Hypertension in Pregnancy

Original Editor - Manisha Shrestha Top Contributors - Manisha Shrestha 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.[1]

Hypertension can be further defined as mild, moderate or severe based upon blood pressure level as:

  1. Mild Hypertension: Diastolic blood pressure 90–99mmHg, systolic blood pressure 140–149mmHg.
  2. Moderate Hypertension: Diastolic blood pressure 100–109mmHg, systolic blood pressure 150–159mmHg.
  3. Severe Hypertension: Diastolic blood pressure 110mmHg or greater, systolic blood pressure 160mmHg or greater. For severe hypertension, a repeat measurement should be taken for confirmation no more than 15 minutes later.

Approximately 1% of pregnancies are complicated by pre-existing hypertension, 5–6% by gestational hypertension, and 1–2% by preeclampsia.[1]

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.[2]

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.[3]

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.[4]

[5]

Classification

Hypertensive disorder in pregnancy is classified upon following types based upon complications and period of gestation when it was caused.

Pre-existing (Chronic hypertension of all causes)

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.[3]

  • With comorbid condition(s):

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

  • With evidence of preeclampsia:

This is also known as ‘superimposed preeclampsia’ and is diagnosed when a woman with chronic hypertension or pre-existing proteinuria develops one or more of the systemic features of pre-eclampsia after 20 weeks’ gestation. It may include:

  • Resistant hypertension, or
  • New or worsening proteinuria, or
  • One/more adverse condition(s) or
  • One/more severe complication(s) mentioned below[1]

Gestational (non-proteinuric) hypertension

This is defined as hypertension that develops for the first time at ⩾ 20 weeks of gestation. Gestational hypertension is characterized by the new onset of hypertension after 20 weeks’ gestation without any maternal or fetal features of pre-eclampsia, followed by the return of blood pressure to normal within 3 months post-partum.[3]

The earlier the gestation at presentation and the more severe hypertension, the higher is the likelihood that the woman with gestational hypertension will progress to develop pre-eclampsia or an adverse pregnancy outcome.[3] Gestational hypertension at <34 weeks is associated with a ∼35% risk of preeclampsia.[1]

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 hours 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) mentioned below.

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

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 the 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 ischemia 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.[1]

Other hypertensive effects

  • Transient hypertensive effect: Elevated BP may be due to environmental stimuli or the pain of labor. 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.[1]

Consequences of Hypertensive disorders

For mother

  • Mortality
  • Cesarean section
  • Risk of having hypertension disorders in a subsequent pregnancy.[3]
  • Chronic hypertension[1][3]

For baby

  • Intrauterine growth restriction
  • Oligohydramnios,
  • Placental abruption,
  • Preterm birth
  • NICU stay
  • Perinatal death[6]

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[6][1]

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[6]

Management/Intervention

Medical management

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.

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.

Changes in an antihypertensive agent(s) for care in pregnancy should be made while the woman is planning a pregnancy. 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.

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

A proper diet is very essential. 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.[3]

In a case-control study done in 2018, shows geophagia during pregnancy is not directly associated with pregnancy-induced hypertension(PIH) but is detrimental to maternal health as it contains heavy metals in it. Women with PIH have altered hematology parameters, impaired fasting blood glucose and impaired kidney function, hence, have an increased risk of pregnancy and health complications such as anemia and chronic kidney disease. Pregnant women under study had considerably low intakes of energy and micronutrients which is crucial in the third trimester as fetal demands for nutrients are increased. thus a proper dietary consultation is crucial[7].

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.[3]

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.[6]

Importance of exercise in hypertensive disorders

  • 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.[6]
  • 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.[1]

Obstetric contraindications to exercise

Absolute contraindication:

  • Ruptured membranes.
  • Premature labor.
  • Unexplained persistent vaginal bleeding.
  • Placenta praevia after 28 weeks’ gestation.
  • Pre-eclampsia.
  • Incompetent cervix.
  • Intrauterine growth restriction.
  • High-order multiple pregnancy (eg, triplets).
  • Uncontrolled type I diabetes.
  • Uncontrolled hypertension.
  • Uncontrolled thyroid disease.
  • Other serious cardiovascular, respiratory, or systemic disorders.[8]

Relative contraindication:

  • Recurrent pregnancy loss.
  • Gestational hypertension. (thus need to be individualized and supervised)
  • A history of spontaneous preterm birth.
  • Mild/moderate cardiovascular or respiratory disease.
  • Symptomatic anemia.
  • Malnutrition.
  • Eating disorder.
  • Twin pregnancy after the 28th week.
  • Other significant medical conditions.[8]

Warning Signs to terminate exercises

  • Persistent excessive shortness of breath that does not resolve on rest.
  • Severe chest pain.
  • Regular and painful uterine contractions.
  • Vaginal bleeding.
  • Persistent loss of fluid from the vagina indicating rupture of the membranes.
  • Persistent dizziness or faintness that does not resolve on rest.[8]

