Uterine fibroids do not always cause obvious symptoms (they can be asymptomatic - see fibroids symptoms). Consequently the first time a pregnant woman may discover she has them is when she goes for her first routine prenatal scan. Fortunately most fibroids are harmless and cause few complications during pregnancy. Some women diagnosed with fibroids before becoming pregnant may worry that pregnancy will cause the fibroid(s) to grow more rapidly; particularly as excess estrogen hormones are a known risk factor. Recent research indicates that most fibroids (80 percent) do not actually increase in size during pregnancy and those that do, shrink back to their pre-pregnancy size again after childbirth. If a fibroid is going to grow, it is likely to do so in the first trimester of pregnancy.
It is estimated that one in every 1,000 pregnant women has fibroids although this figure may be underestimated. Fibroids are more likely to occur in women experiencing a pregnancy after 35 and those who underwent infertility treatment. It is estimated in both categories that the incidence rate could be as high as between 12 to 25 percent.
Many women with fibroids notice increased abdominal pain when they become pregnant. This is due to condition technically known as red degeneration of fibroids. It is caused by the hemorrhage of blood into the tumor which starves the surrounding tissues. It affects about 10 percent of all women with fibroids during pregnancy. Most commonly it occurs in the last trimester or when fibroids are over 5cm in size. Symptoms may appear similar to those of a twisted ovarian tumor or acute appendicitis. That is: sudden pain, a general feeling of unwellness and fever. The tongue may be dry and the pulse races. Constipation and tenderness in the area of the abdomen where the fibroid is located are also signs. Although the pain is unpleasant, it is not usually anything to worry about. Do always report any pain or bleeding to your pregnancy healthcare team. Bed rest for 3 or 4 days in addition to safe pain relievers (analgesics such as ibuprofen) is usually prescribed. See also: Pelvic pain during pregnancy.
As the baby grows and space is restricted in mother's body, fibroids may cause an uncomfortable pressure as they squeeze on nearby organs. A sharp pain in the legs and lower back may occur if nerves become restricted and compressed. If you were prone to breast fibroids before pregnancy, you may find they increase in number during pregnancy.
Type, Size and Location
Receiving an accurate fibroids diagnosis is important as this will provide information on the type of growth, its size, how many there are, and where they are located. One study carried out in 1993 investigated 12,500 pregnant women with fibroids and discovered in the vast majority of cases (88 percent) only one fibroid was present. They reported an increased risk of pain and bleeding during pregnancy in women with large fibroids measuring 200cm3 volumes or more, or when the fibroid was located underneath the placenta. For this reason, knowing as much as possible about the type(s) of fibroid present will help a physician predict how it is likely to react during pregnancy. For example, submucosal fibroids, the least common type, can grow through the lining of the uterus and make the cavity inside the womb too small for the baby to grow in over 9 months. In fact nearly 40 percent of pregnancies with submucosal fibroids end up in miscarriage (often before the woman even knows she is expecting). Subserosal fibroids project out of the uterus wall and can grow quite large. Although they do not affect space inside the womb, they are more likely to result in abdominal pain or pressure. Pedunculated fibroids are attached to the uterus by thin stalks, they do not tend to cause problems in pregnancy although if the stalks twist (fibroid torsion), they can cause a severe sharp pain.
Less Common Complications
The chance of spontaneous miscarriage is greater in women with fibroids. Research indicates that multiple fibroids increase the chance by nearly 24 percent compared to a single fibroid at 8 percent. The location of the fibroid is important as submucosal fibroids for example can increase the rate of miscarriage significantly. Why fibroids should increase the chance of miscarriage is not clear but it may be because the tumors increase irritation of the uterine or they have a compressive (squeezing) effect on the womb or they may reduce blood supply to the developing placenta and fetus.
Bleeding In Early Pregnancy
The location of the fibroid tends to be the most important factor here. The closer the fibroid is to the placenta, the more likely bleeding is to occur in the first trimester.
Very occasionally fibroids can cause placental abruption, where the placenta separates early from the wall of the uterus. In most cases the abruption (separation) is not total so the baby can still receive an adequate supply of food and oxygen from the mother. However if the abruption is severe, an emergency C-section delivery may be required. There are conflicting reports on the risk of placental abruption with fibroids; some research indicates it could be 3 times higher than women without tumors.
This has not been hugely researched but initial findings indicate that the risk of placenta previa is twice as high in women with fibroids.
Fibroids may slightly increase the woman's chance of pre-term labor. That is a labor which starts anytime after week 20 and before the end of week 37. If labor is premature it is likely to be 2 to 3 weeks early which will cause little if any harm to the baby. Again location of the fibroid(s) is important - the closer they are to the placenta, the higher the risk for preterm labor. Interestingly, fibroids do not appear to be a risk factor for preterm premature rupture of membranes (PPROM). In fact studies indicate fibroids can reduce the risk of PPROM.
Fetal Growth Restriction
Intrauterine growth restriction and fetal abnormalities are not normally caused by fibroids. In rare instances however submucosal fibroids can restrict space in the womb cavity leading to some fetus deformities such as an abnormal twisting of the baby's neck (torticollis) or compression of its skull (dolichocephaly).
Childbirth And Delivery
If you have fibroids, discuss delivery options with your doctor well in advance of your due date. If fibroids are particularly large or located in an awkward place this may rule out a safe vaginal delivery. Your doctor may opt for a C-section instead. There is a slight increase in risk in postpartum bleeding (hemorrhage) in women with fibroids, so this will need to be monitored.
How Are Fibroids Treated During Pregnancy?
It is usually diagnosed by ultrasound scan during pregnancy, which is the safest procedure. Generally treatment is to do nothing and to monitor any growth during subsequent prenatal scans.
Fibroids pain is generally managed by best rest, drinking plenty of liquids and taking safe analgesic painkillers (only when prescribed by a doctor). Nonsteroidal anti-inflammatory drugs should be used with caution, particularly if taken for longer than 48 hours in the third trimester when it is associated with a variety of medical complications including oligohydramnios.
Most experts agree that surgery for fibroids should be avoided where possible during pregnancy, especially in the first two trimesters. If necessary, however a myomectomy (see fibroids treatment) can be safely performed in the first and second trimester of pregnancy. It will only be considered where:
• Pain is intractable and chronic probably resulting from a subserosal or pedunculated fibroid.
• Where a fibroid is growing rapidly.
• Where a fibroid over 5cm which is located in the lower part of the uterine.
This is a safe procedure, even in pregnancy, but it can result in the necessity of a C-section delivery due to concerns about uterine ruptures. Uterine artery embolization (UAE) is another possible procedure, but it may not recommended for women who wish to retain their fertility. See also, can fibroids grow back?
Will A Previous Fibroids Surgery Affect My Pregnancy?
The removal of small fibroid tumors by surgery is not likely to affect any future pregnancies. The only possible issue is where extensive surgery was carried out to remove large tumors. This could weaken the uterus to the point where it cannot handle a regular labor. Your doctor may discuss the possibility of an elective C-section. It is also worth becoming familiar with the early signs of labor in case contractions start early.
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