What are the guidelines for ultrafiltration (UF) dialysis in pregnancy?

Guidelines for Ultrafiltration Dialysis in Pregnancy

Pregnant women with end-stage kidney disease should receive long frequent hemodialysis either in-center or at home, with intensive ultrafiltration management to optimize maternal and fetal outcomes. 1

Dialysis Prescription Recommendations

• Provide intensive hemodialysis with at least 6 sessions per week, totaling 36-48 hours weekly for pregnant women with end-stage kidney disease 2, 1
• A clear dose-response relationship exists between dialysis intensity and pregnancy outcomes:
  • ≤20 hours/week: 48% live birth rate
  • 30 hours/week: 75% live birth rate

  • 36 hours/week: 85% live birth rate 2, 1

• Standard adequacy targets (spKt/V 1.4 per session) are insufficient for pregnant women; aim for a higher clearance with a standard Kt/V of at least 2.3 volumes per week 2, 1

Ultrafiltration Management

• Maintain ultrafiltration rates below 8 mL/h/kg during hemodialysis sessions to prevent harmful effects on placental-fetal blood flow 3
• Safe ultrafiltration rates of approximately 1.4 ± 0.4 L (<6 mL/h/kg) per HD session have been demonstrated without chronic fetal deleterious effects 3
• Monitor placental and fetal blood flow using obstetric Doppler ultrasonography, which is a simple and non-invasive method to determine safe ultrafiltration rates during pregnancy 3
• Carefully assess fluid status to prevent both dehydration and fluid overload, as both conditions can compromise placental perfusion 2, 4

Technical Considerations

• Use biocompatible dialysis membranes for all pregnant women on hemodialysis 2, 1
• Closely monitor vital signs, particularly blood pressure, to avoid intradialytic hypotension which can lead to placental ischemic injury and fetal distress 2, 3
• Target pre-dialysis BUN levels below 35 mg/dL to improve pregnancy outcomes 2, 4
• Monitor electrolytes carefully, as intensive dialysis may lead to excessive removal of phosphorus and potassium 5
• Target serum bicarbonate levels of 18-20 mEq/L during pregnancy 5

Expected Outcomes

• With intensive hemodialysis (>36 hours/week) and BUN <35 mg/dL:
  • Live birth rates can reach 85-89%
  • Mean gestational age of 36 weeks
  • Higher mean birth weight (>2000g) 2, 1
• Without intensive dialysis, only about 50% of pregnancies in dialysis patients result in surviving infants 4, 5

Common Pitfalls and Considerations

• Inadequate dialysis intensity is a major pitfall - conventional thrice-weekly dialysis is insufficient for pregnant women 2, 4
• Hypertension is the greatest danger to the mother and requires extreme vigilance up to six weeks postpartum 5
• Increased doses of erythropoietin are needed to meet the demands for increased red cell production during pregnancy 5
• Increased supplementation of water-soluble vitamins, particularly folate, is required 5
• Prematurity remains a significant challenge, with over 80% of live-born infants being premature 5

Monitoring Recommendations

• Regular assessment of fluid status through clinical examination at each dialysis session 2, 4
• Weekly monitoring of pre-dialysis BUN, electrolytes, and acid-base status 4, 5
• Regular obstetric ultrasound to monitor fetal growth and development 4
• Consider regular obstetric Doppler ultrasonography to assess placental-fetal blood flow, especially when adjusting ultrafiltration rates 3

By following these intensive dialysis and careful ultrafiltration management guidelines, the chances of a successful pregnancy outcome in women with end-stage kidney disease can be significantly improved, though pregnancy in dialysis patients remains a high-risk undertaking requiring close multidisciplinary collaboration 6, 4.