[citation needed] GTD can simulate pregnancy, because the uterus may contain fetal tissue, albeit abnormal.

This tissue may grow at the same rate as a normal pregnancy, and produces chorionic gonadotropin, a hormone which is measured to monitor fetal well-being.

All five tumours arise from trophoblast cells that form the outer layer of the blastocyst in the early development of the fetus.

In a normal pregnancy, trophoblasts aid the implantation of the fertilised egg into the uterine wall.

Conception takes place, but placental tissue grows very fast, rather than supporting the growth of a fetus.

[15] Vaginal bleeding, enlarged uterus, pelvic pain or discomfort, and vomiting too much (hyperemesis) are the most common symptoms of GTD.

But GTD also leads to elevated serum hCG (human chorionic gonadotropin hormone).

[16] The initial clinical diagnosis of GTD should be confirmed histologically, which can be done after the evacuation of pregnancy (see Treatment below) in women with hydatidiform mole.

Women with persistent abnormal vaginal bleeding after any pregnancy, and women developing acute respiratory or neurological symptoms after any pregnancy, should also undergo hCG testing, because these may be signs of a hitherto undiagnosed GTD.

[18] Both are composed of intermediate trophoblast, but their morphological features and clinical presentation can differ significantly.

Placental site nodules are lesions of chorionic type intermediate trophoblast, usually small.

[26][27][28][29] In women with low risk gestational trophoblastic neoplasia, a review has found that Actinomycin D is probably more effective as a treatment and more likely to achieve a cure in the first instance than methotrexate.

[30] Only a few women with GTD have poor prognosis metastatic gestational trophoblastic disease.

It has been estimated by the Royal College of Obstetricians and Gynaecologists that the age at menopause for women who receive single agent chemotherapy is advanced by one year, and by three years for women who receive multi agent chemotherapy.

[32][33] The use of a reliable contraception method is very important during the entire follow up period, as patients are strongly advised against pregnancy at that time.

If a reliable contraception method is not used during the follow-up, it could be initially unclear to clinicians as to whether a rising hCG level is caused by the patient becoming pregnant again, or by the continued presence of GTD.

[citation needed] In women who have a malignant form of GTD, hCG concentrations stay the same (plateau) or they rise.

Hysterectomy (surgical removal of the uterus) can also be offered[35] to patients > 40 years of age or those for whom sterilisation is not an obstacle.

More than 98% of women who become pregnant following a molar pregnancy will not have a further hydatidiform mole or be at increased risk of complications.

New medical data suggest that a significantly shorter waiting period after the hCG levels become normal is reasonable for approximately 97% of the patients with hydatidiform mole.

Especially women whose hCG levels remain significantly elevated are at risk of developing a repeat GTD.

Because successful term delivery might be possible, the pregnancy should be allowed to proceed if the mother wishes, following appropriate counselling.

The probability of achieving a healthy baby is approximately 40%, but there is a risk of complications, e.g. pulmonary embolism and pre-eclampsia.