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Incidence of Hypertension in pregnancy (HP)
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Incidence of Hypertension in pregnancy (HP)
Hypertensive disorders of pregnancy affect about 10% of all pregnant women around the world. Although the incidence varies from region to region, eclampsia accounts for up to forty percent of maternal mortality in some countries. The incidence of pre-eclampsia ranges from 3% to 7% for nulliparas and 1% to 3% for multiparas. Pre-eclampsia is a major cause of maternal mortality and morbidity, preterm birth, perinatal death, and intrauterine growth restriction.
Classification of HP
There has never been a definite consensus on the classification and diagnostic criteria for the hypertensive disorders of pregnancy.
Most often, hypertensive disorders during pregnancy are classified into 4 categories:
· Gestational hypertension.
· Preeclampsia and eclampsia syndrome
· Preeclampsia syndrome superimposed on chronic hypertension
· Chronic hypertension
Definitions of HP
The use of the following definitions is recommended
Gestational hypertension:
• New onset of hypertension arising after 20 weeks gestation
• No additional features of preeclampsia
• Resolves within 3 months postpartum
Moderate and severe gestational hypertensions are distinguished.
Moderate hypertension:
• sBP 141 mmHg to 159 mmHg and/ or
• dBP 91 mmHg to 109 mmHg.
Severe hypertension:
• sBP greater than or equal to 160 mmHg and/or
• dBP greater than or equal to 110 mmHg
Preeclampsia: Preeclampsia is defined as the presence of (1) a systolic blood pressure (sBP) greater than or equal to 140 mm Hg or a diastolic blood pressure (dBP) greater than or equal to 90 mm Hg or higher, on two occasions at least 4 hours apart in a previously normotensive patient, or (2) an sBP greater than or equal to 160 mm Hg or a dBP greater than or equal to 110 mm Hg or higher (In this case, hypertension can be confirmed within minutes to facilitate timely antihypertensive therapy. ). Preeclampsia is a multi-system, progressive disorder characterized by the new onset of hypertension and proteinuria or hypertension and end-organ dysfunction with or without proteinuria (and/or non-dependent edema) in the last half of pregnancy ( after 20th week ). Thus, preeclampsia is diagnosed by hypertension and the coexistence of one or more of the following new-onset conditions:
1. Proteinuria
2. Other maternal organ dysfunction:
• renal insufficiency (creatinine > 90 umol/L)
• liver involvement (elevated transaminases and/or severe right upper quadrant or epigastric pain)
• neurological complications (examples include eclampsia, altered mental status, blindness, stroke, or more commonly hyperreflexia when accompanied by clonus, severe headaches when accompanied by hyperreflexia, persistent visual scotomata)
• haematological complications (thrombocytopenia, DIC, haemolysis)
3. Uteroplacental dysfunction:
• fetal growth restriction
Eclampsia - clinical presentation of seizure, convulsion, or altered mental status in the setting of the signs and symptoms of preeclampsia.
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Preeclampsia superimposed on chronic hypertension: development of pre-eclampsia (or eclampsia) in pre-existing hypertension detected by a further increase of 30 mmHg or more in systolic blood pressure or 15 mmHg or more in diastolic blood pressure, and the development of proteinuria or edema, or both.
HELLP syndrome, chronic gestational hypertension, unclassified hypertensionare also distinguished.
HELLP syndrome: the association of Haemolysis, Elevated Liver enzymes and Low Platelet count. Presents the most severe form of the disease.
Unclassified hypertension and/or proteinuria: Hypertension and/or proteinuria found either (a) first visit after 20 weeks of pregnancy (in a woman without known chronic hypertension or renal disease); or (b) during pregnancy, labor or the puerperium where information is insufficient to permit classification.
Chronic gestational hypertension is hypertension that occurs after the 20th week of pregnancy and persists even after the 12th week after childbirth.
Diagnostics of hypertension in pregnancy
Any hypertension during pregnancy should be evaluated according to diastolic blood pressure (dBP). dBP represents peripheral resistance of blood vessels, blood supply property and does not depend on emotional factors, unlike systolic blood pressure(sBP). Hypertension in pregnancy should be defined as a dBP of 90 mmHg, based on the average of at least two measurements, taken using the same arm. Women with a sBP of 140 mmHg should be followed closely for development of diastolic hypertension.
Diagnostics of proteinuria
All pregnant women should be assessed for proteinuria. Urinary dipstick testing may be used for screening for proteinuria when the suspicion of preeclampsia is low. More definitive testing for proteinuria (by urinary protein: creatinine ratio or 24-hour urine collection) is encouraged when there is a suspicion of preeclampsia, including in hypertensive pregnant women with rising BP or in normotensive pregnant women with symptoms or signs suggestive of preeclampsia. Proteinuria should be strongly suspected when urinary dipstick proteinuria is 2+. Proteinuria should be defined as 0. 3g/d in a 24-hour urine collection or 30 mg/mmol urinary creatinine in a spot (random) urine sample.
It should be noted, that ISSHP (International Society for the Study of Hypertension in Pregnancy) revised classification of pregnancy hypertension at 2014 year. The ISSHP revised classification for hypertensive disorders in pregnancy is as follows:
1. Chronic hypertension.
2. Gestational hypertension.
3. Pre-eclampsia – de novo or superimposed on chronic hypertension.
4. White coat hypertension.
The term “white coat” comes from references to the white coats traditionally worn by doctors. The white coat effect means that patient’s blood pressure is higher when it is taken in a medical setting than it is when taken at home. On average, when blood pressure is taken at home the top (systolic) number can be around 10mmHg lower than it would be if taken by a doctor and 5mmHg lower on the diastolic number. For some people this difference can be even greater. Isolated office (white coat) hypertension should be defined as office diastolic BP of 90 mmHg, but home BP of < 135/85 mmHg.
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Risk factors for HP
Risk factors for preeclampsia and their odds ratios are as follows:
• Nulliparity (3. 1)
• Age > 40 years (3: 1)
• Black race (1. 5: 1)
• Family history (5: 1)
• Obesity (3: 1)
• Chronic renal disease (20: 1)
• Chronic hypertension (10: 1)
• Antiphospholipid syndrome (10: 1)
• Diabetes mellitus (2: 1)
• Twin gestation (but unaffected by zygosity) (4: 1)
• High body mass index (3: 1)
• Homozygosity for angiotensinogen gene T235 (20: 1)
• Heterozygosity for angiotensinogen gene T235 (4: 1)
Some other signs are also noted as risk factors for preeclampsia:
• Previous history of preeclampsia
• sBP greater than or equal to 130 mmHg at booking
• dBP greater than or equal to 80 mmHg at booking
• Inter-pregnancy interval greater than 10 years
• Antiphospholipid antibodies
• Chronic autoimmune disease
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