Updated: Aug 22, 2021
Hypertension and pregnancy are terrible together. We think of hypertension as a disease that has to be lived with, but it actually takes lives in pregnancy. It's a leading cause of death of pregnant women all over the world.
About a tenth of pregnant women in the USA suffer from hypertension. According to a study involving over 7 million births hypertension is the most common cause of death among pregnant women and recent mothers, after hemorrhage.
It's disturbing that the number of women dying during pregnancy and in the six weeks following (called the maternal mortality rate) has doubled in the USA after 2000. While causes like sepsis and venous thromboembolism have reduced in frequency, hypertension is regrettably frequent.
So it is somewhat surprising that we don't talk much about it. We know that increased blood pressure is hypertension, but how much is too much? What are the dangers for pregnant women?
What is Considered Hypertension During Pregnancy?
Increased blood pressure is hypertension, of course, but the values are different during pregnancy.
The American College of Obstetricians and Gynecologists (ACOG) defines gestational hypertension as "a systolic blood pressure of 140 mm Hg or higher and/or a diastolic blood pressure of 90 mm Hg or higher" after week 20 of pregnancy.
The American College of Cardiology and American Heart Association (ACC/AHA) criteria diagnose hypertension as systolic blood pressure of 130 mm Hg or higher, a diastolic blood pressure of 80 mm Hg or higher, or both. These are the cutoffs used for the general population.
The difference is significant Dr. Natalie Bello and colleagues found that using the ACC/AHA criteria classified 28% of pregnant women as having hypertension, compared to 10% when using the ACOG criteria.
Should All Hypertension in Pregnancy be Treated?
According to a review by Dr. Lawrence Leeman , treating mild, pre-existing hypertension during pregnancy carries no benefits for the mother or fetus and is not recommended. In fact, lowering the blood pressure may reduce the blood supply through the placenta, harming the fetus.
The body controls the blood pressure within narrow limits. If it falls too low, blood won't reach the organs and tissues. Reducing blood pressure during pregnancy may sometimes reduce blood flow to the placenta, compromising the fetus's oxygen supply and nutrition.
Why is Pregnancy Hypertension so Alarming?
High blood pressure has several dangers, some specific to pregnancy:
Preterm labor and birth
Abruptio placentae (separation of the placenta; very dangerous for the baby)
Increased chances of a cesarean birth
Poor blood flow through the placenta, reducing nutrition to the fetus
Poor growth of the baby
Preeclampsia and eclampsia
Types of Hypertension in Pregnancy
If you already had high blood pressure before getting pregnant, or it is detected before completing 20 weeks of pregnancy, it is considered chronic hypertension.
Gestational hypertension, or hypertension of pregnancy, is high blood pressure appearing after 20 weeks of pregnancy. The distinction is important because about half the women with gestational hypertension go on to develop preeclampsia.
Preeclampsia is high blood pressure together with proteins in the urine or other signs of organ involvement. The incidence of preeclampsia is rising. Women opting for pregnancy at later ages and a higher incidence of obesity are the likely causes.
One of the most dangerous complications during pregnancy, it occurs in 2-8% of pregnancies. It is diagnosed when there is high blood pressure associated with some signs of organ dysfunction:
Low platelet count (less than 100,000 x10(9)/L)
New-onset headache with no other cause and not responding to medicine
We don't fully understand the cause, but some proteins produced by the placenta are likely causative. What we do know is that preeclampsia is dangerous.
The Dangers of Preeclampsia
As the name suggests, preeclampsia is a precursor of eclampsia.
Eclampsia manifests as seizures and is life-threatening for mother and baby.
Good antenatal care, improved monitoring and treatment, and planned early delivery are now standard care for severe hypertension in pregnancy. Treatment to prevent seizures may be required.
Without anti-seizure treatment, eclampsia occurs in 2-3% women with preeclampsia. Eclampsia can be deadly; the mortality is 14%.
Eclampsia can start after delivery. This a dangerous situation, because it is generally believed that the hypertension of pregnancy is cured by delivery.
Other dangerous complications are pulmonary edema (fluid in the lungs), liver disorder including rupture and potentially fatal abdominal bleeding, and bleeding disorders.
The kidneys are often affected. Reduced urine production and kidney failure can occur.
The HELLP Syndrome
It is a severe form of preeclampsia and consists of:
Hemolysis (destruction of blood cells)
Elevated Liver enzymes (signifying liver injury)
Low Platelet count.
The HELPP syndrome carries a high mortality. The aim of antenatal care should be to prevent it.
What Should You Do?
If you have high blood pressure before pregnancy, let your obstetrician know. Also, let her know what drugs you are taking. Some of them may not be safe in pregnancy.
Meet your doctor twice a week for blood pressure measurement and other monitoring. Instruments to measure your blood pressure at home are also available.
Your doctor will order ultrasound, amniotic fluid indices, and other tests for fetal well-being from time to time.
Be regular in taking your medication.
If your blood pressure is not under control, or there are any danger signs, your doctor may want to hospitalize you for better monitoring and treatment.
Delivery at 37 weeks reduces the risk to both you and your baby. Delivery is considered a cure for the hypertension of pregnancy and the associated dangers.
How Can You Avoid Hypertension?
Lifestyle measures go a long way.
Be more physically active
Eat healthy food.
Avoid excessive weight gain during pregnancy.
Avoid alcohol and smoking.
Can You Birth Normally?
Yes, you can, usually. Hypertension does not preclude labor and normal delivery.
When is a cesarean delivery required?
Serious problems for the baby or mother, and delivery is not close
Seizures that are not controlled by medication
Dangerously high blood pressure uncontrollable by medication.
Are Drugs for Hypertension Safe in Pregnancy?
Your doctor will consider drug therapy carefully. The drugs you take in pregnancy have to be effective, not harm the baby, and not affect pregnancy.
Some drugs that are considered safe: hydralazine, alphamethyldopa, diuretics, calcium channel blockers, and labetalol.
Your doctor won't prescribe teratogenic drugs (those that cause birth defects in the baby) during pregnancy. Medicines that you are used to (for example, ACE inhibitors) may be changed.
If you are pregnant, and your blood pressure is high, watch for these signs.
Visual: seeing dark spots or bright lights; temporary blindness, complete or partial; blurring of vision; and inability to tolerate light.
Brain related: severe, persistent headache; drowsiness.
Lung related: difficulty in breathing.
Kidney related: infrequent urine passage; swelling of feet.
Liver related: pain upper part of the abdomen on the right.
If you have any of these, you must talk to your doctor quickly. It is important to remember that eclampsia and the HELLP syndrome can appear in the days after birth.
Pregnancy-induced hypertension is a danger to life, especially in regions where healthcare services are inadequate. Being vigilant about your own health will keep you safe from the dangers of this frequent complication of pregnancy.