Pregnancy places extra demands on a woman's heart. As early as the first trimester of pregnancy the volume of blood being pumped through the body increases by up to 50 percent and the heart rate increases by 10 to 15 beats per minute. All this extra work is to make sure that your growing baby has the nutrients it needs to grow in the womb. Naturally this places stress on the body and in some instances it causes raised blood pressure (hypertension). High blood pressure can occur in different ways and at different times during pregnancy:
Before Week 20: If you receive a hypertension diagnosis before week 20 of pregnancy it is likely that you already had high blood pressure before becoming pregnant. While some women will be aware of their condition, for others it comes as a shock and is only revealed through routine prenatal tests. If your blood pressure readings on two or more occasions are 140/90 mm Hg or higher, you will be told you have chronic hypertension (ongoing persistent high blood pressure). As the symptoms of hypertension are usually silent, there no need to beat yourself up about not recognizing the signs earlier!
After Week 20: Some women develop high blood pressure (bp) from the middle of the second trimester of pregnancy onwards. This is known as gestational hypertension (it used to be called pregnancy induced hypertension (PIH)). It is diagnosed if two or more readings show your bp is 140/90 mm Hg or above. If bp levels return to normal within 12 weeks after childbirth the diagnosis is changed to transient hypertension. If it continues after 12 weeks, the diagnosis is changed to hypertension.
Sudden Severe Spike: A sudden severe spike in bp after week 20 (higher than 160/100 mm Hg), with proteinuria (a urine test shows excess levels of protein) is a sign of preeclampsia. This is a highly dangerous pregnancy complication which can develop within hours and places the life of both mother and baby at risk. In the United States between 2 and 6 percent of all healthy pregnancies will develop preeclampsia. Furthermore the danger does not pass after childbirth, women should be careful to monitor their bp for 6 weeks postpartum.
What Are The Dangers Of High Blood Pressure In Pregnancy?
Before Week 20: The sooner you develop hypertension in pregnancy, the more likely you are to develop preeclampsia. For this reason, women with a preexisting diagnosis of hypertension are at highest risk and will need to be closely monitored. Additionally chronic hypertension can cause growth problems with your baby known as intrauterine growth restriction (IUGR).
After Week 20: Most cases of gestational hypertension are mild and do not cause any problems for mom or baby.
Preeclampsia: Visible signs of this condition include sudden weight gain (at least 2.2 pounds a week), swelling of the face and hands, sudden reappearance of morning sickness in late pregnancy, headaches and a pain in the belly (due to liver problems). If you experience these signs, immediately seek emergency care. It could save your life or that of your baby. Also, read about HELLP syndrome which is connected.
How Is It Treated?
Before Week 20: If you know you have high bp before becoming pregnant, work with your doctor to bring your condition under control before falling pregnant. Many women with chronic hypertension go on to experience problem-free pregnancies and give birth to healthy babies - but good prenatal care is particularly important. If you are already taking blood pressure drugs, your doctor may switch your medications because some (such as ACE inhibitor drugs) should not be taken by pregnant women. You may need to have extra ultrasound scans to monitor the growth of your baby, and your bp will be checked more regularly for signs of preeclampsia. Your doctor should recommend a home blood pressure monitor so you can keep an eye on your levels more frequently.
After Week 20: If you develop gestational hypertension you will not receive drugs (although the jury is still out on whether or not it's a good idea to give pregnant women medications if their readings only indicate mild raised bp). However you will be monitored closely in case it develops into preeclampsia. Again, home blood pressure monitoring should be considered, and ask your doctor for advice on hypertension prevention. You may also be told to lie on your left side to shift the weight of your baby off your major blood vessels.
Preeclampsia: The treatment depends on how far your pregnancy has progressed. The longer the fetus can develop in the womb the better. Initially the mother may be ordered complete bed rest and a protein rich diet. If this doesn't work, sedation and anticonvulsants may be prescribed. Ultimately, in many cases the only 'successful' treatment is delivery. Symptoms usually clear up within 48 hours of childbirth.
Who Is Most At Risk?
Your risk of developing hypertension in pregnancy are increased if you:
• Have a family history of preeclampsia.
• Have diabetes.
• Have a preexisting heart condition, see heart disease in pregnancy.
• Are obese.
• Are expecting twins or triplets (multiple births).
• Experiencing a pregnancy after 35 or in your teens.
• Have kidney disease, lupus or rheumatoid arthritis.
See our question: Will pregnancy raise my blood pressure?
Will My Blood Pressure Return To Normal After Childbirth?
Chronic Hypertension: If you had high bp before becoming pregnant, it is likely to remain high after delivery. You will need to continue your treatment for high blood pressure (if you were taking medications you will need to continue doing so) and eat a healthy diet and get some regular exercise.
Gestational Hypertension: Your bp will return to normal within 12 weeks of childbirth. However your risk factors for hypertension in later life will be higher.
Preeclampsia: Your bp should lower within 48 hours of childbirth and return to normal within 6 to 12 weeks.
How Can I Reduce My Risk Of Developing Hypertension?
As the causes of high blood pressure are still unknown, there is no sure way to prevent it. However, you can do something about controlling your risk factors during pregnancy by:
1. Eating a healthy diet, low in salt.
2. Exercise regularly.
3. Avoid drinking alcohol and smoking.
4. Drink at least 8 glasses of water a day.
5. Raise your feet as much as possible during the day.
6. Avoiding drinking coffee or other drinks with caffeine.
7. Get plenty of sleep.
8. Ensure you establish a good relationship with your pregnancy healthcare team and start your prenatal care immediately.
9. Read our list of pregnancy tips for other advice.