Do you know what your blood pressure is? If you are thinking about becoming pregnant or you already are, you should have your blood pressure checked to see if you have high blood pressure, also called hypertension. Hypertension is one of the most common complications of pregnancy that can affect you and your baby.
You have probably heard that normal blood pressure is “120 over 80” or less, where 120 is systolic (the top number) and 80 is diastolic (the bottom number). Hypertension is defined as either a systolic blood pressure (BP) of 140 or greater, or a diastolic BP of 90 or greater, or both.
Chronic (preexisting) hypertension
A blood pressure consistently over 140/90 prior to pregnancy is called chronic hypertension and is present in up to 5 percent of pregnant women. This can occur more commonly in patients with diabetes, kidney disease, family history of hypertension and obesity. It is a good idea to have your blood pressure checked before or in the early part of your pregnancy to see if you require medication or special monitoring. Women with high blood pressure prior to pregnancy are at increased risk of complications in pregnancy.
Risks in pregnancy
Women with chronic hypertension have a greater chance of developing a condition called preeclampsia during pregnancy. Preeclampsia is present when you spill too much protein in your urine and your blood pressure increases. It develops in 13 to 40 percent of patients with chronic hypertension and can lead to a seizure (eclampsia), slow growth of the baby, kidney and liver failure, bleeding of the placenta, and even loss of the baby. Careful monitoring of your blood pressure is important during the pregnancy to watch for signs and symptoms of this condition. There is also an increased risk of C-section, preterm delivery, low birth weight, admission to neonatal intensive care, placental bleeding, and fetal or neonatal loss.
Treatment with medication
In adults who are not pregnant, blood pressure medication is recommended. But for those who are pregnant, treatment is less clear. Few studies have been performed that address the precise blood pressure level at which medication is indicated during pregnancy for patients with chronic hypertension, and there is also concern for the possible harmful effects of medications on the developing fetus that need to be considered.
Not all patients with hypertension require medication. If your blood pressure is only mildly elevated (140-150/90-100), it is not necessary to be on medication. Too much or unnecessary medication can cause the blood pressure to be too low, resulting in lightheadedness, dizziness, or a small baby from decreased blood flow. Some antihypertensive medications can also cause birth defects.
Types of medications
Commonly used oral medications that have been shown to be safe in pregnancy include labetalol, nifedipine, methyldopa, and thiazide diuretics. Medications that should not be taken during pregnancy because they can cause birth defects are called angiotensin-converting enzyme (ACE) inhibitors like captopril, enalopril, lisinopril, and moexipril. Because 50 percent of pregnancies are unplanned, these medications and medications like them, should be avoided in women of reproductive age.
Women with chronic hypertension should be evaluated either before pregnancy or in early pregnancy to determine the best treatment and monitoring plan. Recommended baseline testing includes kidney function, liver function, platelet count, electrolytes and a measure of protein in the urine. For women found to have kidney or heart disease, blood pressures are kept lower during pregnancy to avoid worsening of the disease. Diabetes testing is often performed early in women with chronic hypertension and some require an EKG or ultrasound of their heart if they have severe hypertension or a history of hypertension for more than four years. This is also the time that medications can be reviewed and changed if necessary.
Prevention of preeclampsia
Low-dose aspirin (60-80 mg) taken during pregnancy in patients with chronic hypertension is associated with a lower risk of preeclampsia, lower preterm birth and improved fetal survival. The benefits are greater when low-dose aspirin is started early in pregnancy. Taking extra calcium during pregnancy (1000 mgs or more) has also been shown to reduce hypertension and preeclampsia by 50 percent in high-risk patients.
Blood pressure should be checked at least monthly in all pregnant patients. This is usually done at the doctor’s office but patients with chronic hypertension or with risk factors for preeclampsia (diabetes, kidney disease, obesity) should obtain a blood pressure cuff and check blood pressures at home on a regular basis. You can then call your doctor if you notice a change in the blood pressure pattern or show your doctor a list of blood pressures at each prenatal visit. Weight loss and low-sodium diets are not recommended strategies for lowering blood pressure during pregnancy.
Monitoring the baby
Women with chronic hypertension are at increased risk of having smaller babies and complications after delivery. The risk is 8 to 15 percent with mild hypertension and up to 40 percent with severe hypertension. The methods used to screen for decreased fetal growth are fundal height measurement and ultrasound. The fundal height is usually measured at each prenatal visit after 16 weeks gestation and an ultrasound is done if the fundal height is low. Depending on the patient’s level of hypertension and risk factors, regular ultrasounds are also done to monitor the fetal growth. Fetal testing with non-stress tests (NSTs), biophysical profiles (BPPs), and Doppler ultrasound is used in women with chronic hypertension if growth restriction (IUGR) or preeclampsia are diagnosed.
In women with chronic hypertension who have no complications like preeclampsia or abnormal fetal growth during the pregnancy, delivery can be considered between 38 to 39 weeks gestation. Delivery during this time results in good fetal outcomes while avoiding the risks of prematurity. Women with chronic hypertension who develop complications will likely require earlier delivery depending on the severity of the condition and other risk factors.
Women with chronic hypertension usually require medication after delivery. Blood pressures are often higher immediately after delivery than during the pregnancy. Medications should be adjusted to keep blood pressure below 160/100. Non-steroidal anti-inflammatory agents like ibuprofen should be avoided in the postpartum period in women with chronic hypertension or preeclampsia. Other pain medications can also be used.
Breastfeeding does not increase blood pressure. It is safe and recommended in patients with chronic hypertension who are on antihypertensive medications. The medications listed above are safe for women who are breastfeeding. Only atenolol and metoprolol (beta-blockers) are concentrated in breast milk and should be avoided.