The classic signs and symptoms of complete mole are:
Incomplete moles do not give rise to the above mentioned classical signs and symptoms. Vaginal bleeding and absence of fetal heart sounds mimic an incomplete or missed abortion.
The use of advanced imaging techniques such as high resolution ultrasonography routinely during the course of pregnancies has revolutionized the diagnosis of hydatidiform moles. As a result, molar pregnancies are now easily detected in the first trimester and the classical clinical presentation is rarely seen  .
Upon physical examination, a molar pregnancy classically appears too large for gestational age. Fetal heart sounds are also absent.
A number of laboratory investigations are also helpful in establishing a diagnosis of molar pregnancy.
In both complete and partial moles, ultrasonography is the criterion standard for establishing the diagnosis. The classical image of hydropic chorionic villi seen in these cases is referred to as snowstorm pattern.
If diagnosed and managed early, there is no risk of mortality in complete and partial moles.
Hydatidiform moles may give rise to malignancy (choriocarcinoma). Malignancy is more common in complete moles (15 to 20%) as compared to partial moles (2 to 3%). These malignancies however, are almost 100% curable.
Hydatidiform moles are a very frequent complication of pregnancy. In the United States, the incidence is approximately 1 in 1200 pregnancies . Molar pregnancies are more common at the extremes of reproductive age (i.e. in early teenage and close to menopause)  .
Complete and partial moles result from slightly different pathophysiological mechanisms.
Complete moles are named so because they do not contain any fetal tissue and consist only of hyperplastic trophoblastic tissues. There is marked swelling and edema in all the chorionic villi. The genotype of the mole is either 46,XX or 46,XY, the former accounting for almost 90% of the cases  .
In most of the cases, the genetic material in a complete mole is derived paternally. Such a mole is termed androgenic complete mole and is formed when an egg that has lost its chromosomes is fertilized by either one or two sperms. The former type is known as a homozygous androgenic complete mole. After a single sperm fertilizes the egg, the haploid genetic content of that sperm is duplicated. It is the more common of the two, accounting for 80% of the cases. This type of mole is always genotypically female (46,XX). On the other hand, complete moles may be formed when two sperms fertilize an egg that has lost its chromosomes. Such a mole is termed heterozygous complete mole. These moles may be 46,XX or 46,XY genotypically and account for only 20% of the cases.
Very rarely, complete moles may be even when both maternal and paternal genes are present in the fertilized egg. Failure of maternal imprinting however, suppresses the maternal genes and they fail to express themselves. Such moles are called biparental complete moles .
Partial moles are formed when an egg with normal chromosomal content is fertilized by two sperms to get a triploid genotype (69,XXX or 69,XXY) . Partial moles often contain fetal tissues; most commonly fetal erythrocytes and vessels. Unlike complete moles, villous edema is confined to patches of chorionic villi.
Apart from maintaining a healthy level of animal fat and carotenes in the diet, there is no documented preventive measure against the development of molar pregnancies.
Gestational trophoblastic disease is a spectrum of tumor and tumor-like conditions in which there is proliferation of trophoblastic tissue. This includes hydatidiform moles, invasive moles, choriocarcinomas and placental-site trophoblastic tumor.
Hydatidiform mole (or hydatid mole) can be defined as abnormal conception characterized by excessive proliferation of placental trophoblastic tissue. The chorionic villi become swollen and edematous and form grapelike masses. Hydatidiform mole may be designated complete or incomplete depending upon the karyotype of the abnormal tissues, the fraction of villi involved and the presence of fetal tissues.
Hydatidiform mole is an abnormal pregnancy in which instead of a fetus, there is excessive growth of placental tissue. The mole grows much more rapidly than a normal fetus and it becomes necessary to abort the pregnancy and clear the uterus. Molar pregnancies are now detected very early due to advanced ultrasound imaging techniques. There is no risk for mortality. In some molar pregnancies, there is risk for the development of cancer. Such cancers however, are readily treatable.