Topics of Interest

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.
Obstetrical and Gynecological Survey.2001;56:483-91.

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.

Fibroids (leiomyomas) at routine second-trimester ultrasound examination and adverse obstetric outcomes

Journal: Obstet Gynecol. 2010 Nov;116(5):1056-63.

Authors: Stout MJ, Odibo AO, Graseck AS, Macones GA, Crane JP, Cahill AG.

Study from: Washington University, St Louis, Missouri

Problem: Numerous studies have been conducted to see if the presence of fibroids during pregnancy affects the outcome of the pregnancy or the health of the baby. Most of these studies have been poorly designed and have failed to answer these important questions.

Study: Between 1990 and 2007, 64,047 consecutive pregnant women had a routine second-trimester ultrasound and the presence or absence of fibroids was routinely noted. The outcomes of the pregnancies in women with fibroids were compared to pregnancies in women without fibroids.

Results: Fibroids were seen on ultrasound in 3.2% of all pregnant women. The following findings were noted.

  • Babies were breech in 5.3% of women with fibroids compared with 3.1% of women with no fibroids.
  • Placenta previa (placenta partially or completely blocking the cervix) was found in 1.4% (fibroids) compared with 0.5% (no fibroids).
  • Placental abruption (placenta separating from the uterine wall, causing bleeding) was found in 1.4% (fibroids) compared with 0.7% (no fibroids).
  • Preterm rupture of membranes was found in 3.3% (fibroids) compared with 2.4% (no fibroids).
  • Preterm birth less than 37 weeks was found in 15.1% (fibroids) compared with 10.5% (no fibroids) and at less than 34 weeks was 3.9% (fibroids) compared with 2.8% (no fibroids).
  • Intrauterine fetal death in women with a baby with growth restriction (small baby) was found in 3.9% (fibroids) compared with 1.5% (no fibroids).
  • Cesarean delivery was performed in 33% (fibroids) compared with 24% (no fibroids).

Authors’ Conclusions: Women with fibroids are at low risk for obstetric complications compared with women without fibroids.

Dr. Parker’s Comments: Two other excellent studies have been published previously on this topic: one showed absolutely no increased risk of complications for women who became pregnant with fibroids; the other showed very minimal increased risks.

This new study shows very minimal increased risks: a 0.9% increased risk of the placenta blocking the cervix; a 0.7% increased risk of placental separation; a 0.9% increased risk of early ruptured membranes; a 4.6% increased risk of delivery before 37 weeks (where the babies usually do extremely well) and a 1.1% increased risk of delivery before 34 weeks (most babies also do well, but need neonatal ICU care); and, a 1.4% increased risk of fetal death in babies who were very small at birth. The new study was conducted at an urban referral hospital and the women had a high rate of alcohol use, smoking and high blood pressure, so the results might be even better in a healthier group of women.

The findings of the three well-performed studies show an extremely small increased risk, which ought to be reassuring for women with fibroids who wish to become pregnant. It should also be noted that, based on a review of the literature I did for a chapter on fibroids to be published in Berek and Novak’s Gynecology textbook, in the past 30 years there have been only four babies born in the world who have been reported to have birth defects related to the presence of fibroids during pregnancy. This is also very reassuring news.

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.

William H. Parker, MD
Clinical Professor, Reproductive Medicine, UC San Diego School of Medicine

Page last updated: January, 2018

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Disclaimer: The ideas, procedures and suggestions contained on this web site are not intended as a substitute for consulting with your physician. All matters regarding your health require medical supervision.

Fibroid Doctor William H. Parker

Dr. William H. Parker is a board-certified Fellow in the American College of Obstetricians and Gynecologists. Dr. Parker is an internationally recognized expert in fibroid surgery and research. Based in San Diego, California, he is considered one of the best fibroid surgeons for abdominal and laparoscopic myomectomy in the United States and abroad. He has been chosen for Best Doctors in America and Top Doctors every year beginning in the late 90's.

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