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In my work, as an Obstetrician I see Pregnancy induced hypertension, also known as preeclampsia almost daily. It is a condition characterized by elevated blood pressure during pregnancy, in a person who does not have high blood pressure before pregnancy. In addition, there is an elevated hematocrit (percentage of red blood cells in the blood over plasma) loss of albumin (a plasma protein) in the urine and edema (swelling).

The cause of Pregnancy induced Hypertension (PIH) has been a medical mystery for years. No other mammal has a condition like this, thus; animal models have been very difficult to create. All kinds of theories have been postulated. From excessive weight gain in pregnancy, which is really an effect and not a cause, to excessive intake of salt, to poor nutrition.

Today, the belief is that the condition is of immune origin. The fetal cells in the placenta fail to penetrate into the walls of the branches of the uterine artery (spiral arterioles) that nourish the placenta; as a result, the placenta does not get enough oxygen and nutrients and, to compensate, it secretes a peptide (small protein) that increases maternal blood pressure, to increase the blood flow over the placenta and thus supply the growing fetus with its needs of oxygen and nutrients.

As a result of the action of this peptide, the lining of the capillaries (endothelium) is damaged, and fluid and protein seeps out. This leads to swelling and loss of protein (albumin) in the urine. The loss of albumin worsens the process by making the blood unable to "suck up" the fluid that leaks from the capillaries, increasing the swelling some more. This concentrates the blood (Increases the hematocrit) and increases the blood viscosity, the more viscous (thicker) blood flows more slowly through the arterioles and leads to further releases of the peptide with further increases in blood pressure.

The condition progressively worsens as the pregnancy moves along. Delivery is the only treatment and solution of the condition. All other interventions are just meant to "buy time" until the baby is ready for birth. Eventually, either the pregnancy reaches term (in milder cases) labor ensues and the mother delivers, or in more severe cases, delivery needs to be induced, when the baby's lungs are more or less mature.

Untreated severe PIH or preeclampsia can lead to seizures (eclampsia) and even maternal and/or fetal death.

Medical intervention is generally threefold: Magnesium sulfate to prevent seizures, blood pressure medications to lower the blood pressure and steroids to mature the baby's lungs more rapidly.

There are two non-medical interventions that help; Bed rest in the left (preferred) or right lateral position, because it increases blood flow to the uterus and drink lots of water, because dehydration thickens the blood even more.

Salt restriction is not helpful and can make things worse. Water pills also worsen the condition and are contraindicated.

All of the above does not apply to chronic hypertension in pregnancy (High blood pressure diagnosed before pregnancy) That is a totally different disease.

Learn more about this author, Pedro Miranda.
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