Exercise Regime and Evidence

Physical activity

Pregnant women should accumulate at least 150 min of moderate-intensity over three or more days per week to achieve clinically meaningful reductions in pregnancy complications (reductions in the odds of developing gestational diabetes mellitus, pre-eclampsia, and gestational hypertension)[8]

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.[6]

Previously inactive women are encouraged to start physical activity in pregnancy but may need to begin gradually, at a lower intensity and increase the duration and intensity as their pregnancy progresses. [8]  Pregnant women should be encouraged to be physically active, even if they are unable to meet these recommendations. Thus, physical activity regime and exercise regime should be individualized based on concurrent complication, previous activity level, dietary supplements, etc as it affects the dose-response relationship.[8]

Aquatic exercise in Pregnancy
Exercise

In the systematic and meta-analysis[6] study done by Magro-Malosso et al. in 2017 showed that aerobic exercise in singleton pregnancies is associated with a significantly reduced risk of gestational hypertensive disorders. The interventional group with aerobic exercise only without dietary measures showed a 61% reduction in gestational hypertension. They found no difference with regard to preeclampsia between the two groups ( control and intervention). The incidence of cesarean delivery was decreased by 16% in the exercise group. [6]

This study also showed that in low-risk uncomplicated normal-weight singleton gestations, aerobic exercise can be safely performed, as this is not associated with an increased risk of preterm birth or with a reduction in mean gestational age at delivery but is associated with a higher chance of vaginal delivery and a lower rate of CS and gestational diabetes.[6]

Exercise prescription to prevent gestational hypertension and preeclampsia

According to the recent evidence,

  • Frequency: 2-7 times per week
  • Intensity: light to moderate intensity
  • Type: Aerobic exercises ( walking, aquatic exercises)
  • Time: 30-60 minutes[6]

The exercise regime should be individualized.[9]

In pregnant women, the use of ratings of perceived exertion may be a more effective means to monitor exercise intensity during pregnancy than heart-rate parameters. For moderate-intensity exercise, ratings of perceived exertion should be 13–14 (somewhat hard) on the Borg ratings of perceived exertion scale. Using the “talk test” is another way to measure exertion: as long as a woman can carry on a conversation while exercising, she likely is not overexerting herself.[9]

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.

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.[3]

Resources

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Magee LA, Pels A, Helewa M, Rey E, von Dadelszen P. Diagnosis, evaluation, and management of the hypertensive disorders of pregnancy. Pregnancy Hypertension: An International Journal of Women's Cardiovascular Health. 2014 Apr 1;4(2):105-45.
  2. Sadanandan K, Kurian S, Valliot B, Sasidharan A, Sherin N, Madhu R, Ramesh S, Mondain S. PREVALENCE OF GESTATIONAL HYPERTENSION AND FACTORS INFLUENCING SELECTION OF ANTI-HYPERTENSIVE DRUGS IN PREGNANCY. Journal of Hypertension. 2019 Jul 1;37:e239-40.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 CLINICAL PRACTICE GUIDELINE THE MANANGEMENT OF HYPERTENSION IN PREGNANCY. Institute of Obstetricians and Gynaecologists, Royal College of Physicians of Ireland and the Clinical Strategy and Programmes Division, Health Service Executive. Available from: https://rcpi-live-cdn.s3.amazonaws.com/wp-content/uploads/2017/02/Hypertension-Guideline_approved_120716-1.pdf. [Lasted accessed: 28 August, 2020]
  4. Asker SA, Abdelazeim FH, Zaky NA, Wageh A. The effect of maternal exercise program on fetal growth in pre-eclampsia: a prospective, randomized controlled clinical trial. Bulletin of Faculty of Physical Therapy. 2018 Jan 1;23(1):36.
  5. Armando Hasudungan. Pre Eclampsia - Overview (pathophysiology, presentation, treatment). Available from: https://www.youtube.com/watch?v=yta5RRJ-Mg8 [lasted accessed: August 28, 2020]
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 Magro‐Malosso ER, Saccone G, Di Tommaso M, Roman A, Berghella V. Exercise during pregnancy and risk of gestational hypertensive disorders: a systematic review and meta‐analysis. Acta obstetricia et gynecologica Scandinavica. 2017 Aug;96(8):921-31.
  7. Sackey DS, Larbie C, Mensah FO. Geophagia, nutrition and health of women with pregnancy-induced hypertension. African health sciences. 2018;18(4):1243-54.
  8. 8.0 8.1 8.2 8.3 8.4 8.5 Mottola MF, Davenport MH, Ruchat SM, Davies GA, Poitras VJ, Gray CE, Garcia AJ, Barrowman N, Adamo KB, Duggan M, Barakat R. 2019 Canadian guideline for physical activity throughout pregnancy. British Journal of Sports Medicine. 2018 Nov 1;52(21):1339-46.
  9. 9.0 9.1 American College of Obstetricians and Gynecologists. Physical activity and exercise during pregnancy and the postpartum period. Committee Opinion No. 650. Obstet Gynecol. 2015;126(6):e135-142.