Molar pregnancy

A molar pregnancy is an uncommon fault that happens at the very start of a pregnancy. Instead of an embryo and a normal placenta, the womb fills with tissue made up of many small fluid-filled sacs that looks rather like a bunch of grapes. The pregnancy test is positive and the usual signs of pregnancy are there, sometimes more strongly than usual, but a pregnancy like this cannot continue: either there is no baby at all, or the baby cannot survive. It happens in roughly one pregnancy in six hundred to a thousand. The tissue is removed, and afterwards the woman is followed for a while with blood tests, because in a proportion of cases those cells do not simply disappear. The other name for it is a hydatidiform mole, and doctors group it under gestational trophoblastic disease.

What is actually growing in the womb

The sacs that make up a mole are swollen villi — the tiny fronds that should have become the placenta. They fill with fluid and multiply because something went wrong with the chromosomes at conception. There are two forms, and they behave differently.

• Complete mole. A sperm fertilises an egg that has lost its own nucleus, so all the genetic material comes from the father. No embryo forms at all — the womb contains only the abnormal tissue.
• Partial mole. Two sperm fertilise the same egg, leaving one and a half times the normal number of chromosomes. A rudimentary baby may be visible on the scan, but it cannot develop any further.

The distinction is not academic. After a complete mole, the chance that active cells remain and treatment is needed is considerably higher — around one woman in seven, against one in a hundred or two hundred after a partial mole. That is why follow-up after removal is needed in both cases, though it does not last the same length of time.

The signs that give it away

Most often a mole is not picked up from symptoms at all but at the first scan, usually somewhere between eight and fourteen weeks. Until then some women notice nothing whatsoever.

Where there are symptoms, the commonest is vaginal bleeding: anything from brown staining on underwear to obvious bleeding, often stopping and starting again over several days. Sometimes small translucent sacs like grape skins come away with the blood, and that is almost always a mole.

The rest is less obvious. Sickness and vomiting can be far worse than pregnancy sickness usually is: nothing stays down, not even water, and weight starts to fall. The abdomen may look bigger than the dates suggest, because what is growing is the molar tissue rather than a baby. Occasionally there are signs that have no business appearing so early — a racing heart, trembling hands, sweating and inability to tolerate heat (the pregnancy hormone in high concentrations drives the thyroid), or raised blood pressure with swelling before twenty weeks.

There is one further situation: the pregnancy ends looking like an ordinary miscarriage, and the mole comes to light later, when the tissue that came away is examined.

When it cannot wait

Call an ambulance (in Spain, Italy, Portugal, Poland and Ukraine the single European number is 112) if a pregnant woman has:

• heavy bleeding — a pad soaked through in an hour or less, with large clots;
• sudden weakness, pallor, cold sweat or fainting;
• sudden breathlessness, chest pain or coughing up blood;
• a severe headache with disturbed vision, vomiting and high blood pressure before twenty weeks;
• a fast heartbeat with trembling, fever and agitation;
• a temperature above 38 degrees with lower abdominal pain and offensive discharge.

Breathlessness and chest pain in a molar pregnancy are not nerves: fragments of the overgrown tissue can reach the blood vessels of the lungs. A headache with high pressure and swelling this early is also almost unheard of in a normal pregnancy, yet it does happen with a mole. In every other case — light staining, worsening sickness, a bump that seems large for the dates — an ambulance is not what is needed, but a doctor should see you the same day rather than at the next booked appointment.

How the diagnosis is made

The first test is an ultrasound scan, usually done through the vagina: in early pregnancy a small internal probe gives a far clearer picture than scanning through the abdomen. With a complete mole the womb is filled with small sacs of a characteristic appearance and there is no baby. A partial mole is harder to see and, early on, is easily mistaken for a missed miscarriage or an ordinary one.

The second test is a blood test for chorionic gonadotrophin, the pregnancy hormone. In a molar pregnancy it is usually well above what the dates would predict. A high figure on its own proves nothing — twins do the same — but taken together with the scan it tips the balance.

The definitive answer comes only from examining the tissue itself under the microscope after it has been removed: that is what separates a complete mole from a partial one and from an ordinary miscarriage. This is why tissue passed or removed in any early pregnancy loss is sent to the laboratory. It is worth not treating that step as a formality, because everything that follows rests on the result. Thyroid, liver and kidney function are checked as well, and with very high hormone levels a chest X-ray may be arranged.

