What is high blood pressure?
High blood pressure (or hypertension) in pregnancy is one of the leading causes of death and serious illness in pregnant women and babies worldwide. Therefore, knowing if you have high blood pressure and following all suggestions to treat it and monitor the pregnancy are extremely important.
Whenever blood pressure (BP) is checked, there are two numbers that are measured. The top number is the systolic number, which measures when the heart beats. The second number is the diastolic number, which measures when the heart rests. High blood pressure in pregnancy is diagnosed when a woman has either a systolic BP of 140 mmHg or higher, a diastolic BP of 90 mmHg or higher, or when both values are high on two separate blood pressure checks at least 4 hours apart.
Any patient who is known to have high blood pressure prior to pregnancy or who is diagnosed with high blood pressure before 20 weeks gestation is considered to have chronic hypertension. High blood pressure that is diagnosed after the 20th week of pregnancy is labeled as one of the following:
- Gestational hypertension – high blood pressure without any signs that it is affecting the kidneys.
- Preeclampsia – high blood pressure with signs of kidney damage or other organ damage, like the liver, lung, or central nervous system. Symptoms may include headache that doesnt improve with treatment, nausea/vomiting that suddenly starts late in pregnancy, blurry vision or seeing spots, difficulty breathing, pain in the upper abdomen, and swelling in the hands or face.
- Eclampsia – this is the same as preeclampsia but women also have seizures that are related to the high blood pressure.
Women who are diagnosed with chronic hypertension can also develop preeclampsia later in the pregnancy. The difference is generally determined when there is a sudden increase in blood pressure that had previously been well controlled, with or without medication, and when there is new kidney damage or signs/symptoms of preeclampsia.
There is also a rare, severe type of preeclampsia called “HELLP syndrome“. HELLP stands for Hemolysis, Elevated Liver enzymes, and Low Platelets. This is a severe type of preeclampsia that affects the liver and different types of blood cells that can cause a woman to have internal bleeding. HELLP is considered a medical emergency because both a woman and her baby can die from this disorder.
How common is high blood pressure during pregnancy?
In the US, 5% of pregnant women will have chronic high blood pressure during pregnancy. As many as 40% of these women will also develop preeclampsia during pregnancy.
Gestational high blood pressure is the most common type of high blood pressure seen in pregnancy. Six to 17 percent of women will develop gestational high blood pressure during their first pregnancy but fewer women will get it who have been pregnant before, only 2-4%. Obese women, women who had preeclampsia in a previous pregnancy, and women who are pregnant with more than one baby (twins, triplets, etc.) have a higher chance of getting gestational high blood pressure.
Approximately 3% of pregnancies in the US are affected by preeclampsia. It occurs more often in women who are pregnant with their first baby or who had preeclampsia in a previous pregnancy. Other risk factors for developing preeclampsia occur in women with any of the following:
- Chronic hypertension
- Family history of preeclampsia
- Are over the age of 40
- Used in vitro fertilization to get pregnant
- Are pregnant with more than one baby- twins, triplets, etc.
- Have lupus
How is high blood pressure during pregnancy diagnosed?
At each prenatal visit, both blood pressure and a urine sample are checked. If the blood pressure is high or there is protein found in the urine, then blood tests are taken to test how well the kidneys and liver are working and to measure the hemoglobin and platelets, two different blood cell types. These tests, along with how far along a woman is in her pregnancy (gestational weeks), can be used to determine which type of high blood pressure a woman has (i.e. chronic hypertension, gestational hypertension, preeclampsia).
Women who have gestational high blood pressure or are being evaluated for preeclampsia may be asked to collect their urine for 24 hours to get a better idea about how the kidneys are working. This can be done at home but is sometimes done with the woman in the hospital.
Other tests that may be done are an ultrasound to measure how well the baby is growing and a non-stress test, which looks at how well the baby is doing by listening to the babys heart for at least 20 minutes. If there is any concern that the baby is not doing well, then additional tests may need to be performed.
Does high blood pressure cause problems during pregnancy?
