Gestational hypertension – Pregnancy Complications
Gestational hypertension formerly known as pregnancy-induced hypertension, refers to hypertension occurring for the first time during pregnancy.
Diagnosis of gestational hypertension requires a blood pressure that is greater than or equal to 140/90 mm Hg. The blood pressure should be elevated on at least two occasions 4–6 hours apart.
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The diagnosis is made after 20 weeks’ gestation and is characterized by a blood pressure that returns to normal by 12 weeks postpartum. Patients with gestational hypertension do not present with proteinuria, which is a characteristic of preeclampsia.
However, gestational hypertension may progress to preeclampsia. If gestational hypertension does not progress to preeclampsia, it is reclassified as transient hypertension. This category includes essential hypertension as well as hypertension secondary to a range of conditions.
Essential hypertension is defined by a blood pressure greater than or equal to 140 mmHg systolic and/or 90 mmHg diastolic confirmed before pregnancy or before 20 completed weeks gestation without a known cause. It may also be diagnosed in women presenting early in pregnancy taking antihypertensive medications where no secondary cause for hypertension has been determined.
Some women with apparent essential hypertension may have white coat hypertension (raised blood pressure in the presence of a clinical attendant but normal blood pressure otherwise as assessed by ambulatory or home blood pressure monitoring).
These women appear to have a lower risk of superimposed preeclampsia than women with true essential hypertension but are still at an increased risk compared with normotensive women. Important secondary causes of chronic hypertension in pregnancy include:
- Chronic kidney disease e.g. glomerulonephritis, reflux nephropathy, and adult polycystic kidney disease
- Renal artery stenosis
- Systemic disease with renal involvement e.g. diabetes mellitus, systemic lupus erythematosus
- Endocrine disorders e.g. phaeochromocytoma, Cushing’s syndrome and primary hyperaldosteronism
- Coarctation of the aorta.
Classifications of Hypertension
|Primary diagnosis||Definition of preeclampsia|
|With comorbid conditions||–|
|With preeclampsia||Resistant hypertension, or|
|(after 20 weeks’ gestation)||New or worsening proteinuria, or One/more adverse condition(s)|
|With comorbid conditions||–|
|With preeclampsia||New proteinuria, or|
|(after 20 weeks’ gestation)||One/more adverse condition(s)|
Blood test abnormalities should be interpreted using pregnancy-specific ranges, some of which are gestation dependent. If features of preeclampsia are present, additional investigations should include:
a) Urinalysis for protein and urine microscopy on a carefully collected mid-stream urine sample.If there is thrombocytopenia or a falling haemoglobin, investigations for disseminated intravascular coagulation and/or haemolysis (coagulation studies, blood film, LDH, fibrinogen) are indicated.
b) Patients with severe, early onset preeclampsia warrant investigation for associated conditions e.g. systemic lupus erythematosus, underlying renal disease or antiphospholipid syndrome. The timing of these investigations will be guided by the clinical features.
c) Although a very rare disorder, undiagnosed phaeochromocytoma in pregnancy is potentially fatal and may present as preeclampsia. In the presence of very labile or severe hypertension measurement of free plasma in fasting condition metanephrines /normetanephrines or 24 hour urinary catecholamines should be undertaken.
d) Amongst women referred for assessment of new onset hypertension, a number will have normal blood pressure and investigations. These women are considered to have transient or labile hypertension. Repeat assessment should be arranged within 3-7 days as some of these women will subsequently develop preeclampsia.
e) Subsequent investigation and management will be based on the results of ongoing blood pressure measurement and these investigations.
Ongoing investigation of women with hypertension in pregnancy
|Chronic hypertension||Assess for proteinuria
If sudden increase in BP or new proteinuria
|Gestational hypertension||Assess for proteinuria
|Preeclampsia||Assess for proteinuria
|At time of diagnosis: if non-proteinuric repeat daily
Twice weekly or more frequent if unstable
Maternal and Fetal Implications
Hypertension in pregnancy places patients and their fetuses at great risk for a variety of complications. Some of the most significant maternal complications of hypertension in pregnancy include cerebral vascular accident (CVA, or stroke), disseminated intravascular coagulation (DIC), and placental abruption from the elevated blood pressure.
Additionally, patients are at risk for the development of HELLP syndrome in the presence of gestational hypertension. Just as its name implies, HELLP syndrome causes great dysfunction within the body and requires immediate intervention. It is characterized by:
- Hemolysis of red blood cells, which leads to anemia
- Elevated liver enzymes leading to epigastric pain
- Low platelets, which cause abnormal bleeding and clotting as well as petechiae
Patients whose function continues to decline without intervention can develop eclampsia and are at risk for cerebral hemorrhage, DIC, and placental abruption. Fetal complications include intrauterine growth retardation and premature delivery resulting from decreased placenta perfusion.
Medical treatment for patients with pregnancy-related hypertension greatly depends on the severity of hypertension and the gestational age of the fetus, as well as the potential risk to the patient and fetus. During early pregnancy, outpatient management is usually appropriate; these patients are monitored at home for blood pressure and proteinuria. Regular fetal monitoring is necessary to evaluate fetal well-being.
In addition, placental perfusion tests can also be performed to assess and monitor uteroplacental sufficiency.
Patients with evidence of severe dysfunction such as seizures, oliguria, renal failure, or HELLP syndrome are usually delivered immediately.Since delivery is the only known cure for pregnancy-related hypertension, many healthcare practitioners will recommend immediate induction and delivery if the patient is near-term and shows signs of severe preeclampsia or eclampsia.
However, if the healthcare practitioner determines that the fetus is too premature for delivery, antihypertensive medications may be administered to decrease blood pressure, thereby prolonging fetal growth in utero.
Glucocorticoids are administered to enhance fetal lung maturity.Healthcare practitioners may prescribe magnesium sulfate (MgSO4) during labor and delivery to prevent seizures.Magnesium sulfate is not used to control hypertension. Magnesium sulfate is administered intravenously via an infusion delivery device during delivery and for 24 hours post delivery.
Since MgSO4 can cause fetal respiratory depression following delivery, arrangements should be made for specialized neonatal care.
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