Complications and symptoms

Molar Pregnancy: A rare complication of pregnancy

One pregnancy complication is molar pregnancy. In this article we cover: Can you detect molar pregnancy in ultrasound? What are the 15 symptoms?

Pregnancy is a life-changing event for every woman. As joyful as the entire journey is, there are various complications and doubts throughout the 9 months. During these months, a woman goes through a lot of physical and emotional turmoil. Any complication during pregnancy is not only dangerous for the child, but also for the mother. One such case is a molar pregnancy. In this article we will cover: can you detect molar pregnancy in ultrasound? What are molar pregnancy symptoms.

Usually, there are two types of complications in pregnancy; non-molar and molar.

  1. Non-molar complications include Placental Site Trophoblastic Tumor (PSTT) and choriocarcinoma.
  2. Molar complications includes complete and partial molar pregnancy.[1]

What is Molar Pregnancy?

Molar Pregnancy, also called Hydatidiform Mole or HM, is a very rare complication of pregnancy. A typical hydatidiform mole is a voluminous mass or swollen, sometimes cystically dilated, chorionic villi, appearing grossly as grapelike structures.

In this complication, which is more properly known as Gestational Trophoblastic Disease (GTD), the trophoblast cells (which normally develop in the placenta) grow abnormally.[1]

Unfortunately, this complication leads to the termination of pregnancy because the fetus is unable to form properly. Instead of a healthily forming fetus, there is a lump of cells that grow in the womb. In a normal pregnancy, the fertilized ovum grows into a fetus with clearly defined cell segregation and maturation. In a molar pregnancy, a tumor-like mass resembling a mole or lump of cells is produced. The accumulation of cells that form a mole-like mass – and the failure to properly develop the placenta – leads to an insufficient supply of oxygenated blood and nourishment.[1]

molar pregnancy

Types of Molar Pregnancy

Complete Molar Pregnancy

In a complete mole, there is no fetal part at all. Instead, there is a mole of abnormal cells that grow abnormally in the uterus.[1]

The levels of the Beta Human Chorionic Gonadotropin hormone is extremely elevated.[1]

Moreover, the two types of trophoblasts in the placenta, called syncytiotrophoblast and cytotrophoblast, are equally proliferated. [1]

A complete molar pregnancy occurs in 2% of all pregnant women. [1]

Partial Molar Pregnancy

As compared to complete moral pregnancy, there is the presence of a fetal part in partial molar pregnancy. However, the fetus is abnormal and is unable to survive, thus leading to termination of pregnancy. [1]

The level of Beta Human Chorionic Gonadotropin is elevated, but not as high as in complete molar pregnancy. [1]

The syncytiotrophoblast and cytotrophoblast cells that are present in the placenta undergo partial and complete proliferation. [1]

There is nearly nil occurrence of partial molar pregnancy among pregnant women. [1]

A complete mole is more dangerous than a partial mole because it has the tendency to convert into choriocarcinoma. [1]

This disease has proven to be quite dangerous . It often leads to cancerous conditions which aggravate with time if adequate treatment is not acquired. [1]

Molar Pregnancy in Ultrasound

In ultrasound, high-frequency sound waves are directed towards the abdominal and pelvic region.

Radiology allows ultrasound tests to detect molar pregnancy as early as nine weeks. When the high-frequency sound waves echo, they produce specific patterns upon imaging.

In case of complete molar pregnancy

Ultrasound scans may reveal an intrauterine mass with cystic spaces associated with the absence of fetal content and amniotic fluid. Moreover, there is a thick cystic placenta that fills the uterus, due to which the uterus appears quite enlarged. Crystal-like structures show the presence of ovarian cysts. [2]

Usually, it is difficult to diagnose molar pregnancy by relying on imaging in the first trimester. This is because the results resemble a normal pregnancy or empty gestational sac. Therefore, less than 50% of cases of molar pregnancy are detected in the first trimester. In ultrasound imaging, theca lutein cysts are quite clearly visible. [2]

The characteristic feature of an ultrasound scan is the snowstorm or bunch of grape appearance. [2]

A color Doppler scan reveals high velocity with a low impedance flow. [2]

In case of partial molar pregnancy

Ultrasound scans can reveal growth-restricted fetuses and low amniotic fluid. There is the presence of fetal and placental content; the fetus is well-developed but the growth is retarded. It presents the fetus dead or alive with hydrophobic degeneration. The placenta is quite thick and large in proportion to the uterine cavity due to cystic-like appearance. The cystic spaces in the placenta are not always present.

Moreover, the ultrasound scan reveals a gestational sac or amniotic cavity which may be empty or may contain amorphous small fetal content. It is surrounded by a thick outline of placental echoes which intermixes with cystic spaces.

A color Doppler scan shows high velocity with low impedance flow. [3]

What are the symptoms of Molar Pregnancy? [4]

In the beginning, everything appears normal. As the pregnancy progresses, symptoms begin to appear in the first trimester. These include: 

  • Vaginal bleeding. This varies in color; from dark brown to bright red, the discharge can appear in any shade.
  • There is often a brownish watery discharge instead of proper vaginal bleeding.
  • In a normal pregnancy, there is nausea and vomiting; in molar pregnancy, the intensity of morning sickness worsens. Thus, the intensity of nausea and vomiting increases and can happen at any time during the day.
  • Sudden severe abdominal pain caused by internal bleeding.
  • Grape-like cysts usually discharge through the vagina.
  • Immense pelvic pain or pressure.
  • The height of fundus is extraordinarily large in the first trimester which indicates abnormality.
  • Sometimes the uterine growth varies between too much and too little.
  • High blood pressure.
  • Proteinuria occurs, which is the presence of protein in the urine after 20 weeks of pregnancy. Proteinuria coupled with high blood pressure is called Pre-eclampsia.
  • Ovarian cysts on the ultrasound.
  • Usually, upon running regular CBC, there is a decrease in red blood cells (RBCs). This condition is called anemia.
  • Thyroid gland overworks, causing intense symptoms of hyperthyroidism.
  • Ultrasound shows no fetal movement or heartbeat; a dead or abnormal fetus.
  • βhCG level,

Most of the symptoms are also observed in normal pregnancy and therefore do not bother the soon-to-be-mother. However, some characteristic symptoms indicate abnormality. Ultrasound tests can confirm the condition of molar pregnancy.

