Hypertension in Pregnancy

Original Editor - Manisha Shrestha Top Contributors - Manisha Shrestha, Kirenga Bamurange Liliane, Nupur Smit Shah, Lucinda hampton and Kim Jackson

Original Editor - User Name

Top Contributors - Manisha Shrestha, Kirenga Bamurange Liliane, Nupur Smit Shah, Lucinda hampton and Kim Jackson  

Introduction

Hypertensive disorders of pregnancy are a leading cause of maternal and neonatal morbidity and mortality. Hypertension in pregnancy should be defined as a hospital systolic blood pressure (SBP) ⩾ 140 mmHg and/or diastolic blood pressure (DBP) ⩾ 90 mmHg, based on the average of at least two measurements, taken at least 15 min apart, using the same arm.

Hypertensive disorders during pregnancy may result in substantial short-term maternal morbidity ranging from 10-15% worldwide whereas chronic hypertension and an increase in lifetime cardiovascular risk as to the long-term consequences.

Hypertensive disorders also carry a risk for the baby. About 1 in 20 (5%) stillbirths in infants without congenital abnormality occur in women with preeclampsia. 8–10% of all preterm births result from hypertensive disorders. Small-for-gestational-age (SGA) babies (mainly because of intrauterine growth restriction (IUGR) arising from placental disease) are common, with 20–25% of preterm births and 14–19% of term births in women with pre-eclampsia being less than the tenth centile of birthweight for gestation.

Pathogenesis

The exact pathogenesis of hypertensive disorder mainly pre-eclampsia is unknown. But several factors have been identified in pre-eclampsia and they are:

1. Vasoconstriction causing hypertension
2. Platelets activation with intravascular coagulation
3. Endothelial dysfunction causing edema
4. Maternal plasma volume contraction

Thus preeclampsia results from a mismatch between uteroplacental supply and fetal demands, leading to its systemic inflammatory maternal (and fetal) manifestations. There is a decrease in blood flow in the uteroplacental due to vascular endothelial malfunction and vasospasm. So, the main impact on the fetus is undernutrition as a result of uteroplacental vascular insufficiency, which leads to growth retardation. So the most common consequences associated with pre-eclampsia is a restriction of intrauterine growth, low birth weight, and prematurity.

Classification

A. Pre-existing (chronic hypertension)

This is defined as hypertension that was present either pre-pregnancy or that develops at <20 weeks of gestation. A substantial number of pregnancies (0.2– 5%) are complicated by pre-existing hypertension and the prevalence in western societies is likely to increase due to the advancing age of the prospective mother at conception and the rising tide of obesity. Chronic hypertension of all causes can be divided into essential and secondary hypertension based upon its causes.

• With comorbid condition(s):

Comorbid conditions (e.g., pre-gestational type I or II diabetes mellitus or kidney disease) warrant tighter BP control outside of pregnancy because of their association with heightened cardiovascular risk.

• With evidence of preeclampsia:

This is also known as ‘superimposed preeclampsia’ and is defined by the development of one or more of the following at ⩾ 20 weeks:

• Resistant hypertension, or
• New or worsening proteinuria, or
• One/more adverse condition(s) or
• One/more severe complication(s)

B. Gestational hypertension

This is defined as hypertension that develops for the first time at ⩾ 20 weeks of gestation.

• With comorbid condition(s): Comorbid conditions (e.g., pregestational type I or II diabetes mellitus or kidney disease) warrant tighter BP control outside of pregnancy because of their association with heightened cardiovascular risk.

• With evidence of preeclampsia: Evidence of preeclampsia may appear many weeks after the onset of gestational hypertension.

C. Pre-eclampsia

Pre-eclampsia is defined as the presence of a systolic blood pressure greater than or equal to 140 mmHg or diastolic blood pressure greater than or equal to 90 mmHg or higher, on two occasions at least 4 h apart in a previously normotensive patient along with proteinuria. Preeclampsia is defined by gestational hypertension and one or more of the following:

• New proteinuria(of greater than or equal to 0.3 g in a 24-h urine specimen), or
• One/more adverse conditions, or
• One/more severe complication(s)

Severe preeclampsia is defined as preeclampsia with one or more severe complication(s). Severe pre-eclampsia is associated with different degrees of fetal injury.

