Molar pregnancy: the causes and definition
A molar pregnancy is an abnormal growth of the placental tissue in the uterus as a result of an unfortunate pregnancy.
It happens after the sperm has fertilized the egg and the tissue which should have developed into the placenta in order to sustain the fetus form an abnormal mass. The mass consists of cell clusters resembling a bunch of grapes (hundreds of little bags full of fluid).
A molar pregnancy usually occurs as a result of the situation when a woman has vaginal bleeding in early pregnancy. It also happens when the uterus is larger than normal – in this case, it’s accompanied by ovarian pain and heavy morning sickness and vomiting.
A lot of women diagnosed with molar pregnancy hadn’t even heard of such a thing before. Very few expectant mothers had known about this pregnancy complication. The reason for it lies in the pregnant woman’s age. A future mother younger than 20 or older than 40 has a higher risk of molar pregnancy.
Complete and partial molar pregnancy
There are two main kinds of molar pregnancy: a complete mole and a partial mole. Both of them are a result of an error during the fertilization process. A complete molar pregnancy is more common than a partial mole.
- During a complete molar pregnancy, there is no embryo developing but the placental tissue is growing very fast, forming abnormal clusters. As a rule, it happens because the female egg cells don’t have maternal chromosomes which are inactive or lost. When an egg is fertilized by one or two spermatozoa it leads to a zygote containing only the father’s chromosomes. The ultrasound will show there is no embryo, only placental tissue.
- A partial molar pregnancy means that the egg cell is normal, but it’s been fertilized by two spermatozoa rather than one. It leads to the development of an abnormal embryo which contains too many chromosomes: one set from the mother and two sets from the father. So, there are 69 chromosomes instead of a normal set of 46. That’s why an embryo is developing in the wrong way and eventually dies.
The signs and symptoms of molar pregnancy
The most common symptom of both kinds of molar pregnancy is vaginal bleeding. A complete mole usually leads to a heavier bleeding than a partial mole. During a partial molar pregnancy, there are a few less copious bleedings.
The discharge during vaginal bleeding varies from bright red to dark brown. A future mother usually experiences such a symptom in the 2nd or 3rd month of pregnancy. The blood can contain small grape-like cysts.
Every future mother needs to know that any vaginal bleeding during pregnancy is a cause to pay a visit to her doctor.
Besides a vaginal bleeding, other molar pregnancy symptoms may include:
- Increased size of the uterus – the womb is usually bigger than during a normal pregnancy. During a partial molar pregnancy, the uterus is smaller than usual.
- Increased size of the ovaries. The hCG (human chorionic gonadotropin) level is high.
- Severe nausea and vomiting.
- High blood pressure during the first trimester or in the beginning of the second trimester of pregnancy.
Molar pregnancy risk factors
A complete or partial molar pregnancy is a rare case – about 1 of every 1000 pregnancies.
The factors increasing the risk of a molar pregnancy are:
- Women younger than 20 or older than 40 have a high possibility of a molar pregnancy. The pregnant teenage girls whose egg cells are not mature and who don’t have a regular menstrual cycle and 40-year-old women who have reached the end of their reproductive age are likely to have complications.
- Medical history. If a woman’s had one molar pregnancy her chances of giving birth to a healthy baby are good (1-2% risk of another molar pregnancy). Her next pregnancy will most probably be a normal one, and she’ll bear a healthy child. If a woman’s had two molar pregnancies the odds of a third one are higher – 15-20%.
- Women from South-East Asia (Vietnam, Korea) have a higher possibility of a molar pregnancy. There are some theories why the Asians experience complications more often – most of them are related to the traditional food.
Frankly speaking, health professionals still don’t know for sure why molar pregnancies happen. There are some food-related theories about carotene deficiency (it’s a plant pigment contained in red and orange fruit and vegetables) as a possible reason.
How to diagnose a molar pregnancy?
Doctors usually diagnose this condition with the help of a pelvic ultrasound which shows the presence of cysts in the uterus. A complete molar pregnancy is easier to detect by an ultrasound than a partial mole.
The pregnant women also pass an hCG blood test. The quickly growing placental tissue causes the raised production of hCG.
The women with a partial molar pregnancy usually have a normal or only slightly increased hCG level, so it’s more difficult to detect a mole. In this case, medical experts often misinterpret the symptoms for cancer.
Molar pregnancy hCG levels
When a woman isn’t pregnant there should be no hCG in her bloodstream. During the gestation, hCG production begins on the 8th day after the conception and reaches its highest level on the 60th day – 5000-10000 mIU/ml. If the hCG level remains high after the 12th week doctors suspect a molar pregnancy.
Molar pregnancy ultrasound
It’s the most accurate diagnosing method. An ultrasonic examination usually shows the increased size of the uterus (50% of cases), the absence of an embryo or fetus, the presence of grape-like cysts.
Molar pregnancy treatment
The only outcome of a molar pregnancy is the removal of the abnormal mass from the uterus. A medic performs the procedure called vacuum aspiration.
After the procedure, the hCG level in blood will be monitored for the next 6 to 12 months in order to make sure the hormone is gradually decreasing to a normal level and there is no abnormal tissue left in the uterus.
If the hCG levels don’t lower to normal or even begin to increase again a woman will need additional treatment.
A woman may also decide she doesn’t want to have children and undergo hysterectomy – a surgery to have her uterus removed – instead of a vacuum aspiration.
Risks of a molar pregnancy for a mother
There is a short-term risk that a molar pregnancy develops into gestational trophoblastic disease – a condition when the molar tissue remains in the uterus after a surgery and continues its growth.
Your doctor will most likely find it out early, though, so you’ll get the disease treated with chemotherapy. There is also a small chance the mass will turn into cancer, then more chemo (or even radiation treatment) will be needed. It’s one of the most treatable kinds of cancer which almost always can be cured regardless of the disease that preceded it.
The women who have recently suffered from a molar pregnancy will have to wait for a year before trying to conceive again. They should make sure the abnormal placental tissue won’t return.