Will finding uterine fibroids during pregnancy lead to miscarriage? [Doctor-supervised]

What are uterine fibroids?

Uterine fibroids are benign tumors that develop in the uterus, and it is said that one in four women has uterine fibroids in recent years. 

Because it is a benign tumor and not a malignant tumor (cancer), there is no need for emergency treatment, but as fibroids grow larger they can cause severe menstrual pain, anemia, and sometimes infertility, so it is necessary to monitor the condition and undergo treatment if necessary. 

It is a tumor originating from muscle tissue that develops in the uterus and is seen in women in their teens through to their fifties. 

Uterine fibroids grow due to the female hormone estrogen, and shrink after menopause. When fibroids are small, they often have no symptoms, and are often discovered by chance during cancer screening or pregnancy. 

On the other hand, if uterine fibroids become large, the abdomen may become like that of a pregnant woman, and when you touch the abdomen you may feel a hard, lumpy mass, and may experience a variety of other symptoms.

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If uterine fibroids are found during pregnancy, can the pregnancy continue?

As mentioned above, there are many cases where uterine fibroids are found when a woman visits a doctor during pregnancy. Or, they may be found when a woman visits a doctor for infertility consultation. 

Uterine fibroids are found in approximately 2.7% to 10.7% of pregnant women, but in most cases the pregnancy progresses without any problems. 

However, fibroids can grow during pregnancy and this can cause several problems.  

Symptoms 

pain 

It is said that the frequency of pain increases when the size increases to 5cm or more.  

thrombosis 

The uterus and uterine fibroids that grow with pregnancy can compress blood vessels, slowing blood flow and causing blood clots in the blood vessels. This can lead to serious conditions such as venous thrombosis of the lower limbs and pulmonary infarction.  

abortion 

Although pregnancy can occur and implantation can occur, uterine fibroids can cause blood flow problems, resulting in miscarriage. It is said that approximately 7% of repeated miscarriages are caused by uterine fibroids. 

What is the effect of uterine fibroids during pregnancy on childbirth?

Risks of uterine fibroids 

• Threatened miscarriage/preterm birth
• Abnormal fetal position
• Placenta previa
• Premature placental detachment
• Abnormal amniotic fluid volume
• Pregnancy hypertension syndrome
• Water breaks in early stage

As uterine fibroids grow larger during the early to mid-stages of pregnancy, they can cause pain and uterine contractions, and the above complications (problems during pregnancy) increase. 

Threatened miscarriage 17.1-25.9%, threatened premature birth 16.3-39.9%, premature rupture of membranes 7.3%, premature birth 9.3-20%, miscarriage, placental abruption, intrauterine growth retardation, etc. Whether or not a miscarriage is caused by uterine fibroids is determined by a doctor’s comprehensive judgment, but in cases of repeated miscarriages, uterine fibroids are often suspected.

Uterine fibroids during pregnancy. Is there a chance of miscarriage?

Uterine fibroids are a disease that many women suffer from, but it is said that pregnancies complicated by uterine fibroids (pregnancy while having uterine fibroids) account for approximately 1.4%-3.9% of all pregnancies. 

Pregnancy complicated by uterine fibroids carries risks throughout pregnancy, childbirth, and the postpartum period. 

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If I find I have uterine fibroids while pregnant, do I need surgery?

In most cases, active treatment for uterine fibroids is not performed during pregnancy, but symptomatic treatment and monitoring are performed instead. 

However, in cases where the pregnancy is unlikely to continue due to large fibroids, or when fibroids have degenerated due to circulatory or nutritional disorders and local symptoms (pain) are present, enucleation may be performed. However, this too becomes difficult to perform after the 12th week of pregnancy. 

In most cases, symptoms can be controlled with symptomatic treatment while the pregnancy progresses closely. 

Recently, it is possible to accurately determine the size and location of fibroids using ultrasound diagnosis, and even if fibroids are present, they may not affect pregnancy. 

Do women with uterine fibroids have to give birth by Caesarean section?

 The decision to have a Caesarean section or vaginal delivery is made in the final stages of pregnancy after examining the size, location, and number of uterine fibroids, the size and position of the baby, and the position of the placenta. 

In the case of a cesarean section, there are circumstances in which the baby is in an abnormal position, the placenta is in an abnormal position, the muscle layer is difficult to stretch, etc. In addition, after childbirth, there is a possibility of increased bleeding due to poor uterine contraction.

There is also a method to remove fibroids during a Caesarean section, but the policy varies depending on the doctor, so be sure to check. If you have had surgery to remove uterine fibroids before pregnancy, you will be treated the same as a pregnant woman who has had a Caesarean section before, as there is a scar on the uterus, and the method of delivery will often be a Caesarean section.