D. Other hypertensive effects

• Transient hypertensive effect: Elevated BP may be due to environmental stimuli or the pain of labour. A transient hypertensive effect is not associated with an increased risk of adverse outcomes.
• White-coat hypertensive effect: BP that is elevated in the office i.e in the presence of a clinical attendant (SBP ⩾ 140 mmHg or dBP ⩾ 90 mmHg) but is consistently normal outside of the office (<135/85 mmHg) by ambulatory BP monitoring (ABPM) or home BP monitoring(HBPM). These women appear to have a lower risk of superimposed pre-eclampsia than women with true essential hypertension. The white-coat effect in early pregnancy is common. Forty percent of women progress to persistent hypertension at ≥ 20 weeks (i.e., gestational hypertension) and 8% to pre-eclampsia. Women with white-coat effects have risks (e.g., severe hypertension, preterm delivery, and NICU admission) intermediate between normotension and either chronic or gestational hypertension.
• Masked hypertensive effect: BP that is consistently normal in the office (SBP < 140 mmHg or dBP < 90 mmHg) but is elevated outside of the office (⩾135/85 mmHg) by ABPM or repeated HBPM.

Adverse conditions and severe complications of preeclampsia.

Adverse conditions consist of maternal symptoms, signs, and abnormal laboratory results, and abnormal fetal monitoring results that may herald the development of severe maternal or fetal complications.

Organ system affected	Adverse conditions (that increase the risk of severe complications)	Severe complications (that warrant delivery)
CNS	Headache/visual symptoms	Eclampsia PRES Cortical blindness or retinal detachment Glasgow coma scale < 13 Stroke, TIA, or RIND
Cardiorespiratory	Chest pain/dyspnoea Oxygen saturation < 97%	Uncontrolled severe hypertension (over a period of 12hr despite use of three antihypertensive agents), Oxygen saturation < 90%, need for ⩾ 50% oxygen for > 1hr, intubation (other than for Caesarean section), pulmonary oedema Positive inotropic support Myocardial ischaemia or infarction
Haematological	Elevated WBC count Elevated INR or aPTT  Low platelet count	Platelet count < 50x109/L Transfusion of any blood product
Renal	Elevated serum creatinine  Elevated serum uric acid	Acute kidney injury (creatinine > 150 μM with no prior renal diseases New indication for dialysis
Hepatic	Nausea or vomiting RUQ or epigastric pain Elevated serum AST, ALT, LDH, or bilirubin Low plasma albumin	Hepatic dysfunction (INR > 2 in absence of DIC or warfarin) Hepatic haematoma or rupture
Feto-placental	Non-reassuring FHR IUGR  Oligohydramnios Absent or reversed end-diastolic flow by Doppler velocimetry	Non-reassuring FHR IUGR Oligohydramnios Absent or reversed end-diastolic flow by Doppler velocimetry

ST, aspartate aminotransferase; ALT, alanine aminotransferase; DIC, disseminated intravascular coagulation; FHR, fetal heart rate; LDH, lactate dehydrogenase; PRES, posterior reversible leukoencephalopathy syndrome; RIND, reversible neurological deficit < 48hr; RUQ, right upper quadrant; TIA, transient ischaemic attack.

Consequences of Hypertensive disorders

For mother

For baby

• Intrauterine growth restriction
• Oligohydramnios,
• Placental abruption,
• Preterm birth
• Perinatal death

Risk factors

Women at high risk of having pre-eclampsia are those with any of the following:

• Hypertensive disease during a previous pregnancy
• Chronic kidney disease
• Autoimmune diseases such as systemic lupus erythematosus or antiphospholipid syndrome
• Inherited or acquired thrombophilia
• Type 1 or type 2 diabetes
• Chronic hypertension

Factors indicating moderate risk are:

• First pregnancy (Nulliparity)
• Age 40 years or older (advanced maternal age).
• Pregnancy interval of more than 10 years
• Body mass index (BMI) of 35kg/m2 or more at the first visit (obesity or excessive weight gain in pregnancy)
• Family history of pre-eclampsia
• Multiple pregnancy

Management/Intervention

Medical management

Preconception Care

Pre-conceptual counseling for women with pre-existing hypertension is recommended. Maternal characteristics that increase the risk of superimposed pre-eclampsia should be identified and modifiable risk factors such as obesity and poorly controlled diabetes should be addressed. Counseling should include an explanation of the risk of pre-eclampsia and fetal growth restriction. Women should be educated about the signs and symptoms of pre-eclampsia. Changes in an antihypertensive agent(s) for care in pregnancy should be made while the woman is planning pregnancy if the woman has uncomplicated preexisting hypertension, or, if in the presence of comorbid conditions, she is likely to conceive easily (within 12 months). Angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARB) and renin inhibitors should be discontinued when planning a pregnancy or as soon as pregnancy is diagnosed.

