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Getting pregnant after a molar pregnancy
Molar pregnancy is a pregnancy abnormality that affects the placenta in particular and whose cause occurs at the time of fertilization. Both the placenta and the embryo develop abnormally due to abnormalities of the egg and sperm. There are two possibilities of molar pregnancies. One is called complete, the other is called partial. The outcome of a molar pregnancy is in both cases necessarily negative because the genetic material is incomplete. Let us therefore take a closer look at what these two types of abnormal pregnancies consist of and whether it is possible to become pregnant afterwards.
What is a molar pregnancy?
A complete molar pregnancy, also known as a complete hydatidiform mole, is commonly the result of fertilisation between two sperm cells that have two sets of chromosomes, known as diploid, and an egg cell without a nucleus, known as anucleate. An egg cell without a nucleus is devoid of genetic material. The embryo is therefore non-existent. Only the placenta develops and will grow in the form of grape bunches with numerous cysts, which can only be detected by an ultrasound. Therefore, a molar pregnancy is a pregnancy without an embryo; this pregnancy does not result in the birth of a child.
Partial molar pregnancy with an embryo, also called a partial hydatidiform mole, is the result of incomplete fertilisation between an egg cell with a nucleus and at least one diploid sperm cell. In this type of pregnancy, there is an embryo, but it is not viable because the fertilised egg has chromosomal abnormalities. The placenta also acts abnormally, as in the case of a complete mole.
In both cases, the pregnancy cannot be carried to term because even when there is an embryo, it is not viable.
Symptoms of molar pregnancy
There are two main symptoms of a molar pregnancy.
First, the signs of pregnancy may become more pronounced, and the volume of the uterus may simultaneously increase.
Second, heavy bleeding and anaemia may occur. In this case, a pelvic endovaginal ultrasound should be performed to determine whether the pregnancy is molar.
A rapid or spontaneous miscarriage, although rare, can also be a sign of a molar pregnancy. It is the analysis of the miscarriage that will determine whether it is a hydatidiform mole. A miscarriage is not necessarily the result of a hydatidiform mole.
If there are no alarming symptoms, only an ultrasound will reveal whether the pregnancy is abnormal or not.
How is it managed?
A partial or complete hydatidiform mole is non-viable in most cases and can be dangerous to the health of the pregnant woman. Even when the correct number of chromosomes are present, they contribute a genetic abnormality. There is, therefore, a low chance of survival for the embryo. It is thus necessary to remove the abnormal placenta and the embryo, if present, and to perform a uterine aspiration.
After the operation, anatomopathology is usually performed to determine the type of mole.
It is necessary to perform an ultrasound in the two weeks following the uterine aspiration to determine that there is no retention and no complications. If there is retention, a second aspiration must be performed.
In France, a practitioner can propose that the patient be referred to the Trophoblastic Disease Centre in Lyon to accompany and monitor these types of pregnancies.
What are the risk factors?
The only risk of complication in a molar pregnancy is a gestational trophoblastic tumour. When the HCG level increases or stagnates, there is a risk of a gestational trophoblastic tumour. This occurs in approximately 15% of total molar pregnancies and few partial molar pregnancies with embryos.
This is because the molar tissue becomes a tumour. The tumour may then invade nearby organs, particularly the uterus. This describes an invasive mole or choriocarcinoma. Depending on the results and the type of tumour, chemotherapy may be necessary.
Is it possible to become pregnant after a molar pregnancy?
It is possible to become pregnant after a molar pregnancy provided that the treatment and monitoring are appropriate. The risk of a second molar pregnancy is low, but there is a 0.5 to 1% chance of recurrence.
The HCG level should therefore be monitored once a month for six months in case of a complete mole. Thereafter, monitoring is considered complete. This monitoring is essential to avoid the recurrence of a mole in a subsequent pregnancy.
In the case of a partial mole, a blood test should be carried out for three weeks. If these markers levels are negative, monitoring is considered complete.
If there is a trophoblastic tumour, there are two types of monitoring. In the case of monochemotherapy, monthly blood tests are taken for 12 months. In the case of polychemotherapy, monthly blood tests are taken for 18 months.
In most cases, chemotherapy treatments do not affect fertility. It is, therefore, possible to become pregnant after these monitoring periods.
Getting pregnant after a molar pregnancy: should precautions be taken?
An HCG test should be taken three months after giving birth (or after a terminated pregnancy) with a molar pregnancy.
A molar pregnancy, especially if accompanied by a tumour, can be stressful and discouraging. Terminating a pregnancy is difficult, whether voluntarily or not. However, a molar pregnancy has no negative impact on future pregnancies and the health of the pregnant woman. While it is imperative to have regular and serious monitoring, it is possible to become pregnant after the monitoring periods.