Published: December 10, 2008 09:20 am      

Molar pregnancy occurs in oldest, youngest women

DEAR DR. MONA: What is a molar pregnancy, and should I be worried about this? I am trying to get pregnant and one of my friends had this and I am scared. Could you explain? — Bobbie

DEAR BOBBIE: A molar pregnancy is one in which an error in the fertilization process takes place. No obvious causes for this error are known and no one is at fault when this happens.

In the normal process of fertilization, one sperm fertilizes an egg and the baby forms. The baby will have 46 chromosomes (half from the father and half from the mother). In the case of a molar pregnancy, one scenario is that the sperm fertilizes an empty egg and therefore only a placenta forms (the afterbirth tissues only); this is called a “complete mole.” In another scenario two sperms fertilize one egg and do not form a twin but a placenta and fetus that are abnormal; this is called a “partial mole”. The developing fetus in this case may have too many chromosomes and dies in the uterus. The medical term for this is known as “hydatiform mole”.

In both cases, the pregnancy is abnormal. In the case of the empty egg, the placenta grows in the uterus and makes the pregnancy hormone ( Hcg) that makes a woman feel pregnant but there is not a real pregnancy. Similarly, the Hcg hormone is high in the partial mole and the patient will also feel pregnant and will have the same symptoms that pregnant women complain of but in a more serious manner.

Women with a molar pregnancy may have severe nausea and vomiting, vaginal bleeding, preeclampsia early in pregnancy, high blood pressure, pelvic pain, and enlargement of the uterus that is disproportionate to the gestational age. A molar pregnancy is usually detected with an ultrasound.

A molar pregnancy is most often seen in the oldest and youngest women. The incidence in the U.S. of molar pregnancy is 1 in 1000, but in other geographic locations the incidence is much higher. For example, in southeast Asia the incidence is 8:1000, and women in Mexico and the Philippines have higher rates of molar pregnancies than white or African-American women who have the lowest rate in those populations. History of a previous molar pregnancy predisposes the woman to having another molar pregnancy and the rate increases 10-fold to be 1:100 in this case. The reason for the geographical disparity is not clear but some theories suggest that environmental factors may play a role. Molar pregnancies also could also occur after a miscarriage, a tubal pregnancy, or a normal pregnancy.

When the patient presents for pregnancy care with the above mentioned symptoms, an ultrasound of the uterus may show a lack of a baby and maybe grape-like clusters or other structures that suggest a molar pregnancy. Blood pregnancy tests may show high numbers and there may possibly be elevated liver and thyroid tests.

To treat this, a dilation and curettage (D and C) is performed to evacuate the uterine cavity; this is done very carefully because of the high risk of bleeding. Patients are instructed to avoid pregnancy for one year. Moreover, repeated weekly blood tests are done until the blood pregnancy levels return to normal, and examination of the uterus and the vaginal area is done every two weeks until normal as well. A baseline chest x-ray is also ordered. Effective contraception (pills, a shot or IUD) is recommended because the signs of a repeat pregnancy would be difficult to distinguish from a recurrence of the molar pregnancy and it is very important to distinguish between these possibilities.

A molar pregnancy can recur and can become malignant, spreading to other organs such as the lungs, the liver, and the brain. This form of cancer is treated with chemotherapy, with one injection, or occasionally with more than once agent, depending on the condition.

Normally once a year has passed, women are likely to have a normal pregnancy. So as you can see, Bobbie, your risks are quite small, so when you become pregnant just make sure you get early prenatal care and you should be fine.

Good luck.



Dr. Mona Alqulali is a board certified OB-GYN.