GUIDE
A molar pregnancy (hydatidiform mole) occurs when abnormal tissue grows in the uterus instead of a healthy pregnancy. It involves an abnormal fertilization event that produces a mass of grape-like tissue.
Molar pregnancies are rare, affecting about 1 in 1,000 pregnancies. While the diagnosis is frightening, molar pregnancies are treatable with D&C and require follow-up hCG monitoring to ensure complete resolution.
Be prepared from day one
A molar pregnancy is a type of gestational trophoblastic disease — an abnormal fertilization event that leads to the growth of non-viable tissue in the uterus. Instead of a normal pregnancy developing, the placental tissue grows abnormally into a mass of cyst-like structures that resemble a cluster of grapes.
There are two types. A complete molar pregnancy occurs when an egg with no genetic material (or no functional DNA) is fertilized by one or two sperm. The result has only paternal chromosomes — there is no embryo, only abnormal placental tissue that grows rapidly. A partial molar pregnancy occurs when a normal egg is fertilized by two sperm simultaneously, resulting in 69 chromosomes instead of the normal 46. Some embryonic tissue may form but cannot develop into a viable fetus.
Molar pregnancies are rare, affecting about 1 in 1,000 pregnancies in the United States. Risk factors include being under 20 or over 40, a history of previous molar pregnancy, and certain geographic and ethnic factors (higher rates in Southeast Asia and some parts of South America).
Many of these symptoms overlap with normal early pregnancy or other conditions. A combination of symptoms — especially very high hCG with abnormal ultrasound findings — points toward a molar pregnancy.
Molar pregnancy is typically diagnosed via ultrasound combined with hCG blood levels. On ultrasound, a complete mole appears as a mass of cystic structures within the uterus — often described as a snowstorm pattern — with no embryo. A partial mole may show an abnormal-appearing placenta alongside some embryonic tissue.
hCG levels in molar pregnancies are often dramatically elevated — sometimes in the hundreds of thousands, far higher than expected for the gestational age. This very high hCG is what causes the severe nausea and, in some cases, early preeclampsia and thyroid stimulation.
The diagnosis is confirmed after D&C by examining the removed tissue under a microscope (histopathology). This examination distinguishes between a complete and partial mole and rules out other conditions.
The primary treatment for a molar pregnancy is suction dilation and curettage (D&C) — a surgical procedure to remove the abnormal tissue from the uterus. This is typically performed under anesthesia and takes about 15 to 30 minutes. Most people go home the same day.
After the D&C, the critical phase begins: hCG monitoring. Your blood will be drawn weekly to track hCG levels as they fall toward zero. In most cases, hCG reaches undetectable levels within 8 to 12 weeks after treatment. Once hCG is undetectable, monthly monitoring continues for 6 months (partial mole) or 12 months (complete mole) to ensure levels remain at zero.
If hCG levels plateau, rise, or fail to reach zero, further treatment is needed. This may involve additional D&C, chemotherapy, or both. The good news is that gestational trophoblastic neoplasia (the persistent form) is one of the most curable cancers, with success rates above 98 percent with chemotherapy.
After D&C for a molar pregnancy, your hCG levels will be checked weekly until they reach zero, then monitored monthly for 6 months (partial mole) or 12 months (complete mole). This monitoring is non-negotiable — it is the only way to detect persistent molar disease early. Missing blood draws can delay detection of a problem that is highly curable when caught early.
You must avoid pregnancy during the entire hCG monitoring period. A new pregnancy would produce hCG, making it impossible to tell whether rising levels are from a healthy pregnancy or persistent molar tissue. Your provider will discuss contraception options — hormonal methods (pills, IUD, implant) and barrier methods are all appropriate.
A molar pregnancy is a unique and confusing loss. You were pregnant, you had a positive test and symptoms, but the pregnancy was never viable. On top of the grief, you may be anxious about the cancer risk and frustrated by the long monitoring period before you can try again. These emotions are all valid. A therapist experienced in pregnancy loss can help you navigate this complex experience.
Do not miss your follow-up hCG blood draws. If persistent molar tissue develops (gestational trophoblastic neoplasia), it is one of the most curable forms of cancer when detected early — with cure rates above 98 percent. The monitoring period protects you. If your hCG rises, plateaus, or does not reach zero, your provider will investigate promptly.
During the monitoring period, any new symptoms should be reported promptly. Your care team wants to hear from you.
These symptoms require immediate evaluation, whether before or after treatment.
Once your hCG monitoring period is complete and levels have been undetectable for the required time, your provider will give you the green light to try to conceive. The vast majority of people go on to have normal, healthy pregnancies after a molar pregnancy.
The risk of recurrence is about 1 to 2 percent — higher than the general population (0.1 percent) but still very low. In your next pregnancy, your provider may recommend an early ultrasound to confirm normal pregnancy development and may check an hCG level at 6 weeks postpartum to ensure it returns to zero normally.
For related information and support, see our guides on miscarriage signs and support, pregnancy after miscarriage, blighted ovum, bleeding during pregnancy, and high-risk pregnancy.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
