What is the appropriate management of hypertension diagnosed before 20 weeks gestation in early pregnancy?

Management of Hypertension Diagnosed Before 20 Weeks Gestation

Hypertension presenting before 20 weeks gestation is classified as chronic (pre-existing) hypertension, not gestational hypertension, and requires immediate confirmation, baseline laboratory workup, initiation of antihypertensive therapy if BP ≥140/90 mmHg, and close monitoring throughout pregnancy. 1, 2

Diagnostic Confirmation and Classification

• Confirm the diagnosis immediately using proper blood pressure measurement technique with appropriate cuff size. 2
• If BP ≥160/110 mmHg, confirm within 15 minutes; if BP 140-159/90-109 mmHg, repeat measurements over several hours on the same visit. 2, 3
• This represents chronic hypertension (either essential or secondary), not gestational hypertension, because it presents before the 20-week threshold. 1, 3
• Consider hospital admission for initial assessment to confirm diagnosis and rule out severe features. 2

Immediate Laboratory Investigations

Obtain the following baseline tests immediately to establish a reference for detecting superimposed preeclampsia later: 2, 3

• Complete blood count with hemoglobin and platelet count
• Liver transaminases (AST, ALT)
• Serum creatinine and electrolytes
• Serum uric acid
• Urinalysis with proteinuria assessment (24-hour urine collection or spot urine protein-to-creatinine ratio)

Note: Proteinuria ≥0.3 g/24 hours or ≥30 mg/mmol on spot urine indicates superimposed preeclampsia, though this is uncommon before 20 weeks. 2

Blood Pressure Treatment Thresholds and Targets

• Initiate antihypertensive medication if BP is persistently ≥140/90 mmHg. 2
• Target BP should be 110-140/85 mmHg to reduce severe hypertension risk without compromising uteroplacental perfusion. 2
• For BP in the 140-150/90-99 mmHg range, consider initial non-pharmacological management with close supervision, though pharmacologic therapy is generally preferred at ≥140/90 mmHg. 2

First-Line Antihypertensive Medications

Preferred agents: 2

• Methyldopa (longest safety data with 7.5 years of infant follow-up)
• Labetalol (most commonly used in the UK, available orally and intravenously) 4
• Nifedipine (calcium channel blocker with extensive pregnancy data)

Absolutely contraindicated: ACE inhibitors, ARBs, and direct renin inhibitors due to severe fetotoxicity, particularly in second and third trimesters. 2

Non-Pharmacological Management

For BP 140-150/90-99 mmHg with close supervision: 2

• Limitation of activities with some bed rest in left lateral position
• Normal diet without salt restriction
• Calcium supplementation of at least 1 gram daily (especially if dietary calcium intake is low)
• Do not recommend weight reduction during pregnancy in obese women, as it can reduce neonatal weight and slow infant growth. 2

Aspirin Prophylaxis: Critical Timing Issue

Low-dose aspirin (75-100 mg/day) should have been started before 16 weeks gestation in women with chronic hypertension or history of early-onset preeclampsia (<28 weeks). 2, 5

• At 17-20 weeks, this window has likely passed, but discuss with the patient whether aspirin was initiated earlier.
• If not started by 16 weeks, the benefit is significantly reduced. 2

Monitoring Protocol Throughout Pregnancy

• Frequent BP monitoring with close supervision throughout pregnancy. 2
• Consider home BP monitoring using devices validated specifically for pregnancy. 1, 3
• Fetal ultrasound for biometry should begin at 26 weeks if maternal uric acid is elevated or preeclampsia develops, with repeat every 2-4 weeks if normal. 2
• Doppler ultrasound of uterine arteries after 20 weeks helps detect higher risk of gestational hypertension, preeclampsia, and intrauterine growth retardation. 1

Red Flags Requiring Immediate Hospital Assessment

Admit immediately if any of the following develop: 2

• BP ≥160/110 mmHg
• Development of proteinuria
• Severe headache, visual disturbances, or neurological symptoms
• Laboratory abnormalities suggesting preeclampsia (thrombocytopenia, elevated liver enzymes, rising creatinine)

Management of Severe Hypertension (≥160/110 mmHg)

• Initiate urgent treatment within 15 minutes to 1 hour to prevent hemorrhagic stroke. 2, 4
• Target BP of 140-150/90-100 mmHg (not normotension). 2
• Use IV labetalol, oral nifedipine, or IV hydralazine based on availability and clinician experience. 2, 4

Delivery Timing

Without preeclampsia: 2

• Delivery can be delayed until 39+6 weeks if BP remains controlled, fetal monitoring is reassuring, and preeclampsia has not developed.

With superimposed preeclampsia: 2

• Deliver at ≥37 weeks for preeclampsia at term
• Earlier delivery indicated for: severe hypertension despite multiple agents, progressive thrombocytopenia, progressively abnormal liver/renal tests, pulmonary edema, severe neurological features, or non-reassuring fetal status

Prognosis and Long-Term Implications

• Women with chronic hypertension face increased risk of preeclampsia (34.9-44.2%), placental abruption, preterm birth, fetal growth restriction, and cesarean delivery. 6, 7
• Newly diagnosed chronic hypertension in early pregnancy (vs. pre-pregnancy diagnosis) carries 1.8-fold higher risk of preterm preeclampsia, emphasizing the need for intense monitoring. 6
• All women with hypertensive disorders in pregnancy require annual cardiovascular risk assessment lifelong. 3