What is a molar pregnancy?

Molar pregnancy, sometimes known as a hydatidiform mole, is a subset of gestational trophoblastic diseases (GTD). Molar pregnancy is a rare complication in pregnancy whereby fertilisation of the egg by the sperm goes wrong.¹ This leads to a growth of abnormal cells or clusters of water filled sacs within the uterus. It prevents the development of the placenta and foetus, normally resulting in a miscarriage or if not the pregnancy is terminated by surgery.

There can be complete or partial molar pregnancies. A complete molar pregnancy occurs when a sperm fertilises an egg that contains no DNA from the female. This means no foetal tissue begins to form and the molar tissue will need to be removed by surgery or drug treatment. A partial molar pregnancy forms when two sperm attempt to fertilise the egg at the same time so there is twice as much male DNA then female. Some foetal tissue may develop however a foetus is unable to form leading to a miscarriage. If in either type any molar tissue remains it can form an invasive mole or persistent trophoblastic disease (PTD), which is malignant (cancerous) so normally requires chemotherapy to treat. 

Epidemiology in older women

In the UK between 2000 and 2009 the incidence of molar pregnancies was every 1 in 607 conceptions. For women aged 45 and older the incidence was every 1 in 8 pregnancies.²

An advanced maternal age of women (>40) doubles the chance of complete molar pregnancy however age is not thought to affect the incidence of a partial mole pregnancy.³ The increase in complete molar pregnancy is due to an increase in chromosomal abnormalities with age which decreases the quality of the oocyte (unfertilised immature egg).⁴ It is also important to note the Asian population in the UK are twice as likely to experience a molar pregnancies than the non-Asian population.⁵

Clinical presentation in older women

The presentation of a molar pregnancy can be similar to a regular pregnancy, but the most common symptoms include:

• Vaginal bleeding - this is the most common symptom but unlike bleeding during normal pregnancy it is likely to pass blood clots, or have brown vaginal discharge.
• Grape like cysts that pass out from the vagina
• Severe nausea and vomiting
• Pelvic pressure or pain
• Abdominal swelling - in complete molar pregnancy women tend to have a larger tummy than expected for the stage of pregnancy. In partial molar pregnancy the abdomen might be smaller than expected.
• Anaemia 
• Pre eclampsia - high blood pressure and protein in the urine is normally found within the last 3 months of pregnancy. If it occurs earlier ,it may indicate a molar pregnancy.

Older women may experience symptoms that overlap with age related gynaecological issues such as menopause. For example abnormal vaginal bleeding could be mistaken for menopausal symptoms, and vomiting attributed to gastrointestinal issues. This is why you should see a doctor if you experience these symptoms for an accurate diagnosis. 

Diagnosis 

Ultrasound

If a healthcare provider suspects a molar pregnancy they are first likely to carry out an ultrasound. At 8/9 weeks an ultrasound of a complete mole pregnancy might show:

• No embryo or foetus 
• No amniotic fluid
• A large cystic placenta filling the uterus 
• Grape like cysts 

An ultrasound of a partial mole pregnancy might show:

• A foetus that's smaller than expected for the stage of the pregnancy
• Low amniotic fluid
• Unusual placenta

Although an ultrasound is a good diagnostic tool, in some cases it is difficult to distinguish molar pregnancy from other conditions such as missed abortions or retained products of conception.⁶ This issue is also more prevalent in older women who are more likely to experience different complications in conception and during pregnancy.

Blood tests 

Blood tests are considered as a hallmark of a molar pregnancy which shows elevated levels of human chorionic gonadotropin (hCG). hCG is a hormone released by cells in the placenta during pregnancy. In complete mole pregnancies hCG is significantly higher than in a standard or partial pregnancy. For this reason blood tests are not able to accurately detect partial molar pregnancy so should not be used in isolation.⁷ 

Histopathology

Histopathological (microscopic examination of tissue sample) diagnosis can be useful for a definitive diagnosis. It involves the extraction of tissue from the uterus and examination of it.  Histopathology also allows partial and complete molar pregnancy to be distinguished, since foetal tissue can be observed in a partial molar pregnancy. Furthermore histopathology can identify if it's an invasive mole, and therefore require further treatment.⁸

Treatment in older women

A molar pregnancy must be removed or terminated to prevent further health complications . Treatment for molar pregnancy consists of one or more of the following options:

• Dilation and curettage evacuation (D and C)
• Hysterectomy
• hCG treatment

Dilation and curettage evacuation (D and C) 

An instrument called a curette is used to scrape away molar tissue from the uterus. This is a safe procedure but carries slightly more risk in older women, due to an increased chance of complications within this demographic. 

Hysterectomy

Hysterectomy (removal of uterus) is rarely used only if there is an increased risk of gestational trophoblastic neoplasia (GTN) (a subset of GTD that are all malignant) and there is no desire for future pregnancies. Older women may be more likely to opt for hysterectomy since there could be decreased desire for future pregnancy and increased risk of fibroids and endometrial hyperplasia.⁸  Furthermore hysterectomy can prevent PTD and is the only definitive treatment. 

hCG treatment 

After the molar tissue has been removed the hCG levels will be monitored by your provider until the levels decline to normal. Once hCG declines to an undetectable level and remains for 6 months it then indicates full remission.⁹ If hCG remains elevated this indicates persistent GTN. As hCG increases with pregnancy a physician may recommend waiting 6 to 12 months before trying for a baby again. 

Complications in older women

In complete mole pregnancy the risk of developing persistent GTN is higher unlike in partial mole pregnancy. In post molar pregnancy there is a 33% higher chance of GTN developing in women of an advanced maternal age than the general population.¹⁰ This is dangerous as it can metastasise (cancer cells break off from primary site) and travel to other organs having serious health consequences. Additionally the chance of recurrent molar pregnancy is higher in older women,⁸ with a second molar pregnancy common approximately 2-4 years after the first.¹¹ 

Psychological and social implications for older women

The emotional impact of a molar pregnancy should not be understated and is understandably a profound experience of grief, loss and anxiety. Older women in particular may face unique psychological challenges as this may be a final attempt at bearing a child. These emotions can be exacerbated by societal expectations and personal hopes involving motherhood. In addition to a personal support system around you, counselling services can be offered to support women, and provide different coping strategies. Support groups can also be useful to meet individuals who have experienced similar experiences. 

Summary 

• Molar pregnancy in older women presents unique challenges and considerations.
• There are higher incident rates of complete molar pregnancy in older women.
• It can be diagnosed by ultrasound, blood tests, however histopathology is the only definitive way to diagnose.
• In women of an advanced maternal age there may be specific clinical presentation and treatment needs.
• There is also an additional risk of complications such as GTN in older women post molar pregnancy.
• It is also important to take care of psychological and social needs after a molar pregnancy.