What are the causes of Molar Pregnancy?

The occurrence of molar pregnancy is beyond the control of a woman. It does not happen due to intake or any physical or biological action.

The cause lies solely in genetics.

The two types of molar pregnancy have different patterns of gene involvement. To understand how a flaw in gene mixing causes this, it is necessary to understand the normal process.

In human beings, there are 23 pairs of chromosomes. When a sperm fuses with an ovum, one pair – from both male and female, which are XX and XY respectively – combine.

In a molar pregnancy, the ovum is empty. There are no chromosomes in it. When one sperm fuses with the ovum, it undergoes duplication and the resulting chromosomal number becomes 46 XX or 46YY. The initial chromosomal content after fertilization duplicates, producing abnormal genetic products. In this case, the zygote is homozygous diploid. However, when two sperms fuse an empty ovum, it also undergoes duplication forming 46 XX or 46 XY. [1]

In this case, the zygote is heterozygous diploid. [1]

In a partial molar pregnancy, two normal sperms fuse with one normal ovum. The genetic makeup is 69 XXY, 69 XYY, or 69 XXX. This is due to two sets of chromosomes from the father and one set of chromosomes from mother. [1]

As a result, the zygote is triploid. [1]

What are the risk factors? [5]

Although the occurrence is quite rare, in 1 out of 1000 pregnancies, it is necessary to understand the risk factors. For instance, the most common risk factors are:

Maternal age

In pregnancy, the age of the mother is the most critical and important aspect. The risk of developing a molar pregnancy is higher for women who are older than 45. The risk is equally high when the mother is younger than 20. Therefore, it is necessary to keep age in mind when planning a pregnancy.

Thus, pregnancy in teenage and middle age is the most restricted age for pregnancy.

Previous history

All those women who have had a molar pregnancy before are likely to develop it again. Repetition occurs in 1 out of every 100 women. If a woman has had more than one molar pregnancy, then her chances to develop another are around 1 in 5.

Blood group

Women with blood groups A and AB are at a slightly higher risk of developing molar pregnancy.


Among all ethnicities, Asian women are most at risk of developing molar pregnancy. As compared to women of other ethnicities, the risk is twice.

Infertility issues

There are numerous women who have difficulty conceiving. This is due to underlying issues concerned with fertility which have a huge impact on the conception. In conclusion, such women often end up with a molar pregnancy.

How to prevent Molar Pregnancy? [6]

A molar pregnancy can only be prevented if you are familiar with the age group which is at highest risk. It is best not to plan pregnancy in teenagers and during middle age, thus avoiding the chance to develop one.

Moreover, if you have had a molar pregnancy before, it is best to wait for 6 to 12 months before another pregnancy. The risk of developing another is 1 in 80 women.

Other than these two preventions, there is nothing else that can be done. Developing a molar pregnancy is not under a woman’s control.

Due to the interference of non-modifiable and uncontrollable factors, a molar pregnancy can’t be prevented.

How is it treated? [7]

It is necessary to understand that such a pregnancy cannot continue since the problem lies at the genetic level. There are some treatment options that must be employed to prevent any fatal complications.

Dilation and Curettage (D&C)

In this technique, shortened as D&C, the abnormal molar tissue is removed from the uterus.

This treatment plan is conducted under the effect of anesthesia. A doctor inserts a speculum into the vagina of a woman to observe the cervix. Next, the doctor dilates the cervix. With the help of a vacuum, the device removes the molar tissue from the uterus.

HCG monitoring

The removal of molar tissue from the uterus does not allow the woman’s body to plan pregnancy again. There is a slight possibility that a small part of molar tissue is still present in the uterus; that tissue basically produces the HCG hormone. A doctor measures the HCG level until it drops to normal. If the level of HCG fails to become normal, then there is a need for additional treatment.

For 6 to 12 months, the HCG levels are continuously under observation.


A molar pregnancy can convert into Gestational Trophoblastic Neoplasia (GTN). In case of GTN or no desire for future pregnancies, it is better to remove the uterus.


  1.   Kumar, V., Abbas, A. K., & Aster, J. C. (2018). Chapter 19: Female Genital System and Breast. In Robbins Basic Pathology (10th ed.). Pennsylvania: Elsevier.
  2.   Radswiki. (n.d.). Complete hydatidiform mole: Radiology Reference Article. Retrieved June 26, 2020, from
  3.   Radswiki. (n.d.). Complete hydatidiform mole: Radiology Reference Article. Retrieved June 26, 2020, from
  4.   Molar pregnancy. (2017, December 14). Retrieved June 26, 2020, from
  5.   Gestational Trophoblastic Disease – Risk Factors. (2019, August 01). Retrieved June 26, 2020, from
  6.   Molar Pregnancy Prevention. (n.d.). Retrieved June 26, 2020, from
  7.   Molar pregnancy. (2017, December 14). Retrieved June 26, 2020, from

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