Molar pregnancy occurs in around 1 in 1,000 pregnancies. And while they are rare, molar pregnancies can happen to anyone, and there is nothing you can do to avoid them, so you should try not to blame yourself if it happens to you.
Some of the symptoms of molar pregnancy are easily confused with other, intense pregnancy symptoms. To help you understand the difference, we spoke to Dr. Gian Carlo Di Renzo, chair of the department of obstetrics and gynecology, University of Perugia, Italy. With his help, we explain what a molar pregnancy is, what the signs are, and what to do if you experience one.
What is a molar pregnancy?
A molar pregnancy — known more scientifically as a “hydatidiform mole” — is when fertilization doesn’t quite work the way it’s supposed to. This condition causes tissue to grow in the uterus that you wouldn’t usually find there, called “trophoblastic tissue.” If left untreated, these growths can cause health problems.
In a healthy pregnancy, a sperm fertilizes an egg. Each brings 23 chromosomes, containing all sorts of genetic material that determines lots of factors, from the color of our hair to the sound of our voice. But in a molar pregnancy, there’s an error in the process, which results in an imbalance of these chromosomes. There are two types of molar pregnancy: complete and partial.
Complete molar pregnancy
“A complete mole is when there is an egg with chromosomes that don’t work or an egg without any chromosomes in it — it’s empty,” Dr. Di Renzo says. That means that when it’s fertilized (either by one sperm or sometimes two at the same time), it contains only the sperm’s chromosomes. As a healthy pregnancy needs chromosomes from both the sperm and egg, a fetus can’t be created in this situation. But the tissue that forms the placenta still grows because your body still thinks it’s pregnant. The excess tissue can also continue to grow, developing into a noncancerous tumor in the uterus.
A complete mole is considered riskier for your health than a partial mole, “because it grows very quickly,” Dr. Di Renzo says. It also means that your pregnancy symptoms would advance more quickly than expected. “At eight weeks, you might feel as pregnant as you would at 16 weeks, because your uterus is growing so fast. Sometimes, you can think you have twins or multiple pregnancies because of the rate of the growth, but the ultrasound will show there is no fetus,” he explains.
Partial molar pregnancy
A partial molar pregnancy is slightly more complex. This is when the egg’s chromosomes are there, but two sperm fertilize an egg at the same time, so there are two sets of chromosomes from the sperm. This scenario can lead to early signs of a fetus, but unfortunately, it can’t develop into a healthy baby.
“A partial molar pregnancy isn’t quite as dangerous as a complete mole, but it can go unnoticed for longer,” Dr. Di Renzo says. This is because a person might bleed, which is a symptom of molar pregnancy (more on that below), and assume they have had a miscarriage. Based on this assumption, they might not go to their health care provider for tests, meaning the remaining molar tissue in the uterus isn’t discovered as quickly.
Learning that your pregnancy is molar and won’t result in a baby can be understandably hard, especially as you will likely have experienced many of the usual symptoms of a healthy pregnancy and may not have been aware there was anything wrong. Scroll down for advice on how to cope if you find yourself in this difficult situation.