A molar pregnancy, also known as a hydatidiform mole, is a rare condition that arises during pregnancy. It occurs when there is an abnormal combination of genetic material from the egg and sperm during fertilization. There are two main types of molar pregnancies:
- Complete Molar Pregnancy: In this type, an abnormal placenta forms without an embryo.
- Partial Molar Pregnancy: In a partial molar pregnancy, an abnormal placenta forms along with an embryo that is usually not viable due to significant genetic abnormalities.
Molar pregnancies typically result from abnormal fertilization, leading to an imbalance of genetic material from the egg and sperm. In complete molar pregnancies, either one or two sperm fertilize an empty egg, resulting in genetic material solely from the paternal side. In partial molar pregnancies, maternal genetic material is present, but two sperm fertilize the egg, leading to an abnormal number of paternal chromosomes (69 total chromosomes, instead of the usual 46).
While molar pregnancies are relatively rare, certain factors can increase the risk of experiencing one. For example, individuals under 20 and those over the age of 35 have a higher risk of molar pregnancy. Additionally, having had a molar pregnancy in the past increases the chances of having another one, with the risk being higher after a complete molar pregnancy.
Symptoms of a molar pregnancy may initially resemble common pregnancy symptoms, such as a missed period and breast tenderness. However, as the condition progresses, symptoms can become more concerning. These symptoms may include intense nausea, vomiting, vaginal bleeding, lower abdominal pain, an enlarged uterus, and in some cases, signs of preeclampsia or hypertension. Elevated levels of the pregnancy hormone hCG can lead to severe nausea and vomiting, known as hyperemesis gravidarum.
If a molar pregnancy is suspected, diagnostic measures may include abnormal bleeding, elevated hCG levels, or an abnormal first-trimester ultrasound result. Sometimes, partial molar pregnancies are diagnosed through pathology after a seemingly typical first-trimester miscarriage.
The treatment for a molar pregnancy often involves a procedure called dilation and curettage (D&C), which removes the molar pregnancy tissue from the uterus. This procedure is typically performed if the molar pregnancy does not spontaneously miscarry. Following the D&C, hCG levels are monitored for several weeks or months to ensure that no remnants of the molar pregnancy remain.
It is important to avoid getting pregnant during the follow-up period after a molar pregnancy, as a new pregnancy can make it difficult to detect any potential complications or the development of cancerous growth.
In rare cases, complications may arise if a molar pregnancy is left untreated. These complications can include anemia from vaginal bleeding, hyperemesis gravidarum, abnormal thyroid function, ovarian theca lutein cysts, and preeclampsia. If some tissue from the molar pregnancy persists in the uterus after treatment, it can develop into gestational trophoblastic neoplasia (GTN), which may require chemotherapy and surgery. Even more rarely, the molar tissue can develop into choriocarcinoma, a type of cancer that may necessitate chemotherapy and other cancer-fighting treatments.