Chronic Hypertension & Pregnancy
Chronic hypertension complicates about 5% of pregnancies, and this rate is increasing due to delayed pregnancy.
Chronic High Blood Pressure Pregnancy
Chronic hypertension is high blood pressure before pregnancy or diagnosed within the first 20 weeks of pregnancy. Additionally, if the 12-week postpartum checkup does not resolve the blood pressure.
In the first trimester, if a patient have severe hypertension will have a greater than 50% risk of developing superimposed preeclampsia. Hypertensive patients should undergo increased frequency of laboratory tests, ultrasound scans (to assess growth), and antenatal testing.
What are the chronic high blood pressure risk factors? Specific traits, conditions, or habits might increase your chances to develop hypertension called hypertension risk factors.
What are the symptoms of high blood pressure? Studies show one in every three adults has high blood pressure, but one-third of them unknowingly having hypertension. Therefore, you should not disregard hypertension symptoms, when experiencing them.
How is high blood pressure diagnosed? Blood pressure is a vital indicator of the overall health. For proper diagnosis, you should know the correct procedure for a hypertension diagnosis.
How does high blood pressure affect pregnancy? Chronic hypertension during pregnancy puts extra strain on your heart and kidneys and increases your risk towards heart disease, kidney disease, and stroke. Other possible complications include preeclampsia, premature birth, low birth weight, placental abruption, and cesarean delivery.
What can I do to have a healthy pregnancy? Even though hypertension during pregnancy is serious problem, most women have successful pregnancies. More frequent prenatal care is important for you and your baby’s health.
What is the difference between chronic vs. gestational hypertension?
On many occasions, it is difficult to know whether you have chronic hypertension or gestational hypertension. If you diagnose hypertension before 20 weeks of gestation, then it indicates you have chronic hypertension that affects 5% of pregnant women.
Gestational or pregnancy-induced hypertension is high blood pressure develops at 20 weeks of gestation or later. Gestational hypertension is hypertension develops during pregnancy and mostly goes away after childbirth.
Pregnancy complications in women with chronic hypertension
Although many chronic hypertensive women had a healthy pregnancy, they are at increased risk for various pregnancy complications such as superimposed preeclampsia, fetal growth restriction, placental abruption, preterm birth, and cesarean section.
Preeclampsia - 17 to 25% of women with chronic hypertension develop superimposed preeclampsia.
Fetal Growth Restriction - 10 to 20% prevalence of fetal growth restriction; estimated weight is less than the 10th percentile for gestational age–based population norms in women with chronic hypertension.
Placental Abruption - Chronic hypertension had a frequency of placental abruption of 1.56% compared with 0.58% in non-hypertensive women.
Preterm Birth and Cesarean Delivery - 12 to 34% preterm delivery among women with chronic hypertension but as high as 62 to 70% among women with severe hypertension (≥170/110 mm Hg two times at least 24 hours apart).
Management of chronic hypertension in woman planning for pregnancy
Pre-pregnancy care - Prenatal care of women with chronic hypertension should start before pregnancy that is even when they are planning to become pregnant. You should update your knowledge about the pregnancy risks and need to optimize your antihypertensive treatment and lifestyle change before conception. However, the majority of women who enter pregnancy with chronic hypertension have it unknowingly.
Women on angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) and planning to become pregnant has to discuss with their doctor to prescribe an alternative. It is because ACE & ARBs has increased risk towards congenital abnormalities, if taken during pregnancy. Women on chlorothiazide have to discuss with their doctor to prescribe an alternative, because chlorothiazide may increase the risk of congenital abnormality and neonatal complications. Atenolol and other beta-blockers should be avoided, because of its association with babies born small.
Methyldopa is considered as the first choice in pregnancy because of its limited effect on uteroplacental blood flow. Sometimes an alternative must be found because of elevated liver enzymes or complaints of a headache. Labetalol, a combined alpha-blocker, and beta-blocker is an alternative to methyldopa. It tolerates well and easy twice-a-day dosing schedule than methyldopa. Calcium channel blockers (nifedipine) are frequently used because of its use to stop premature labor. Diuretics have been in use for pregnancy despite its theoretical risk of preventing normal blood volume expansion.
