Terminology
Until recently, toxemiawas the term being used to describe hypertension (high blood pressure) that began in pregnancy. This condition was believed to be caused by toxins derived from the products of conception circulating in the blood. More recently the terms pre-eclampsia and eclampsiaare being used to describe the syndrome of hypertension, edema (fluid retention), and proteinuia (protein in the urine).
Preeclampsia and eclampsia are two categories of Gestational Hypertension, one just a further progression of the process than the other.

How common is it?
Gestational Hypertension (GH) is a common complication; it is seen in 5-7% of all pregnant women. It may be more common in certain groups, including young women pregnant for the first time, women with chronic hypertension, and women from low socioeconomic backgrounds. GH also tends ot recur in up to one third of the women, and some women continue to have hypertension indefinitely after the pregnancy.

How do I know if I have this?
Preeclampsia (the earlier stage of GH) is characterized by an elevation in blood pressure, protein in the urine, and/or edema after the 20th week of pregnancy. Blood pressure is checked regularly in the doctor's office from the first visit on to evaluate whether there have been any changes. Weight is also checked at every visit. Of course, you are expected to gain weight while pregnant but sudden, excessive weight gain that appears to be largely due to excess fluid in the tissues can be a sign of preeclampsia. Your urine will also be checked every visit for protein.
Other symptoms that may occur with preeclampsia include: severe, continuous headache; swelling of the face or fingers; dimness or blurring of vision; persistent vomiting; decreased urine output; epigastric pain (pain between the breasts just over the stomach).

What can be done about GH?
Mild preeclampsia can be treated by rest, most likely bedrest. The mom should also focus on staying relaxed, eating a healthy diet and drinking lots of fluids. If this restricted activity doesn't keep mom's blood pressure from rising she may have to come into the hospital for treatment with medications that will protect the mom from the effects of eclampsia like seizures. Magnesium Sulfate is the most common medication used for this purpose and must be given intravenously. If GH cannot be controlled by other means then the only way to control the progression of this syndrome is for the baby to be born. Both mother and baby could die if birth does not occur once symptoms become serious.

What is HELLP syndrome?
Preeclampsia can rapidly progress to a syndrome called HELLP. HELLP stands for hemolysis, elevated liver enzymes, low platelet count). This is an emergency situation that requires immediate delivery of the fetus whether or not it is viable. For more on HELLP syndrome go here.