Reducing the Risk of Hypertensive Disorders in Pregnancy

Strategies to prevent pre-eclampsia are the subject of on-going intensive research efforts and no treatment can effectively prevent pre-eclampsia in all cases.

Daily use of low-dose aspirin (LDA) appears to reduce the risk of pre-eclampsia in women at increased risk of developing the condition. Therefore, women at high risk of pre-eclampsia should take 75mg of aspirin daily from 12 weeks until the birth of the baby.

Dietary Counseling

Calcium supplementation appears to reduce the risk of hypertension and/or preeclampsia, though this effect seems to be strongest in women whose dietary calcium intake is low and/or who are at increased risk of pre-eclampsia. Women with calcium intake <1000 mg/day may consider increasing their daily calcium intake to 1000 – 2500 mg/day by consuming additional foods high in calcium (i.e. dairy products or fortified soy beverages) or through supplementation.

Physiotherapy intervention

Advice on rest, exercise, and work for women at risk of hypertensive disorders during pregnancy should be the same as for healthy pregnant women.

Perinatal exercise has been recommended as strategies to prevent and/or decrease pre-eclampsia complications for both mother and the fetus especially when performed under professional guidance and supervision. A recent randomized controlled trial (RCT) showed that maternal exercise may be a preventative tool for hypertension.

Importance of exercise

• Exercise promotes placental growth and maternal angiogenic balance.
• Several reports also showed that exercise positively influences fetal growth and later developmental milestones in addition to the fetoplacental effect of exercise.
• Exercise in pregnancy, reducing oxidative stress, may improve endothelial function and could theoretically reduce the risk of preeclampsia.
• Intermittent reduction in fetal and placental oxygen supplies as a result of pre-eclampsia is believed to be the stimulus for exercise-induced increases in placental growth and vascularity.
• The adoption of a supervised, low-to-moderate intensity strength training program during pregnancy can be safe and efficacious for pregnant women

obstetric contraindications to exercise,

mostly as recommended by the American Congress of

Obstetricians and Gynecologists (ACOG)

intervention group participated in

planned aerobic exercise and diet and physical activity.E xercise initiated at

13 weeks and at 20 weeks, in the intervention group. aerobic

exercise consisting of walking session, light-intensity to

moderate-intensity exercise or aquatic exercise for 45 mins in average. physical activity was recommended daily with out specific duration. Pregnant women who

were randomized in early pregnancy to approximately

30–60 min of aerobic exercise two to seven times per

week until at least week 35 or up to delivery had a signif-

icant lower incidence of gestational hypertensive disor-

ders,

Performing an analysis

for an exercise dose effect was not feasible, given the lack

of individual level patient data. defined as gestational hypertension or preeclamps

Women in the exercise group

had a significantly lower rate of cesarean delivery com-

pared with women in the control group (RR 0.84, 95%

CI 0.73–0.98).

The incidence of cesarean delivery was decreased by

16% in the exercise group. The subgroup analysis for aer-

obic exercise only, in which no dietary measures were

included, confirmed a significant 61% decrease in gesta-

tional hypertensive disorders.

physical activity: Wolf et al. (28) including 11 studies evaluated leisure

time physical activity and the risk of preeclampsia, but no

RCTs were included (28). They found that high intensity

leisure time physical activity before or during pregnancy

or more than four hours per week of leisure time physical

activity may reduce the risk of preeclampsia

We also assessed the following post hoc secondary out-

comes: cesarean delivery, gestational age at delivery, and

neonatal outcomes including birthweight, and Apgar

score at one and at five minutes.

Postnatal management

Care in the first 6 Weeks Postpartum

Blood pressure usually stabilizes in the first two months following pregnancy. Anti-hypertensive medication may require for maintenance. Antihypertensive agents generally acceptable for use in breastfeeding include the following: labetalol, nifedipine XL, methyldopa, captopril, and enalapril.

Care beyond 6 weeks postpartum

Follow-up after 6 weeks is required to ensure the resolution of pregnancy-related changes and ascertain the need for ongoing care. Advice regarding future lifestyle and optimization of risk factors in subsequent pregnancies may be required. This is particularly relevant for women who are obese, have cardiovascular risk factors, secondary hypertension, or end-organ disease.

Long term consequences

Women who have been diagnosed with either pre-eclampsia or gestational hypertension are at increased risk of subsequent hypertension and cardiovascular disease. So counseling patients about annual blood pressure checks and regular assessment of other cardiovascular risk factors including serum lipids and blood glucose is necessary. Avoiding smoking, maintaining a healthy weight, exercising regularly, and eating a healthy diet is crucial.

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