During pregnancy care - Pregnant women with uncomplicated chronic hypertension should aim for a blood pressure less than 150/100 mmHg, do not lower diastolic below 80 mmHg. Pregnant women with target-organ damage secondary to chronic hypertension should aim for a blood pressure lower than 140/90 mmHg. There is concern that overly aggressive antihypertensive treatment may decrease fetoplacental perfusion and increase the risk for fetal growth restriction.
Recommend more frequent prenatal visits for pregnant women with chronic hypertension compared with healthy women to evaluate blood pressures, urine protein, fundal height, ultrasound (to the evaluation of fetal growth & amniotic fluid volume), and maternal symptoms.
Studies show antihypertensive treatment has not reduced superimposed preeclampsia, placental abruption, or growth restriction or to improve neonatal outcome. Every 10 mmHg drop in blood pressure in women taking antihypertensives was associated with a 145 g decrease in birth weight. Such drugs are methyldopa, acebutolol, atenolol, labetalol, metoprolol, oxprenolol, pindolol, propranolol, bendrofluazide, chlorothiazide, hydrochlorothiazide, ketanserin, hydralazine, isradipine, nicardipine, nifedipine, verapamil, and clonidine.
- Centrally acting agents - also called central adrenergic inhibitors, Methyldopa may have mild hypotension in babies in first two days of life. It has no obvious association with congenital abnormalities.
- Beta-blockers - Labetalol (rare mild hypotension in first 24 hours of life and rare hypoglycemia), Atenolol (low birth weight/placental weight and decreased fetal heart rate), Metoprolol, Oxprenolol, and Pindolol. All beta-blockers has no obvious association with congenital abnormalities.
- Alpha-blockers - Prazosin has no obvious association with congenital abnormalities.
- Calcium-channel blockers - Nifedipine, Amlodipine, and Verapamil, has no obvious association with congenital abnormalities.
- Diuretics - Chlorothiazide (Possible association with congenital abnormalities, neonatal thrombocytopenia, neonatal hypoglycemia/hypovolemia, and maternal/fetal electrolyte imbalances), Bendroflumethiazide (Maternal hypovolemia), and Furosemide (No obvious effects).
- Vasodilators - Hydralazine (no congenital abnormalities association) and Diazoxide (may inhibit uterine contractions, maternal hypotension, and neonatal hyperglycemia).
Large, randomized, placebo-controlled studies have shown that the use of calcium, low-dose aspirin, or antioxidant (vitamin C and E) does not confirm decrease in the preeclampsia risk. Still, you can prefer to use cranberry juice, fish oil (omega-3 fatty acids), flaxseed oil, garlic, ginger, ginkgo Biloba, green tea, and natto to lower your risk towards preeclampsia.
For women with chronic hypertension managing their BP without medications, the timing of delivery is recommended at 38 to 39 weeks of gestation. For women with chronic hypertension on medications, the recommended delivery is at 37 to 39 weeks of gestation. For women with chronic hypertension on medications and difficult to control or diagnosed with superimposed preeclampsia, the recommended delivery is at 36 to 37 weeks of gestation. If markers of severe preeclampsia were present then recommended delivery is at 37 weeks of gestation or earlier.
Post-pregnancy care - Based on the benefits of breastfeeding, women with chronic hypertension even on antihypertensive medications should breastfeed. Although most antihypertensive medicines have measurable amounts in the breast milk, which is lower than in maternal plasma.
Suggested first line antihypertensive drugs that are safe in breastfeeding mothers include labetalol, nifedipine, and enalapril.
Higher breast milk levels of atenolol are reported and noted lethargy and bradycardia in newborns breastfed by mothers on atenolol. Thus, a breastfeeding mother should avoid atenolon and change to other options. The diuretics use during breastfeeding is not recommended because they may decrease breast milk production.