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Changes in uterine fibroids during pregnancy

In the later stages of pregnancy, the baby often settles into a head-down position, but depending on the location of the uterine fibroids, abnormal fetal position such as breech presentation may occur. 

Do uterine fibroids shrink or grow?

Uterine fibroids are affected by female hormones. Female hormones, which are normally secreted to maintain pregnancy, can also cause changes in uterine fibroids. In fact, it is said that about 20% of pregnant women experience an increase in uterine fibroids during pregnancy, and in most cases, they either get a little bigger or remain almost the same. There are also cases where uterine fibroids get smaller during pregnancy. 

Is 6cm ok?

It is difficult to generalize, but in the pre-pregnancy situation, if the fibroids are over 7cm in size, there are symptoms such as dysmenorrhea or menorrhagia, or they may be the cause of infertility, treatment such as surgery is often considered.

On the other hand, hormone therapy cannot be performed during pregnancy, and surgery is avoided as much as possible, so the condition is often monitored. Therefore, if the uterine fibroid is 6 cm during pregnancy, it will likely be monitored. Some women have vaginal births when the fibroid is 12 cm, so it is necessary to consult with your doctor and monitor the condition. If the pain is severe, treatment will be given to relieve the symptoms using painkillers that do not affect the baby. 

Do uterine fibroids during pregnancy affect the shape of your belly?

Before pregnancy, if uterine fibroids grow to the size of a baby’s head, the abdomen may swell and appear pregnant. This is a common symptom of subserosal fibroids that form on the outside of the uterus.

Some pregnant women may worry that having uterine fibroids will change the way their stomach protrudes, but unless they are giant fibroids, they will not be noticeable. However, in the later stages of pregnancy, you may feel a tingling sensation in your expanding stomach. 

Do uterine fibroids cause pain during pregnancy?

Many women with uterine fibroids go through pregnancy without any problems, but if the fibroids grow rapidly during pregnancy, the frequency of pain increases. 

In such cases, you should consult your doctor and they may prescribe symptomatic treatment to relieve the symptoms, such as using painkillers that will not affect the baby in the womb. 

Can uterine fibroids cause heavy bleeding during pregnancy?

If uterine fibroids grow as the uterus grows during pregnancy, they may cause abdominal pain and bleeding. This can lead to miscarriage or premature birth, so care should be taken. 

If you experience bleeding, painkillers will be used for pain and hemostatic agents will be used to stop the bleeding, but first of all it is important to rest and seek treatment for miscarriage or premature birth. 

Check with NIPT (new type prenatal testing)

When looking at symptoms of pregnancy complicated with uterine fibroids, you will often see words like risk, pregnancy loss, miscarriage, premature birth, and placental abruption. However, not all uterine fibroids have such effects. 

Advances in medical technology and ultrasound examination techniques have made it possible to check the exact size and location of uterine fibroids. If you undergo regular prenatal checkups and monitor the progress of your pregnancy, small uterine fibroids are not a scary disease. There are many pregnant women who have successfully conceived and given birth while undergoing infertility treatment and uterine fibroid treatment at the same time, and many who have successfully given birth vaginally despite having uterine fibroids. 

Even if you have uterine fibroids while pregnant, there is no need to worry about an increased chance of the baby having abnormalities, but I think many pregnant women are concerned about the condition of their baby. 

Recently, the number of facilities performing highly accurate NIPT (non-invasive prenatal testing) has been increasing. 

NIPT (non-invasive prenatal testing) is a test that checks for chromosomal abnormalities such as  trisomy 21 (Down syndrome) , trisomy 18 , and trisomy 13 in the fetus using blood drawn from the mother .

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summary

Pregnancy complicated with uterine fibroids can be a very worrying factor for pregnant women. However, although it is necessary to be careful, as long as you regularly attend prenatal checkups, it is not a disease that you need to worry too much about. 

Uterine fibroids have a wide variety of symptoms, and while many people do not even realize they have them, there are also many people who suffer from severe symptoms. If you are hoping to become pregnant, have heavy periods, or are having difficulty getting pregnant, it is a good idea to visit your nearest gynecologist. Mothers who are pregnant with uterine fibroids should obtain the correct information, not worry too much, and enjoy a fun and comfortable pregnancy.

【References】 

• Mitsuhiro Sugimoto, Junko Nakagawa. Treatment of pregnancy complicated by tumors: uterine fibroids. Obstetrics and Gynecology 2003
• Exacoustos C, Rosati P : Ultrasound diagnosis of uterine myomas and complications in pregnancy. Obstet Gynecol
• Yuji Hiramatsu –  Treatment of pregnant women with gynecological tumors: Uterine fibroids (2007)