What is a molar pregnancy?A molar pregnancy happens when tissue that normally becomes a fetus instead becomes an abnormal growth in your uterus. Even though it isn’t an embryo, this growth triggers symptoms of pregnancy. A molar pregnancy should be treated right away. This will make sure that all of the tissue is removed. This tissue can cause serious problems in some women. About 1 out of 1,500 women with early pregnancy symptoms has a molar pregnancy. This means that 1,499 women out of 1,500 don’t have this problem.
What causes a molar pregnancy?Molar pregnancy is thought to be caused by a problem with the genetic information of an egg or sperm. There are two types of molar pregnancy: complete and partial.Complete molar pregnancy. An egg with no genetic information is fertilized by a sperm. The sperm grows on its own, but it can only become a lump of tissue. It cannot become a fetus. As this tissue grows, it looks a bit like a cluster of grapes. This cluster of tissue can fill the uterus.Partial molar pregnancy. An egg is fertilized by two sperm. The placenta becomes the molar growth. Any fetal tissue that forms is likely to have severe defects.Sometimes a pregnancy that seems to be twins is found to be one fetus and one molar pregnancy. But this is very rare. Things that may increase your risk of having a molar pregnancy include:1.Age. The risk for complete molar pregnancy steadily increases after age 35.2.A history of molar pregnancy, especially if you’ve had two or more.3.A history of miscarriage.4.A diet low in carotene. Carotene is a form of vitamin A. Women who don’t get enough of this vitamin have a higher rate of complete molar pregnancy.
What are the symptoms?A molar pregnancy causes the same early symptoms that a normal pregnancy does, such as a missed period or morning sickness. But a molar pregnancy usually causes other symptoms too. These may include:
- Bleeding from the vagina.
- A uterus that is larger than normal.
- Severe nausea and vomiting.
- Signs of hyperthyroidism. These include feeling nervous or tired, having a fast or irregular heartbeat, and sweating a lot.
- An uncomfortable feeling in the pelvis.
- Vaginal discharge of tissue that is shaped like grapes. This is usually a sign of molar pregnancy.
Most of these symptoms can also occur with a normal pregnancy, a multiple pregnancy, or a miscarriage.How is a molar pregnancy diagnosed?Your doctor can confirm a molar pregnancy with:
- A pelvic exam.
- A blood test to measure your pregnancy hormones.
- A pelvic ultrasound.
Your doctor can also find a molar pregnancy during a routine ultrasound in early pregnancy. Partial molar pregnancies are often found when a woman is treated for an incomplete miscarriage.
Natural history.An hydatidiform mole is a pregnancy/conceptus in which the placenta contains grapelike vesicles (small sacs) that are usually visible with the naked eye. The vesicles arise by distention of the chorionic villi by fluid. When inspected in the microscope, hyperplasia of the trophoblastic tissue is noted. If left untreated, a hydatidiform mole will almost always end as a spontaneous abortion (miscarriage). Based on morphology, hydatidiform moles can be divided into two types: in complete moles, all the chorionic villi are vesicular, and no sign of embryonic or fetal development is present. In partial moles some villi are vesicular, whereas others appear more normal, and embryonic/fetal development may be seen but the fetus is always malformed and is never viable.In rare cases a hydatidiform mole co-exists in the uterus with a normal, viable fetus. These cases are due to twinning. The uterus contains two conceptuses: one with an abnormal placenta and no viable fetus (the mole), and one with a normal placenta and a viable fetus. Under careful surveillance it is often possible for the woman to give birth to the normal child and to be cured of the mole. The etiology of this condition is not completely understood. Potential risk factors may include defects in the egg, abnormalities within the uterus, or nutritional deficiencies. Women under 20 or over 40 years of age have a higher risk. Other risk factors include diets low in protein, folic acid, and carotene. The diploid set of sperm-only DNA means that all chromosomes have sperm-patterned methylation suppression of genes. This leads to overgrowth of the syncytiotrophoblast whereas dual egg-patterned methylation leads to a devotion of resources to the embryo, with an underdeveloped syncytiotrophoblast. This is considered to be the result of evolutionary competition with male genes driving for high investment into the fetus versus female genes driving for resource restriction to maximise the number of children.