What are the Carpenter criteria for diagnosing and managing pregnancy-induced hypertension (PIH) in pregnant women?

Carpenter Criteria for Diagnosing and Managing Pregnancy-Induced Hypertension (PIH)

The Carpenter criteria are not specifically mentioned in the current hypertensive disorders of pregnancy guidelines. Instead, the International Society for the Study of Hypertension in Pregnancy (ISSHP) classification system is the most widely accepted standard for diagnosing and managing pregnancy-induced hypertension.

Classification of Hypertensive Disorders in Pregnancy

• Hypertension in pregnancy is defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg, with severe hypertension defined as ≥160/110 mmHg 1, 2
• Hypertensive disorders in pregnancy are classified into four main categories 1, 3:
  • Pre-existing (chronic) hypertension: Present before pregnancy or develops before 20 weeks gestation
  • Gestational hypertension: New-onset hypertension after 20 weeks without proteinuria
  • Preeclampsia: Gestational hypertension with proteinuria or other maternal organ dysfunction
  • Pre-existing hypertension with superimposed preeclampsia

Diagnostic Criteria for Preeclampsia

• Preeclampsia is diagnosed when gestational hypertension is accompanied by ≥1 of the following new-onset conditions at or after 20 weeks' gestation 1, 2:

  • Proteinuria (≥0.3 g/day in 24h collection or ≥30 mg/mmol urinary creatinine ratio)
  • Renal insufficiency (serum creatinine >90 μmol/L)
  • Liver involvement (elevated transaminases, severe right upper quadrant pain)
  • Neurological complications (severe headache, visual disturbances, eclampsia)
  • Hematological complications (thrombocytopenia, hemolysis, DIC)
  • Uteroplacental dysfunction (fetal growth restriction)

• Severe features of preeclampsia include 1:

  • Right upper quadrant/epigastric pain due to liver edema
  • Headache with visual disturbances (cerebral edema)
  • Hyperreflexia with clonus
  • Convulsions
  • HELLP syndrome (hemolysis, elevated liver enzymes, low platelet count)

Blood Pressure Measurement and Confirmation

• Diagnosis should be based on at least two high BP readings on two separate occasions 3
• For severe hypertension (≥160/110 mmHg), confirmation should be done within 15 minutes 1, 3
• For less severe hypertension, confirmation requires repeated readings over several hours 1
• 24-hour ambulatory BP monitoring may be useful for diagnosis, particularly in high-risk pregnant women 3

Proteinuria Assessment

• Proteinuria should be initially assessed by automated dipstick urinalysis 1, 3
• Significant proteinuria is defined as ≥0.3 g/day in a 24h urine collection or ≥30 mg/mmol urinary creatinine in a spot random urine sample 1, 3

Management Recommendations

• Urgent treatment of severe hypertension (>160/110 mmHg) in a monitored setting with 1:

  • Oral nifedipine
  • Intravenous labetalol
  • Intravenous hydralazine
  • Oral labetalol if other treatments unavailable

• For non-severe hypertension (≥140/90 mmHg) 1:

  • Target diastolic BP of 85 mmHg (systolic BP 110-140 mmHg)
  • Reduce or cease antihypertensives if diastolic BP falls <80 mmHg
  • First-line agents: oral methyldopa, labetalol, oxprenolol, nifedipine
  • Second/third-line agents: hydralazine, prazosin

• Magnesium sulfate prophylaxis for women with preeclampsia who have 1:

  • Proteinuria with severe hypertension
  • Hypertension with neurological signs or symptoms

• Delivery indications in preeclampsia 1:

  • Reaching 37 weeks' gestation
  • Uncontrolled severe hypertension despite three antihypertensive agents
  • Progressive thrombocytopenia
  • Abnormal liver or renal function tests
  • Pulmonary edema
  • Neurological complications
  • Non-reassuring fetal status

Monitoring Recommendations

• Initial hospital assessment for all women with newly diagnosed preeclampsia 1

• Maternal monitoring should include 1:

  • Regular BP monitoring
  • Assessment for proteinuria if not already present
  • Clinical assessment including clonus
  • Blood tests at least twice weekly: hemoglobin, platelet count, liver enzymes, renal function, uric acid

• Fetal monitoring should include 1:

  • Initial assessment of fetal well-being
  • Serial ultrasound for fetal growth, amniotic fluid, and umbilical artery Doppler
  • More frequent monitoring if fetal growth restriction is present

Important Clinical Notes

• Transient gestational hypertension carries a 40% risk of developing gestational hypertension or preeclampsia later in pregnancy 2
• Women with unknown BP before 20 weeks should be managed as if they have gestational hypertension or preeclampsia 2
• The level of BP itself is not a reliable way to stratify immediate risk in preeclampsia, as serious organ dysfunction can occur at relatively mild levels of hypertension 1