At what gestational age is the highest chance for preeclampsia?

Highest Risk Period for Preeclampsia

Preeclampsia is most common at term (≥37 weeks' gestation), while the most severe complications typically occur when preeclampsia develops before 32 weeks' gestation. 1

Timing of Preeclampsia Onset

• Preeclampsia can occur any time from 20 weeks' gestation until the postpartum period 2
• By definition, preeclampsia cannot be diagnosed before 20 weeks' gestation 1
• Serious morbidity associated with preeclampsia can occur from 20 weeks' gestation to after delivery 1
• Eclampsia (seizures) is most common at term 1
• Severe complications like placental abruption, HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), and renal failure are more common before 32 weeks' gestation 1

Severity Based on Gestational Age

• Preeclampsia with onset before 32 weeks has the most serious outcomes 1
• The interval between diagnosis and delivery for early-onset preeclampsia is on average 14 days (range 0-62 days) 1
• A substantial number of women with early-onset preeclampsia require delivery within 72 hours of diagnosis 1
• Preeclampsia is classified as:
  • Preterm (delivery <37 weeks' gestation) 2
  • Term (delivery ≥37 weeks' gestation) 2
  • Postpartum preeclampsia 2

Management Based on Gestational Age

• For preeclampsia at ≥37 weeks' gestation: immediate delivery is recommended regardless of severity 3
• For preeclampsia between 34-37 weeks' gestation without severe features: expectant management with close monitoring 3
• For preeclampsia at <34 weeks' gestation with stable maternal and fetal conditions: conservative management with close monitoring 3
• For preeclampsia at <24 weeks' gestation: counseling about possible pregnancy termination due to high maternal risks and poor fetal outcomes 3, 4

Risk Factors for Preeclampsia

• First pregnancy (nulliparity) increases risk 2.91 times 1
• Previous preeclampsia increases risk 7.19 times 1
• Presence of antiphospholipid antibodies increases risk 9.72 times 1
• Pre-existing diabetes increases risk 3.56 times 1
• Multiple pregnancy increases risk 2.93 times 1
• Family history of preeclampsia increases risk 2.90 times 1
• Advanced maternal age (≥40 years) increases risk 1.68-1.96 times 1
• High BMI at booking increases risk 1.55 times 1

Clinical Implications

• Women with preeclampsia onset before 32 weeks require more intensive monitoring 1
• Before 32 weeks, women with risk factors should be seen at least once every three weeks 1
• After 32 weeks until delivery, these women should be seen at least once every two weeks 1
• Preeclampsia can progress to a life-threatening situation in approximately two weeks from diagnosis 1
• All women should be educated about symptoms of preeclampsia and how to contact healthcare professionals at all times 1

Pitfalls and Caveats

• Preeclampsia should not be classified as mild versus severe clinically, as all cases may rapidly progress to emergencies 3
• Blood pressure alone is not a reliable way to stratify immediate risk, as serious organ dysfunction can develop at relatively mild levels of hypertension 3
• Serum uric acid and proteinuria levels should not be used as indications for delivery 3
• Absence of antenatal care is strongly associated with eclampsia and fetal death 1
• Women with no risk factors can still develop preeclampsia and should be monitored according to standard protocols 1