Do Fibroids Affect Fertility, Pregnancy and Birth?

18 Jan Do Fibroids Affect Fertility, Pregnancy and Birth?

Fibroids are the most common benign growth arising from the muscle of the uterus in women of reproductive age, affecting up to 40% of women. As fibroids are responsive to the female hormones estrogen and progesterone, they can grow in size over time during a woman’s reproductive life, until menopause when fibroids usually stop growing and may even shrink. While many of these fibroids do not cause symptoms, some can grow large enough to cause heavy periods, pressure within the pelvis and impact fertility. Fibroids are frequently diagnosed when women have ultrasound scans performed during their fertility journey and at routine pregnancy scans.  

What effect do fibroids have on a woman’s fertility? What problems can they lead to in pregnancy? How about at the time of birth? 

Fibroids and fertility 

In general, fibroids do not affect fertility unless they grow in a way that distorts the endometrial (uterine) cavity. This is where embryos implant and grow. If the fibroid is submucosal, it is more likely to distort the cavity and this in turn reduces the likelihood of embryo implantation. The further away the fibroid is from the cavity, the less impact it has on fertility. However, some intramural and subserosal fibroids can be so large that they also distort the entire uterus and its cavity.   

A submucosal fibroid can be resected (surgically removed) through a hysteroscope (a thin telescope through the cervix), thereby improving fertility through optimising the conditions of the endometrial cavity and its suitability for implantation. The main treatment option for large intramural and subserosal fibroids is a myomectomy (either laparoscopically or through traditional open procedure). Non-surgical options such as uterine artery embolization (UAE) and MRI guided focused ultrasound (MRGFUS) are not recommended prior to pregnancy, they aim to shrink fibroids rather than remove them entirely and the safety of pregnancy following these procedures is uncertain.   

The link between having fibroids in general and recurrent miscarriages is more difficult to establish due to confounding factors. Increasing age is associated with an increased risk of fibroids, in addition to reduced fertility and miscarriage. As fibroids may not always be the sole contributor to reduced fertility and miscarriage, other potential factors require consideration through a thorough assessment.  

Fibroids and pregnancy 

Fibroids are frequently detected incidentally during routine pregnancy ultrasound scans. In the majority of cases, they are innocent bystanders and do not cause problems during pregnancy.  

Some fibroids are large or grow quickly in size, especially in the first trimester due to the hormonal surge associated with pregnancy. This rapid growth can lead to reduced blood supply and cell death (degeneration) within the fibroid, which in turn cause pain. This is the most common complication of fibroids during pregnancy. Treatment is normally conservative with hospital admission for pain medications and monitoring.  

Other less common complications such as miscarriage, bleeding, fetal growth restriction and preterm birth are more likely with larger or multiple fibroids located behind the placenta or distorting the uterine cavity.  

Fibroids and birth 

Again, fibroids in general do not affect labour and birth. Fibroids which are large and low in position (such as within the cervix) may obstruct labour (cervix either not dilating or baby’s head not coming down) and necessitate Caesarean delivery. Larger fibroids are also more likely to cause malpresentation, that is baby is not ‘head down’. This will also lead to Caesarean delivery. Large fibroids may also be associated with more bleeding during or after a delivery, as these fibroids can decrease the force and coordination required for the uterus to contract and stop bleeding. Your obstetrician or midwife will usually be prepared and anticipate these medical emergencies. It is not recommended to have a myomectomy performed at the time of Caesarean delivery as the pregnant uterus has significantly more blood supply than its usual non-pregnant state, and this can lead to significantly more blood loss.  

For women who have had a myomectomy in the past, a planned Caesarean delivery may be recommended if the fibroids removed were large, numerous and deep within the muscle of the uterus. This is a common situation as only large fibroids necessitate removal when they become symptomatic. Smaller fibroids are usually not symptomatic and therefore not removed. Having labour contractions along the scar increases the risk of uterine rupture, a life threatening pregnancy complication for both mother and baby. Caesarean delivery is scheduled before labour begins, the timing depending on how extensive the myomectomy and uterine reconstruction was.  

While fibroids are common incidental findings during the fertility and pregnancy journey, they are most likely innocent bystanders that will not cause problems. It is important, however, for your doctor to be aware of fibroids that may potentially cause complications. You should be able to discuss these issues with your pregnancy care providers, be it your GP, obstetrician, gynaecologist or midwife.