Pregnancy-related hypertension is dangerous to both the mother and the fetus. Luckily, many pregnant women with hypertension have had healthy babies without any serious problems.
Chronic hypertension complicates 3 to 5% of pregnancies. Gestational hypertension complicates 6 to 7% of pregnancies. Preeclampsia complicates 2 to 8% of pregnancies.
What is normal blood pressure during pregnancy? Normal blood pressure during pregnancy is usually somewhere close to 120/80 mm Hg.
What is high blood pressure during pregnancy? A blood pressure of over 140/90 mm Hg, or systolic (top number) 15 points more than before pregnancy is considered as high blood pressure during pregnancy.
Can I have a healthy pregnancy with hypertension? Even though hypertension and preeclampsia during pregnancy are serious, most women have successful pregnancies. More frequent prenatal care is important for you and your baby’s health.
What changes happen to your blood pressure during pregnancy?
During pregnancy, blood volume slowly rises by about 40 to 50% through increased aldosterone. The rise in blood volume, in turn, increases heart rate (by about 15 beats/min), stroke volume, and cardiac output (by about 50% during the first trimester).
The left ventricle (left side of the heart does a significant amount of pumping) becomes thicker and larger. This temporary change allows the heart to work harder to support the increased blood volume.
The kidneys release increased amounts of vasopressin, a hormone that leads to increased water retention. The renin-angiotensin system is up-regulated, causing increased aldosterone levels, which in turn increases blood pressure.
The systemic vascular resistance decreases slightly due to smooth muscle relaxation and vasodilation caused by elevated progesterone. Diastolic blood pressure drops between 12 to 26 weeks and increases again to pre-pregnancy levels at around 36 weeks.
During early pregnancy, from 5th-week pregnancy to the middle of the second trimester, the blood pressure decrease because pregnancy hormones dilate blood vessels.
Thus, the resistance to blood flow is lower, and there should be a drop in blood pressure. Blood pressure drops slightly early in pregnancy, then returns to pre-pregnancy levels in the third trimester.
4 types of pregnancy-related hypertension
- Chronic Hypertension– Women who have high blood pressure over 140/90 mmHg before pregnancy or before 20 weeks of pregnancy. And their hypertension persists even after delivery.
- Gestational Hypertension– High blood pressure develops after 20 weeks of pregnancy. And their hypertension mostly vanishes after delivery.
- Preeclampsia – Both chronic and gestational hypertension can lead to preeclampsia with the presence of protein in the urine after 20 weeks of pregnancy. If not treated immediately, this can lead to serious complications for both mom and baby.
- Chronic hypertension with superimposed preeclampsia - Superimposed preeclampsia is characterized by worsening of high blood pressure and protein in the urine in chronic hypertension patients with the vascular or renal disease.
What pregnancy complications high blood pressure can cause?
Pregnancy-related hypertension puts extra strain on your heart and kidneys and increases your risk towards heart disease, kidney disease, and stroke.
Other possible complications include the following:
- Preeclampsia – Hypertension developed before 30 weeks of gestation will have 50% chance for preeclampsia. It is a condition characterized by high blood pressure and protein in your urine. Without proper, timely treatment, preeclampsia can cause vision changes, kidney or liver problems, congestive heart failure, stroke, and seizures. In some rare instants, it can lead to life-threatening eclampsia and HELLP syndrome. Eclampsia can cause seizures and leads to coma. HELLP syndrome develops when you have serious blood and liver problems.
- Premature birth - If the placenta is not furnishing enough nutrients and oxygen to your baby. A pregnant woman with high blood pressure or preeclampsia requires ti give birth too early, even before 37 weeks of pregnancy. Studies show 62 to 70 % of women with severe hypertension deliver early. 28 % of women with hypertension have their baby before 37 weeks pregnant.
- Low birth weight – High blood pressure decrease the nutrient flow to the baby through the placenta, thus may cause growth problem to the baby. So baby may born with low weight, less than 5 pounds 8 ounces (2.5 kg).
- Placental abruption – It is premature separation of placenta from the uterus wall before birth. Your baby stops getting enough oxygen and nutrients in the womb. You may have bleeding from the vagina. It is a medical emergency require immediate treatment. For mild hypertension, the risk of placental abruption is about 1 in 100 women. For severe hypertension or preeclampsia, the risk is 5 to 10 percent.
- Cesarean delivery – High blood pressure during pregnancy may lead to cesarean birth (also called C-section). Surgery to take out a baby through a cut your doctor makes in your belly and uterus. A cesarean delivery has the risks of infection, internal organs injury, and bleeding. About 4 out of 10 women with high blood pressure give birth by C-section.
What happens to your hypertension after delivery?
- Chronic (preexisting) hypertension: Your blood pressure will stay high after delivery, and you will need to take medicine to control it. Undiagnosed hypertensive women may appear as normotensive in early pregnancy. Because blood pressure normally drops in the first trimester. When hypertension is noted later in the pregnancy, it may be considered as gestational.
- Gestational hypertension: Your blood pressure back to normal within a few weeks after delivery, but your chances to develop chronic hypertension later in life. In people with gestational hypertension, blood pressure usually normalizes in six weeks of postpartum.