How the mole is removed

The usual method is suction removal: the contents of the womb are drawn out through a fine tube, under general anaesthetic or deep sedation, and it takes only minutes. Scraping with a sharp instrument is avoided where possible. Drugs that make the womb contract are used sparingly and only on a specialist's decision, because with a complete mole they raise the chance that chemotherapy will be needed afterwards.

Sometimes the mole comes away on its own, like a miscarriage. Even then the doctor needs to know, and the tissue should be kept for examination — without it the diagnosis stays a supposition.

Women who are rhesus negative are given anti-D immunoglobulin in certain circumstances; ask the doctor looking after you. For a few days after the procedure there is some bleeding and dragging pain low in the abdomen, and that is expected. Bleeding that gets heavier, a fever, or discharge that smells unpleasant are not expected, and the clinic should be contacted straight away.

Follow-up: what the blood tests are for

Once the mole has been removed, the point is to be sure that no active cells are left behind, and the only way to see that is to track the pregnancy hormone. At first the tests are frequent, every week or two; once the level reaches normal they are spaced out and carry on for several more months. How long the whole thing lasts depends on the type of mole and on how quickly the hormone fell — the team following you up will give the exact schedule.

Throughout that period pregnancy has to be avoided, and this is not a rule for its own sake. A new pregnancy pushes the hormone up by itself, which would make it impossible to tell apart from the disease coming back, and the follow-up would have to start again from the beginning. So contraception is needed from day one and is best chosen with a doctor: a coil is not usually fitted until the level has come down to normal. Sex can be resumed once the bleeding has stopped and you feel ready.

If the hormone does not fall

Sometimes some of the cells stay in the womb and keep growing. The hormone level then plateaus or climbs again and the bleeding returns. This is called persistent trophoblastic disease; its rarer and more aggressive form, which can spread to the lungs and elsewhere, is choriocarcinoma.

It sounds alarming, and yet this is precisely a case where the outlook is far better than the name suggests: the disease responds extremely well to chemotherapy and is cured in more than ninety-eight women out of a hundred. One drug and a few cycles are usually enough, the womb does not have to be removed, and fertility is preserved. After treatment, waiting about a year before trying for a baby is advised.

This is exactly what those tedious repeated blood tests are for: they catch a relapse long before it has a chance to announce itself.

The next pregnancy, and how it feels

A molar pregnancy has almost no effect on the ability to conceive. The chance of it happening again is small — roughly one or two in a hundred; after two moles in a row it is higher, and the couple are then offered genetic counselling. In the next pregnancy you will be asked to come for a scan earlier than usual, at around seven or eight weeks, and a few weeks after the birth or the end of that pregnancy the hormone is checked once more.

The emotional side deserves saying out loud. This is the loss of a pregnancy, and grieving afterwards is normal even if it was only a few weeks along. What makes it harder is that ordinary grief comes bundled with uncertainty: months of going for blood tests, putting off the next attempt, hearing the word tumour and living in limbo. Partners feel it too, they are simply more likely to keep quiet about it. If after several weeks things are no easier, if sleep and appetite have gone, if the anxiety will not let up or the thought appears that there is no point carrying on, that is a reason to see a psychologist or therapist — not a sign of weakness.

Online consultation

Talking to a doctor remotely helps in two situations. The first is when something is happening right now and it is not clear how urgent it is: from a description of the bleeding, the pain and the dates, a doctor will say whether to go in immediately, arrange a scan today, or wait calmly for the booked appointment. The second is once the diagnosis has been made and the paperwork is in front of you: going through the scan and laboratory reports, understanding the difference between a complete and a partial mole, what the hormone figures mean as they change, and why follow-up has been set for that particular length of time.

Later on the questions change: which contraception to use during follow-up, when it is safe to plan a pregnancy, what to do if the level has stopped falling, how to prepare for the next pregnancy. The limits of the format are obvious — examining you, scanning you and taking blood cannot be done through a screen, and heavy bleeding, fainting or sudden breathlessness call for an ambulance rather than a phone call.

This material is for information only and does not replace medical advice.