The true cause of hyperemesis gravidarum is unknown. Case-control studies have found that the incidence of hyperemesis gravidarum is related to nutritional status, socioeconomics, and age. Age is a significant correlate in etiology, with the incidence of hyperemesis gravidarum being 10 times higher in women older than 40 years than in younger women, and age younger than plus years being a high-risk factor for the development of complete hyperemesis gravidarum, which predisposes women to fertilization defects at both ages. Partial gravidity is not associated with maternal age.

The two types of hyperemesis gravidarum have been shown to have their own genetic characteristics through cytogenetic and pathological studies

The so-called hyperemesis gravidarum is a condition in which the chorionic villi that make up the placenta become edematous and degenerate, forming many blisters of varying sizes that resemble bunches of grapes.

The incidence of hyperemesis gravidarum is about 1 in 1,000 pregnancies, and it occurs most often in women who become pregnant after the age of 40, especially in menopausal women. Because these women's ovaries are prone to produce unsound eggs and secrete abnormal hormones, and because the body lacks certain nutrients necessary for reproduction, it is difficult for a fertilized egg to develop normally, resulting in the formation of a gravidarium.

According to statistics, women over 40 years of age have a four to seven times higher incidence of hyperemesis gravidarum than young women, and are prone to malignant changes, hyperemesis gravidarum can become chorionic epithelial cancer. Once "choriocarcinoma" occurs, if the treatment is not timely and thorough, the prognosis is poor.

After two years of observation, if everything is back to normal after a thorough examination by a doctor, contraception can be stopped.