Women who have high blood pressure prior to getting pregnant and those that develop it during pregnancy have a higher chance of complications during pregnancy. Some of these complications include:
- Higher risk of developing gestational diabetes
- Placental abruption: An abruption is the separation of the placenta from the uterus before the baby is delivered. It is a medical emergency because it can cause life-threatening bleeding for the mother and deprives the baby of oxygen that can lead to death of the baby.
- Preterm delivery: Any baby born before 37 weeks gestation. Babies who are born preterm are usually delivered early to prevent life-threatening complications to both the mother and baby that are the result of the high blood pressure.
- Postpartum hemorrhage: Higher than average bleeding after delivery that usually requires treatment to decrease the bleeding.
- Cesarean section delivery
Other risks to the pregnant womans health are the development of heart failure, stroke, or kidney disease. Because of the seriousness of many of these complications, women who have high blood pressure in pregnancy usually have more visits with their doctor and closer monitoring of the baby. This is done to help diagnose any problems early and limit the potential harm to both the mother and her baby.
Does high blood pressure during pregnancy cause problems for the baby?
There is some evidence that women who have high blood pressure before they get pregnant or who develop it early in the pregnancy have a higher chance of having a baby with a birth defect, especially a heart defect. Other defects that have been seen are in the gastrointestinal tract, sexual organs, urinary system, and muscle/bones. This risk does not appear to be related to the medications used to treat high blood pressure because it has been seen in women not taking any medications.
Other problems t
hat can occur are poor growth of the baby, the need to deliver the baby early because of severe blood pressure problems, and stillbirth. Because of these problems, most women who have high blood pressure in pregnancy will have fetal testing to check for the well-being of the baby and detailed ultrasounds looking for birth defects and appropriate growth of the baby.
What to consider about taking medications when you are pregnant or breastfeeding:
- The risks to yourself and your baby if you do not treat the high blood pressure
- The risk of uncontrolled high blood pressure if you stop taking your medication or if you switch to a different medication.
- The risks and benefits of each medication you use when you are pregnant
- The risks and benefits of each medication you use when you are breastfeeding
What should I know about using medication to treat high blood pressure during pregnancy?
Women who have high blood pressure before pregnancy will generally need to continue taking medication during the pregnancy. This is to help decrease the chances that either the woman or her baby will develop complications during the pregnancy. However, early in pregnancy, many women will be able to decrease their medication doses because of a natural drop in blood pressure during the first half of pregnancy. Blood pressure tends to naturally increase after 20 weeks, so medications may need to be increased during the second half of pregnancy.
Not all women who develop high blood pressure during pregnancy will need to take medication. There is evidence that women who take medication for mild high blood pressure still have the same risk of getting severe preeclampsia, delivering the baby preterm, having a poorly developed baby, and death for the baby. Since these risks do not decrease, many expert physicians dont feel that the risks of exposing the mom and baby to high blood pressure medications are warranted. These women are usually monitored closely for any signs of worsening blood pressure or newly developing pregnancy problems.
However, women who have severe high blood pressure are at risk of serious complications like stroke, heart failure, pulmonary edema (water in the lungs making it difficult to breathe) and even death, so it is necessary to treat their blood pressures.
Who should NOT stop taking medication for high blood pressure during pregnancy?
A woman taking a medication to treat high blood pressure before pregnancy should not stop taking the medication until she speaks with her doctor. However, it is important to seek medical care as soon as you know you are pregnant. Certain medications used to treat high blood pressure carry birth defect risks, so these are generally switched to a medication with lower risks to the developing baby.
If you have chronic high blood pressure and are wanting to get pregnant, it is best to discuss this with your doctor early on. Many medications that pose a risk to the pregnancy can be switched to safer medications even before you get pregnant.
What should I know about choosing a medication for my high blood pressure during pregnancy?
Many medications used to treat high blood pressure are thought to pose little risk to the mother or baby. The most commonly used medications are labetalol, nifedipine, and methyldopa, but a number of medicines from the following drug classes can be used: beta-blockers, calcium channel blockers, or clonidine.
There are certain types of medications that should be avoided during pregnancy. Most diuretics, like furosemide or hydrochlorothiazide, must be avoided because they can decrease a womans blood volume too much, which can then decrease the amount of nutrients the baby receives. Spironolactone is avoided during pregnancy as well because it can limit the amount of male-type hormones made and prevent a male baby from developing normal sex organs.
