Molar Pregnancy
Molar pregnancy or a hydatidiform mole is a condition in which a defective zygote develops into a mass of cysts instead of an embryo and placenta. This belongs to a class of diseases called gestational trophoblastic diseases which include invasive mole and a choriocarcinoma.
A normal human zygote contains 23 pairs of chromosomes with half derived paternally and the other half maternally. In a complete mole the chromosomes of the mother are inactivated or lost and the father’s chromosome duplicates itself. In a partial mole the mother’s chromosomes are present however there is usually a second copy of the father’s chromosomes as well, so instead of 46 chromosomes, 69 are present.
Grossly in a complete mole there is no embryo and the entire uterus is filled
with cysts developed from the abnormal placenta. A partial mole may have a developing embryo, but it is always deformed and cannot survive. A molar pregnancy is always abnormal and can never survive.
The initial symptoms of of molar pregnancy are very similar to that of pregnancy. But the nausea and vomiting tend be particularly severe. Other than these women may experience dark brown to reddish bleeding during the first trimester. Some women may also notice passage of grape like cysts through the vagina. In rare cases women may feel pain in the pelvis. Another important and consistent feature of molar pregnancy is uterine size disproportionate to gestational age. In a molar pregnancy the uterine size is always disproportionately greater.
Although the causes of molar pregnancy are not completely known, there are some factors which may influence its incidence:
- Maternal age over 35 and less than 20 years is associated with a higher incidence of molar pregnancy
- Previous molar pregnancy can lead to repeat molar pregnancy
- Some ethnic groups like south East Asians.
The following conditions are associated with molar pregnancy :
- Preeclampsia
- Hyperthyroidism
- Anemia
- Ovarian cysts
Diagnosis of molar pregnancy is done by a combination of blood tests and ultrasound. The blood levels of a hormone produced by the placenta are measured. This hormone HCG is secreted both during normal pregnancy and molar pregnancy; however its levels in molar pregnancy are far higher than in a normal pregnancy.
Ultrasound is the most definitive diagnostic method for molar pregnancy. The typical appearance of a H mole on ultrasound is described as “snow storm appearance”. The following are the features of a complete and partial mole on ultra sound:
An ultrasound of a complete molar pregnancy may show:
- No embryo or fetus
- No amniotic fluid
- A thick cystic placenta nearly filling the uterus
- Ovarian cysts
An ultrasound of a partial molar pregnancy may show:
- A growth-restricted fetus
- Low amniotic fluid
- A thick cystic placenta
Once molar pregnancy is diagnosed the treatment of it is surgical removal of the mole by D&C. D&C stand dilatation and curettage. This procedure is generally carried out under sedation or mild general anaesthesia on an OPD basis.
Once the mole has been removed it is important to regularly follow up with serial measurements of HCG to document complete removal of the mole. A follow up of one year is recommended by most doctors. Since pregnancy will interfere with monitoring of HCG it is recommended to put of pregnancy for at least one year following a molar pregnancy.
In some rare cases the molar pregnancy may invade into the muscular structure of uterus thus causing bleeding. It is difficult to remove and is generally treated with chemotherapy. In women who do not desire further fertility it can be completely cured by removal of the uterus (Hysterectomy).
A molar pregnancy in very rare circumstances may lead to a cancer known as choriocarcinoma. Choriocarcinoma is a very rapidly growing cancer, but is successfully treated with chemotherapy.
Losing a pregnancy can often be devastating especially when you know that it can impact your future pregnancies as well. But it is pertinent and positive to recollect that many women who have had molar pregnancy have gone on to have successful pregnancies later on in life. You can seek the help of women who have had molar pregnancy or support groups to help you cope up with the loss.