Pregnancy is always incredibly difficult, even if it happens very early on. A molar pregnancy, though rare, is one of the reasons a pregnancy might end prematurely. Learn more about what a molar pregnancy is and what causes it.
What is a molar pregnancy?
In a molar pregnancy (also called a hydatidiform mole), the tissue that’s meant to become the placenta overgrows, becoming a mass of cysts.
In some cases there is no accompanying embryo, while in other cases, a partially formed but not viable fetus or some identifiable embryonic or fetal tissue is present. This is called a partial molar pregnancy.
Complete molar pregnancy vs. partial molar pregnancy
The cause of a molar pregnancy is an abnormality during fertilization, likely when two sets of chromosomes from the father become mixed in with either one set of chromosomes from the mother (partial mole) — or none of her chromosomes at all (complete mole).
Most molar pregnancies are discovered within weeks of conception, and unfortunately all end in miscarriage.
How common are molar pregnancies?
Luckily, molar pregnancies are relatively rare, occurring only in 1 out of 1,000 pregnancies.[1]
Who is most at risk of having a molar pregnancy?
Women who are at slightly increased risk for a molar pregnancy include those over the age of 35, those under age 20 and those who have had multiple miscarriages.
What are the symptoms of a molar pregnancy?
The symptoms of a molar pregnancy can include:
- A continuous or intermittent brown or bright red, bloody discharge (the most common symptom)
- Vaginal bleeding
- Severe nausea and vomiting
- Uncomfortable cramping
- Unexplained weight loss
- High blood pressure
- Larger than expected uterus
- Doughy uterus (rather than firm)
- Absence of embryonic or fetal tissue (as seen on ultrasound)
- Excessive levels of thyroid hormone
- The passage of an oval-shaped, grape-like cyst called a trophoblast from the vagina (or multiple cysts)
- Ovarian cysts (detected by your doctor)
- Preeclampsia (usually not discovered until you make an appointment with your doctor)
Should you be concerned if you think you've had a molar pregnancy?
A molar pregnancy is a risk factor for the development of persistent gestational trophoblastic neoplasia (GTN). Also known as gestational trophoblastic disease, this condition is when left-behind placental tissues continue to grow.[2]
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Very occasionally, that can lead to a rare form of cancer known as choriocarcinoma. Fortunately, GTN and choriocarcinoma are extremely uncommon conditions, with the latter occurring in only 1 out of every 40,000 pregnancies.
What you can do if you think you're experiencing a molar pregnancy
Call your doctor if you experience any of the symptoms listed above. Since some of these symptoms can be difficult to differentiate from normal early pregnancy signs and symptoms , you should trust your instincts. Many completely normal pregnancies include some spotting and cramping, and most include nausea. If you think something's wrong, talk to your provider — if only to get some much-needed reassurance.
Your practitioner will likely do an ultrasound and blood work (to look at hCG levels), and he or she may want to run a chest X-ray or MRI of your abdomen. If you do have a molar pregnancy, the abnormal tissue must be removed via a dilation and curettage (D&C), a procedure that usually takes 15 to 30 minutes. Your doctor will use a speculum (the same tool used during a routine pelvic exam) to see and dilate your cervix, then remove the tissue.[3]
Follow-up to check your hCG levels is crucial to make sure that abnormal tissue doesn’t grow back or progress to choriocarcinoma. Luckily, the chance of a treated molar pregnancy turning malignant is extremely rare.
Getting pregnant again after a molar pregnancy
Yourpractitioner will probably suggest that you not get pregnant for six months to a year. Women who try to conceive sooner are at greater risk for having another molar pregnancy.
The good news is that otherwise, having one molar pregnancy is not an indication that you have a higher risk for having another one. Only 1 to 2 percent of women who have had one molar pregnancy go on to experience a second.
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