ACE inhibitors such as benazepril, lisinopril, and enalapril, should be avoided during pregnancy because they may cause birth defects. Side effects of these medications when used in pregnancy include low amniotic fluid, poorly developed lungs, poor growth of the baby, abnormal development of the arms and legs, facial deformities, and abnormally grown skull bones.
No matter which medicine you are taking for your high blood pressure, it is important to understand what effects it may have on your pregnancy. The best way to learn about your medications is to speak with your doctor during your prenatal visits.
You may find Pregistrys expert reports about the individual medications to treat hypertension here. Additional information can also be found in the sources listed at the end of the report.
What should I know about taking a medication for my high blood pressure when I am breastfeeding?
The majority of women who develop high blood pressure in pregnancy will not need to be treated after the baby is delivered. A small number of women will require blood pressure treatment for a few weeks after birth but they can stop the medication once their blood pressure returns to normal. Women who had high blood pressure before pregnancy and those who developed it early in pregnancy will generally require long-term treatment.
Women who need to continue treatment after the baby is delivered and desire to breastfeed have many safe medication choices that can be used to treat their blood pressure while nursing. Most medications used to treat high blood pressure are considered safe to use while nursing. The amount of medication that passes into the breastmilk can vary, even within the same drug class. It is recommended to use a medication with the lowest transfer into breastmilk.
The following medication types are generally considered safe for use during breastfeeding:
- Calcium channel blockers like nifedipine, verapamil, and diltiazem are found in low levels in breastmilk.
- ACE inhibitors like lisinopril, captopril, and enalapril are found in low levels in breastmilk, however, there isnt a lot of information available about these medications during breastfeeding.
- Diuretics like spironolactone, hydrochlorothiazide, and furosemide are considered safe for breastfeeding but they can reduce a womans milk supply so they are not used very often.
Medications in the beta-blocker or alpha/beta-blocker classes have varied safety for use during breastfeeding. Propranolol, metoprolol, and labetalol have the lowest transfer into breastmilk and are generally the preferred medications to use.
Atenolol and acebutolol are secreted into breastmilk at high levels and can have unwanted effects on the nursing baby. Therefore, the American Academy of Pediatrics recommends avoiding these medications in nursing mothers. Carvedilol and bisoprolol are also generally avoided because there isnt any information about their use in nursing mothers.
What alternative therapies besides medications can I use to treat my high blood pressure during pregnancy?
There are no alternative treatments that are effective for lowering blood pressure. Studies have evaluated low salt diets, limiting activity, or bed rest on blood pressure but have found these dont help lower blood pressure.
everal supplements have been studied to see if they can be used to decrease the chances of developing preeclampsia. Vitamin E, vitamin C, and calcium have not been found to decrease a pregnant womans chances of developing preeclampsia.
Low-dose aspirin (60-80mg per day) has been shown to slightly decrease a womans risk of developing preeclampsia. This may be considered for women who developed preeclampsia before 34 weeks gestation in a previous pregnancy or those with certain types of high blood pressure that developed prior to pregnancy. There are risks associated with taking aspirin in pregnancy, so this must be discussed with your doctor before it should be used.
What can I do for myself and my baby when I have high blood pressure during pregnancy?
The best thing you can do for yourself and your baby during your pregnancy is to get regular prenatal care. Pregnancies complicated by any type of high blood pressure will require more frequent visits to your doctor and regular testing of the baby to make sure they are doing well. These can often be time-consuming and require a great deal of effort on your part but they are an important part of keeping both you and your baby safe and healthy.
It is important to tell your doctor about any new problems that you may have as soon as possible. Symptoms that may be a sign that your blood pressure is worsening include headache that doesnt improve with treatment, nausea/vomiting, blurry vision or seeing spots, difficulty breathing, pain in the upper abdomen, and swelling in the hands or face. You should call your doctor right away if you experience any of these symptoms.
Resources for high blood pressure during pregnancy:
For more information about high blood pressure during and after pregnancy, call womenshealth.gov at 800-994-9662 (TDD: 888-220-5446) or contact the following organizations:
- American College of Obstetricians and Gynecologists
- American College of Cardiology
- Society for Maternal-Fetal Medicine
- Mayo Clinic