High Blood Pressure During Pregnancy

What is considered high blood pressure during pregnancy?

In a healthy individual, the systolic blood pressure should ideally range below 120 mmHg while the diastolic blood pressure should be lower than 80 mmHg ^[1]. Ideally, the BP range should remain within these limits throughout the pregnancy. Having a BP reading over 140/90 mmHg is considered high blood pressure in a pregnant woman ^[2] while a BP reading above 120/80 and below 140/90 calls for a visit to your doctor.

High blood pressure and pregnancy: Is it an early sign?

Although a little high BP is quite common while pregnant, it is not considered an early sign as it can occur anytime in pregnancy. Women with blood pressure too high are more at risk of various complications.

Your Normal Blood Pressure while Pregnant

Your body produces around 1 liter of extra blood by the 24th week (sixth month) of pregnancy to transport oxygen and nutrients to the developing fetus and to carry the fetal waste products away ^[3]. As a result, your blood pressure may rise a little with your heart working extra hard to pump the additional blood. Progesterone (pregnancy hormone) relaxes the blood vessel walls to allow the extra blood to pass, which may lower your BP around the mid weeks of pregnancy. However, there is nothing to worry about as your BP becomes normal again in later third trimester ^[4]. Your doctor may get concerned only if your BP reading remains higher than normal over several weeks.

High Blood Pressure during Pregnancy Stage Chart

Severity Level ^[5]	Systolic Pressure ^[6]	Diastolic Pressure ^[6]
Pre-hypertension	120 to 139 mmHg	80 to 89 mmHg
Stage 1 (Mild)	140 to 149 mmHg	90 to 99 mmHg
Stage 2 (Severe)	160 mmHg or higher	100 mmHg or higher

What are the different types of high blood pressure in pregnancy?

The following classification depends on the underlying causes, possible outcomes and the stage of onset of the condition:

Pre-existing or chronic high blood pressure ^[6]
Gestational hypertension
Preeclampsia (earlier referred to as toxemia of pregnancy)
Preeclampsia superimposed on chronic hypertension ^[7]

What causes high blood pressure in pregnancy

As the name suggests, the pre-existing form refers to high blood pressure that continues from before pregnancy. High BP diagnosed before the 20th week is considered to be pre-existing and not caused by pregnancy ^[8]. On the other hand, gestational high blood pressure develops during pregnancy after the 20th week, with the exact triggering factors still remaining unknown. The pregnancy induced form may later advance to complications like preeclampsia, HELLP syndrome and eclampsia.

Risk Factors for High Blood Pressure While Pregnant

Chronic high BP or kidney disease before conceiving
First pregnancy
A family history of pregnancy induced hypertension ^[9]
Being younger than 20 years or older than 40 years
Twin pregnancy (2-3 times more at risk) ^[39]
Too much smoking and/or alcohol consumption
Overweight or obesity ^[5]
Thyroid and adrenal disorders
Diabetes
African-American race ^[8]
Drinking lots of water to stay hydrated
Consuming salt only as necessary ^[9]
Following a diet containing fresh fruits and vegetables ^[12]
Avoiding gaining too much weight in pregnancy ^[13]
Following a regular exercise routine
Avoiding alcohol, caffeine and smoking
Getting plenty of rest
Keeping your feet elevated when resting
Doing pre-natal yoga ^[40] and practicing relaxation techniques to reduce stress ^[14]

How to prevent high blood pressure during pregnancy?

Women suffering from chronic hypertension should consult a health care practitioner to lower the BP before planning to have a baby ^[7]. The above healthy lifestyle changes are also recommended for ensuring a healthy pregnancy. Taking calcium supplements (FDA recommended RDA of 1200 mg) is also believed to help to avoid extremely high BP (preeclampsia) in high risk pregnancies ^[12]; although, no supplements should be used without consulting the doctor.

What are the signs and symptoms of high blood pressure during pregnancy?

In many cases, it does not lead to any signs and the high BP is only detected during a regular pre-natal check-up ^[7]. But, you should look out for symptoms like:

Severe persistent headache ^[6]
Changes in vision (sensitivity to light, flashing lights, blurred vision or vision loss)
Dizziness
Severe upper abdominal pain (especially on your right side) ^[15]
Severe nausea and vomiting in later pregnancy
Sudden swelling (edema) of the face, hands and feet
Sudden weight gain (over 5 pounds a week) ^[15]
Reduced urination ^[8]
Lower back pain ^[16]
Chest pain
Breathing difficulty
Nosebleeds ^[41]

Make sure to call your doctor immediately in case you have one or more of the above signs as they may indicate serious complications like preeclampsia.

How is high blood pressure diagnosed during pregnancy?

Your blood pressure is checked as a routine procedure during the pre-natal visits to your doctor. High BP is diagnosed if:

Two BP readings taken 4 hours apart are 140/90 or higher ^[3]
The BP shows a reading of only the diastolic pressure of 110 or higher (a higher than normal diastolic reading is enough to diagnose high BP) ^[4]

You may be asked to stay at the healthcare facility for several hours so the doctor can monitor your BP on an hourly basis. Other tests like ultrasound scans, blood tests ^[17], urine tests, non-stress tests ^[8] and biophysical profile may be necessary for assessing the maternal and fetal health as well as for checking the heart and kidney functioning.

Urine tests are vital for detecting protein in the urine, which (along with high BP) confirms the diagnosis for preeclampsia ^[18]. Women who have high BP with no protein in the urine are also at risk of developing the complication.

