A normal pregnancy occurs when a sperm meets an egg resulting in fertilisation which ultimately develops into an embryo. But in the case of a molar pregnancy, which occurs in one of every 1,500 pregnancies, Dr Keisha Buchanan – obstetrician-gynaecologist at ICON Medical Centre — says the fertilised egg grows into what is termed “a mole”.
“A molar pregnancy is an abnormal form of pregnancy that occurs when the sperm or egg has abnormal genetic material. Molar pregnancies are a form of Gestational Trophoblastic Disease (GTD) in which abnormal pregnancy tissue develops, and while some forms of GTD can develop into cancer, molar pregnancies are non-cancerous,” she explained.
There are two types of molar pregnancies: complete and partial.
“In the case of complete molar pregnancies, the sperm fertilises an egg that does not have genetic material. A normal foetus does not develop but a lot of abnormal tissue grows in the womb that looks like a cluster of grapes or cystic material on ultrasound,” Dr Buchanan continued.
However, in the case of a partial molar pregnancy, Dr Buchanan says that two sperm fertilise one egg. The foetus may be very defective and the placenta is the site of the molar growth. In the complete mole, no foetal tissues develop but excessive placental tissues do.
The doctor further explained that while a molar pregnancy can occur in a woman of any age, the risk increases with age — it is common in women more than 35 years old. Other women at risk of molar pregnancies are those who have had a prior molar pregnancy, those who have had two or more miscarriages, or when there are low levels of folic acid and Carotene (Vitamin A) in the body.
“Molar pregnancies present with similar symptoms as a normal pregnancy such as a missed period; however, vaginal bleeding is more likely to happen, as well as other symptoms such as nausea and vomiting, sore breasts, fatigue and poor appetite.”
While most of these symptoms are similar to those of a normal pregnancy, Dr Buchanan explained that vaginal bleeding may reveal tissue that looks like grapes due to its cystic appearance. Nausea and vomiting are more likely to be severe, and often advance to Hyperemesis Gravidarum in which there is excessive nausea and vomiting which results in weight loss, electrolyte derangements and may require hospitalisation.
Other characteristics common in these pregnancies include the possibility of high blood pressure developing in the first trimester, and symptoms of an overactive thyroid may be present, such as anxiety, palpitations and weight loss. Also, since with molar pregnancies the foetus is genetically defective, it may exhibit signs of growth restriction, abnormalities in the organs, intrauterine death may occur, and the growth of the uterus may be more rapid than in normal pregnancies.
Fortunately, with the availability of high-resolution ultrasound, Dr Buchanan said that molar pregnancies can be detected as early as the first trimester.
“Blood tests to check for the pregnancy hormones Beta Human Chorionic Gonadotrophin (Serum BHCG) can be done. A partial mole is marked by an abnormal-appearing foetus, and placental tissue that appears cystic on ultrasound. On the other hand, a complete mole would appear as placental tissue that looks cystic without any apparent foetus,” Dr Buchanan advised.
She added that some women may be diagnosed after they miscarry and tests are done on the tissue passed from the vagina.
After diagnosis, Dr Buchanan said that the general course of treatment usually starts with a surgical procedure called a suction curettage, which involves removal of the abnormal tissue for further testing. In addition to this, the pregnancy hormone Serum BHCG has to be monitored for up to a year to confirm that no residual abnormal tissue remains or regrows. When the serum reaches zero, this usually confirms that the molar pregnancy has resolved. However, if the hormone does not fall or if it starts to rise rapidly, this could be a sign of an invasive mole or a cancerous transformation in the disease called Choriocarcinomas. This, she said, is aggressive cancer that can rapidly spread, but it has an excellent prognosis as it responds well to chemotherapy such as Methotrexate.
Dr Buchanan said that the possibility of an invasive mole or Choriocarcinoma developing also increases if a woman becomes pregnant within a year of having a molar pregnancy. In general, however, the chances of it recurring are quite slim.
“After a molar pregnancy is treated and resolves, the woman's fertility is not affected by this condition. Also, if the rare cancerous transformation — Choriocarcinoma — develops, up to 90 per cent of women will still have the ability to get pregnant after the cancer is treated. As such I generally recommend that these women use highly effective contraceptives such as an implant or an injectable method,” Dr Buchanan advised.