How do fibroids affect each trimester of pregnancy differently?


When considering becoming pregnant, just hearing the word “fibroids” often strikes fear into women. While most women have little to worry about concerning the connection between the presence of uterine fibroids and pregnancy complications, what actually does happen to a woman and her developing fetus when she carries both a pregnancy and fibroids? 

The average length of a full-term pregnancy is 40 weeks from the first day of the mother’s last menstrual period. This time is divided into three trimesters — that is, sections of the pregnancy — with each trimester having its own characteristics, changing as the baby grows. It is important to note that many women who have fibroids have no related issues at all through the duration of their pregnancies. 

First Trimester 

During the first trimester, the embryo develops from a clump of cells into a more recognizable, human shape. While body systems are forming and basic limbs appear, the fetus remains tiny. This is the only trimester in which fibroids are known to grow. Even then, only one third grow in the first trimester, with the rest retaining their pre-pregnancy size. Estrogen is a hormone that rises significantly during the first trimester of pregnancy. In addition, blood volume increases. Both these factors can contribute to the growth of any fibroid(s) already present. 

It is also vital that your gynecologist be fully informed about your fibroid(s)’ presence and location, as risk factors correlate with “an increased rate of spontaneous miscarriage, preterm labor, placenta abruption, malpresentation, labor dystocia, cesarean delivery and postpartum hemorrhage.” 

It seems that the number of fibroids present as well as their location are more an issue in creating pregnancy complications than the size of the fibroid(s). It is suspected that the fibroids cause “increased uterine irritability and contractility and compromise the blood supply of the developing placenta.” In instances where the placenta implants close to the fibroid, there is an increased risk for bleeding. 

Second Trimester 

As the fetus grows, things start becoming crowded in there and space becomes an issue. While in a regular pregnancy the baby starts pushing on internal organs, with fibroids, it’s the baby AND the fibroid(s) putting pressure on everything around them. This can result in back or leg pain that may feel like sciatica. 

Researchers are stating that fetal growth doesn’t seem to be affected by the presence of fibroids. While rare, large submucosal fibroids can create a problem of space in the uterus, causing dolichocephaly (lateral compression of the fetal skull), torticollis (abnormal twisting of the neck) and limb reduction defects. 

Other more severe but rare complications can include degeneration and fibroid torsion. The former of these refers to a fibroid that suddenly twists, causing severe pain and/or cramping, while the latter describes a rare situation generally that can occur when fibroids are larger than five centimeters in size. These larger fibroids can start to degenerate through a process that releases prostaglandins, a substance that causes contractions. When prostaglandin levels rise to higher levels, it can result in spontaneous miscarriage. 

Third Trimester 

Also interesting to note is that fibroids may actually decrease the risk of Preterm Premature Rupture of Membranes (PPROM). The flip side of this is that pregnant women with fibroids are significantly more likely to go into labor earlier than what is considered healthy. The chances of placental abruption are three times higher and placenta previa are double the norm. 

Women with fibroids who are pregnant are unfortunately also six times more likely to need a cesarean section to give birth than women without fibroids. Depending their location, fibroids may block the birth canal or they can interfere with proper, productive contractions, slowing the birth and thus putting the baby at risk. Because of this risk, women nearing their third trimester should make themselves informed about the process of a cesarean delivery and recovery afterward. Being prepared for any eventuality improves birth outcomes and recovery. 

Connect with a doctor you trust 

Even though having a completely standard pregnancy and birth – even with fibroids – is possible and does happen, the potential complications are serious. Because of this, it’s even more vital for women with fibroids to connect with a doctor they trust and stay on top of appointments, tests and medical directives. So for not only safety and health but also peace of mind, find that doctor and stick with her/him all the way through to the birth, and enjoy your new baby!