High Blood Pressure during Pregnancy Differential Diagnosis

Systemic lupus erythematosus	Autoimmune thyroid disease in pregnancy	Primary hyperaldosteronism
Aortic coarctation ^[19]	Cushing syndrome	Nephrotic syndrome
Scleroderma	Diabetes mellitus in pregnancy	Protein c or s deficiency
Diabetic glomerulosclerosis	Hypertensive encephalopathy	Thrombotic thrombocytopenic purpura
Antiphospholipid antibody syndrome in pregnancy	Disseminated intravascular coagulation ^[20]	Pulmonary disease in pregnancy
Interstitial nephritisAcute and chronic glomerulonephritis	Gastrointestinal disease in pregnancy	Hematologic disease in pregnancy
Antithrombin deficiency	Hemolytic-uremic syndrome	Hyperthyroidism
Peripartum cardiomyopathy	Hydatidiform mole	Hypothyroidism

What are the risks of high blood pressure during pregnancy?

Effects on the baby

Lower than normal birth weight due to decreased blood flow to placenta that lowers the oxygen and nutrient supply to the developing fetus ^[15]
Various birth defects (especially neural tube defects and heart malformations) ^[22]

Dangers to the Mother

Developing preeclampsia, a serious complication that may endanger the lives of both mother and child ^[21]
Placental abruption ^[23]
Premature labor and delivery (before the 37th week of pregnancy) ^[37]
Miscarriage, especially in later pregnancy ^[38]
Elevated risk of stroke as well as various heart diseases, kidney disorders and diabetes in the mother in future ^[24]

How to reduce high blood pressure during pregnancy?

Close monitoring with tests and medications is necessary depending on how high the BP is and when it is diagnosed ^[18]. Mild cases of high BP are often managed by bed rest and going for frequent prenatal check-ups. ^[25]. The treatment for severe chronic or gestational high blood pressure involves both prenatal and postnatal care with its main object being preventing the condition from getting any worse ^[26].

Medication for Lowering High Blood Pressure during Pregnancy

Women with chronic hypertension are often prescribed medicines to keep their BP below the 149/90 mark. Those already on BP medication before conceiving should consult a doctor to determine whether it is safe to take the same medicine in pregnancy. Regular BP medications like ACE inhibitors, angiotensin II receptor blockers ^[27] and renin inhibitors are not recommended to pregnant women as they can cause serious side effects both in the mother and the baby (especially in the second and third trimesters) ^[28]. Possible risks include kidney damage and potassium accumulation in the mother as well as fetal death ^[23].

Medications considered safe during pregnancy include:

Methyldopa (taken orally)
Nifedipine (taken orally)
Hydralazine (intravenous)
Labetalol (intravenous) ^[32]

Magnesium sulfate is often used to prevent seizures (eclampsia) associated with extremely high blood pressure ^[29].

Natural Remedies

Regular home remedies used for managing high BP are often not recommended during pregnancy. Those considered relatively safe include herbal teas like dandelion, nettle and lime flower as well as fresh beetroot juice ^[30]. But, never consider any of these remedies without consulting your doctor.

Treatment of Severe Cases

Hospitalization may be necessary to prevent the condition from advancing to serious complications in women with unusually high BP readings. Early delivery by a c-section (cesarean section) or induction of labor is an option in women past the 38th week of pregnancy with preeclampsia. Those between the 34th and 37th week are monitored closely at the hospital for development and functioning of the fetal organs. Steroid medicines (e.g. betamethasone, dexamethasone) can be used for accelerating the fetal lung maturation so that the baby can be delivered as soon as possible.

Diet for High Blood Pressure during Pregnancy

The National Heart, Lung and Blood Institute (NHLBI) recommend the DASH Diet (Dietary Approaches to Stop Hypertension) ^[31] for lowering the sodium intake and fight high BP. Additionally, it increases the intake of calcium, potassium and magnesium, the three minerals known to help control BP. The principal food items included in this diet plan are whole grains, fresh fruits and vegetables, low-fat dairy, poultry, fish and meat products nuts, beans as well as small helpings of sweets.

Foods to avoid: Mainly fatty and salty foods ^[10] as sodium causes more fluid to remain in your body, requiring the heart to work harder ^[11]

Treatment of High Blood Pressure after Pregnancy

Although the blood pressure gradually comes down to normal after delivery in most women with severe high blood pressure (or preeclampsia) late in pregnancy, some women may need medical treatment even after the baby is born. In some cases, a woman may develop extreme high blood pressure along with abnormally high amounts of protein in the urine following pregnancy (postpartum preeclampsia) ^[35]. Like during pregnancy, magnesium sulfate is used to manage seizures after childbirth. Other antihypertensive medicines may also be prescribed while the patient may even have to stay at the hospital for a few days longer so the doctors can monitor their BP. It is recommended to consult your doctor regarding whether it is safe to breastfeed your baby while taking the medications ^[36].

How common is high blood pressure in pregnancy?

It affects 1 out of every 10 pregnant women ^[18]. Around 1 in every 20 woman has pre-existing high BP while 1 in every 20 women develops high BP without preeclampsia while pregnant. The high BP advances to preeclampsia in 2-8 pregnant women out of 100 while eclampsia develops in about 1 in 200 women ^[6].

High Blood Pressure ICD-9 and ICD-10 Codes

The ICD-9 code used for identifying high BP is 401 ^[33] while its ICD-10 codes are I10, I11, I12, I13, I15 ^[34]

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