Uterine fibroids are the most common abnormality of the uterus. Can these
benign tumors cause a miscarriage. An excellent new study has given us some answers. Stay tuned
Each year, a million women in the USA have a miscarriage. About one in every five women have
fibroids. Fibroids are benign growths that arise from the muscle cells of the uterus.
Fibroids start as one cell but can grow larger. Sometimes much larger. Some fibroids grow
inside of the uterine cavity, some grow in the muscle wall of the uterus
and some grow on the outside of the uterus. It is possible to have one fibroid or
multiple fibroids and in one location or in multiple locations.
Recently, I released an episode of InfertilityTV in which I reviewed the
results of a study which found that any alcohol use by a person during pregnancy
will increase the risk for miscarriage. That study was part of a larger research project
called Right From The Start or RFTS. Today, I will discuss the results of another study from RFTS.
In this study, over 5000 pregnant people in the USA were recruited either before they became
pregnant or early in the first trimester. Each of these people had an ultrasound to
look for fibroids.11% of the people were found to have one or more uterine fibroids.
The study compared how often miscarriages occured in the group that had fibroids
compared to the group that didn’t. They found that the risk for miscarriage was the same
in both groups. Overall about 11% of the pregnancies miscarried in each group.
Next, the researchers compared people that had no fibroids,
to those with one fibroid and then those with two or more fibroids. Again,
they did not find any increase in the risk miscarriage based on the number of fibroids.
In order to look at the effect of the size of the fibroids, they did two different calculations.
They looked at the total volume of space that the fibroids took up in the uterus and split them into
4 groups. They also divided the patients into 4 groups based on the size of the largest
single fibroid. In both instances, there was no difference in the miscarriage risk
based on the individual or total size of fibroids in the uterus.
Finally, they looked at the location of the fibroids in the uterus and divided them into
three groups. Fibroids on the outside of the uterus, fibroids in the muscle wall of the uterus
and those that appeared near to the uterine cavity. Again, no difference was found.
I will add my own opinion here. Using only an ultrasound, as they did in this study,
it is sometimes difficult to see fibroids that are inside the uterine cavity
or those that may be causing distortion of the uterine cavity, especially during pregnancy.
These types of fibroids, however, may be the type that are most likely to cause miscarriage.
A better way to look at these types of fibroids is to do an ultrasound in which the doctor first
squirts fluid into the uterine cavity. This is called a saline ultrasound or hysterosonogram.
Another method is to look inside the cavity directly using a hysteroscope.
I dont think this study can draw any firm conclusions about these types of fibroids.
My InfertilityTV recommendation is that fibroids that are in the muscle wall of the uterus
or on the outside do not need to be removed. These fibroids do not seem to increase the
risk for miscarriage and removing them will not reduce the risk for having a miscarriage.
It is still reasonable, however, to remove fibroids
that occupy the uterine cavity or causes the shape of the uterus to be distorted.
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