483-91.

A systematic literature review was performed to determine whether leiomyomata are associated with decreased fertility rates, and whether surgical removal increases fertility rates postoperatively. Meta-analysis was conducted when multiple studies addressed a single issue and were sufficiently homogeneous. Data were analyzed for effect of any fibroid upon fertility, as well as specific fibroid location.

Results of studies comparing women with infertility and fibroids versus infertile controls showed widely disparate results. Subgroup analysis failed to indicate any effect on fertility of fibroids that did not have a submucous component. Conversely, women with submucous myomas demonstrated lower pregnancy rates (RR 0.30; 95% confidence interval [CI] 0.13--0.70) and implantation rates (RR 0.28; 95% CI 0.10--0.72) than infertile controls. Results of surgical intervention were similar. When all fibroid locations were considered together, myomectomy results were again widely disparate.

However, when women with submucous myomas were considered separately, pregnancy was increased after myomectomy compared with infertile controls (RR 1.72; 95% CI 1.13--2.58) and delivery rates were now equivalent to infertile women without fibroids (RR 0.98; 95% CI 0.45--2.41). The current data suggest that only those fibroids with a submucosal or an intracavitary component are associated with decreased reproductive outcomes, and that hysteroscopic myomectomy may be of benefit.

Does Pregnancy Make Fibroids Grow?

Pregnancy has an unpredictable effect on fibroids, but most fibroids do not increase in size during pregnancy. The effect of pregnancy on fibroid growth probably depends on individual differences in the genetic changes in each fibroid and the type and amount of growth factors that are present in the blood. An ultrasound study of pregnant women with fibroids found that 69% of the women had no increase in the size of fibroids throughout the pregnancy. In the 31% of women who had an increase in size, it usually happened before the third month. Almost always, fibroids shrink after delivery.

Can Fibroids Cause Problems During Pregnancy?

Although many women will have fibroids during their lifetime, the fibroids most often occur in women in their late thirties and forties, a time in life many women have already completed their families. Only 2% of pregnant women are found to have fibroids when examined with ultrasound. Also, the vast majority of women who are pregnant and do have fibroids encounter no problems. They go on to have full-term, healthy babies without difficulty. Most studies show no differences in the risk of premature delivery, fetal growth problems, fetal abnormalities, placental problems, or heavy bleeding after delivery. The need for caesarean section, however, is more common among women who have fibroids (see below).

During pregnancy, the placenta makes large amounts of female hormones which may rarely cause fibroids already present to grow. Very rarely, if the fibroids grow too quickly the blood vessels supplying them may not be able to get enough oxygen to the tissue and degeneration of the fibroid cells can then occur. This process of degeneration can cause pain, but usually resolves in a short time without treatment and without harm to the baby. Some women may have mild contractions during this time, but it is extremely rare for premature labor to actually begin. However, it is crucial that a pregnant woman with fibroids see her physician if she experiences pain or contractions. Bed rest, heat, and pain medication will usually be prescribed, and medications to inhibit premature labor may sometimes be needed.

Can Fibroids Hurt the Developing Baby?

Fibroids almost never cause injury to a baby. Review of the entire world's medical literature for the past 25 years discovered only four babies affected by a fibroid.

Do Fibroids Mean You Need a Caesarean Section?

Rarely, a fibroid may grow near the cervix during pregnancy. If it is large enough, it may prevent the baby from coming through the birth canal. This is not dangerous and can often be diagnosed by a sonogram before labor begins. Sometimes this problem is discovered during labor because the baby does not come down the birth canal. A caesarean section is then performed. However, most women with fibroids deliver their babies without any problems.

Can fibroids cause fertility problems?

There is evidence that fibroids are associated with subfertility (reduced fertility). They have been linked with an increased risk of miscarriage in the first and second trimester and an increased risk of premature delivery. Fibroids have also been linked with a reduction in the success rate of fertility treatments. However, there is lack of agreement on exactly how and why this is so, because some women go on to conceive and have successful pregnancies despite having relatively large fibroids. One theory is that the fibroids distort the uterus in a way that affects conception, while another theory is that the ability to carry a pregnancy is impaired because the fibroid affects the blood flow.

If you know you have a fibroid and you're having problems conceiving then see your doctor for referral to a fertility specialist. The first course of action will be to find out whether there are any other possible causes of the fertility problem and treat them, if necessary.

Fibroids alone probably only cause fertility problems in less than 3 per cent of women. If this applies to you then your doctor may advise you to continue to try to conceive naturally for up to two years, unless you are over 34 years of age. In this case you are better off seeking treatment sooner rather than later, because fertility tends to rapidly decline with age.

It is unlikely that you will be offered IVF straight away, as there is little evidence that this improves your chances of a successful pregnancy. There is also a lack of evidence on whether surgery helps women with fibroids to conceive and go on to have a successful pregnancy. Your specialist will work with you to decide on the best treatment option for your case.

Fibroids and pregnancy

Most fibroids do not get in the way of a pregnancy. They may cause discomfort, but they generally do not cause any other problems. Some fibroids in certain areas, however, can make conception difficult or lead to miscarriage. Fibroids may press against, or block the entrance to, the fallopian tubes, thus preventing the egg from reaching the uterus. Submucous fibroids that grow inwards into the womb are thought to cause recurrent miscarriage.

A fibroid can also interfere with labour and birth if it blocks the passage to the birth canal. If this is the case, your doctor may recommend a Caesarean section. Fibroids may increase your risk of bleeding heavily after birth, and can increase the time it takes for your womb to return to its normal size.

Just as fibroids can affect pregnancy, pregnancy can affect fibroids. It is thought that fibroids grow during pregnancy because of higher levels of oestrogen, but there is little evidence to support this. Another effect of pregnancy on fibroids is something called 'red degeneration.' This is when a fibroid’s blood supply is cut off, causing it to turn red and die. It can also happen outside of pregnancy but it usually occurs in the middle weeks of a pregnancy. Red degeneration can cause intense abdominal pains and contractions of the womb, which could lead to early labour or miscarriage. If you feel these symptoms, tell your doctor. The pain and contractions usually stop on their own but your doctor may give you drugs to ease the pain and stop the contractions more quickly.

Fibroids are never removed during a pregnancy because of the risk of haemorrhage (bleeding).