Hypertension and pregnancy: what our experts have to say!

High blood pressure (HTA) is still one of the main modifiable risk factors for cardiovascular disease (CVD). In women, pregnancy can be a specific risk factor for the development of hypertension, due to a disturbance in the production of the placenta. In women already being treated for hypertension, the desire to become pregnant means that certain antihypertensive treatments contraindicated in pregnancy must be modified, and their hypertension is an identified risk factor for placental disorders, justifying close monitoring of their pregnancy.
What do the authors of this publication tell us?
American epidemiology.
Among women of childbearing age in the United States, hypertension affects 13% of 20- to 34-year-olds and 30% of 35- to 44-year-olds. Outside pregnancy, blood pressure control is very poor, with only 16% of women having systolic BP (SBP) < 130 mm Hg and diastolic BP (DBP) < 80 mm Hg.
Over the last ten years, the frequency of hypertension during pregnancy has almost doubled, with disparities between ethnic groups and regions. While 20% of women have not had their BP checked in the past year, it is systematically assessed in 98% of pregnant women.

Consequences during and after pregnancy.
Elevations in BP are of particular concern during pregnancy, given the patient's higher risk of developing renal (pre-eclampsia) and cerebral complications with eclampsia crisis, which is an absolute hypertensive emergency. The consequences are equally serious for the child, with significant fetal and perinatal morbidity and mortality. After childbirth, these women have a higher risk of CVD and of remaining hypertensive.

Pregnancy: a window of opportunity for diagnosis
Pregnancy is an important opportunity to identify hypertension and initiate lifelong CVD prevention. The article draws on current US and European recommendations for the diagnosis and management of hypertension during pregnancy. Diagnosis is not fundamentally different, except as regards the search for a cause, which will generally be considered at a later stage, while the management of hypertension during pregnancy indicates the treatments to be used and those contraindicated, to avoid an unfavorable outcome.

Diagnosis and objectives
Hypertension in pregnancy, also in agreement with the American College of Obstetrics and Gynecology (ACOG), is defined as a blood pressure ≥ 140 mm Hg for systolic and/or 90 mm Hg for diastolic before pregnancy or, taking into account that many women only consult their doctor once pregnant, before 20 weeks' gestation or by the use of antihypertensive medication before pregnancy.
It is recommended that blood pressure in women with uncomplicated hypertension be maintained between 120 - 130 and 70 - 80 mm Hg.
Management: lifestyle modification
Lifestyle modifications such as sodium reduction, and weight reduction have been shown to improve blood pressure control in many non-pregnant people. These measures are reasonably advisable for these pregnant women; however, given the need to increase blood volume during pregnancy, strict sodium restriction is not recommended, whereas weight reduction is suggested in overweight/obese women with chronic hypertension prior to pregnancy.
There are physiological changes in blood pressure during pregnancy. In normotensive women entering pregnancy, there is usually a decrease in blood pressure towards the end of the first trimester, secondary to the marked vasodilation that occurs despite the increase in plasma volume that accompanies pregnancy. Blood pressure generally falls by 5 to 10 mm Hg and remains at this lower level throughout pregnancy until the third trimester, when it rises again to pre-pregnancy values. For the majority of women with chronic hypertension, blood pressure changes also follow this same pattern. These physiological changes may mask the diagnosis of chronic hypertension when a woman presents for the first time in the second trimester, after the physiological decrease has occurred. In such cases, the increase in pre-pregnancy values in the third trimester may suggest so-called gestational hypertension. It is when elevated blood pressures persist beyond 12 weeks after delivery that the correct diagnosis of chronic hypertension is recognized.

Management: Antihypertensive drugs.
Because of the fear of affecting placental perfusion through too great a reduction in maternal blood pressure, antihypertensive treatment can and should be reduced in many women.
Unlike non-pregnant hypertensive patients, for whom there are solid data, there are few studies to guide the choice of antihypertensive treatment during pregnancy. Consequently, many of the data on the use of antihypertensives during pregnancy come from literature reviews, "meta-analyses" and small retrospective studies.
The majority of studies compare an antihypertensive to no treatment, and allocation is generally not random.
The Food and Drug Administration (FDA) provides a classification of drugs during pregnancy based on the level of data available to support the absence of harm.
Class A: no fetal risk
Class B: animal studies indicate no fetal risk, but there are no adequate studies in pregnant women.
Class C: animal studies have shown an adverse effect on the fetus, but there are no adequate studies in humans
Class D: evidence of a risk to the human fetus, but the benefits outweigh the disadvantages.
Because of this lack of studies, no antihypertensive is classified in Class A.
Antihypertensives commonly used during pregnancy are classified as class B: α-methyldopa or class C: β-blockers, calcium channel blockers and thiazide diuretics. Angiotensin-converting enzyme (ACE) inhibitors are considered class C in the first trimester and class D in the second and third trimesters.
In contrast to the usual treatment of hypertension, α-methyldopa (ALDOMET) is considered the first-line drug by many guidelines on the basis of the large amount of safety data resulting from its use during pregnancy since the 1960s. No adverse developmental effects have been noted up to the age of 7.5 years. However, α-methyldopa may not be well tolerated by women, due to the common side effect of drowsiness.
Among beta-blockers, labetalol (TRANDATE) is also a first-line treatment for women who need medication during pregnancy.
ACE inhibitors and angiotensin receptor blockers are contraindicated during the second and third trimesters of pregnancy due to adverse effects on the fetus, and there is controversy as to whether ACE inhibitors are safe in the first trimester and are therefore not recommended.
In France, and in Europe, it is also permitted to use Nicardipine, a calcium channel blocker (CRAT.fr website and recommendations from the European and French hypertension societies).

In conclusion:
Pregnancy is an important period for diagnosing HTA in a woman. Although the majority of women with chronic AH can have an unproblematic pregnancy, pregnancies in these women present an increased risk of preeclampsia, fetal growth retardation, early delivery and caesarean section. Women should be informed of these risks before pregnancy and monitored for the potential development of these complications during pregnancy. Thus, pregnancy in hypertensive women needs to be carefully planned and managed through collaboration between obstetricians and hypertension specialists. Once identified, it should be a modifiable target for cardiovascular prevention for the pregnancy itself, to optimize the health of mother and newborn, and throughout life, with regular follow-up for the health of women suffering from hypertension.


Reference:
Cameron N. A.et al : Chronic hypertension in pregnancy: A lens into cardiovascular disease risk and prevention Hypertension. 2023;80:1162-1170.