Navigating pregnancy with maternal antibodies can feel overwhelming, but having a clear plan can make all the difference. This week-by-week guide breaks down the typical care timeline for alloimmunized pregnancies, helping you and your care team stay informed, proactive, and prepared every step of the way.

Before or Early Pregnancy

• Get an antibody screen and titer
• Identify antibody or antibodies present
• Determine titer level
• Confirm accurate due date
• Test the baby’s father for antigen status
• If there was a previously affected pregnancy or high antibody levels, discuss starting IVIG and plasmapheresis between 10–12 weeks

Weeks 10–12

• Continue titer monitoring every 4 weeks if the baby is or may be antigen-positive and titer is below critical
• If the father is heterozygous or status is unknown, request cell-free fetal DNA (cffDNA) testing at 10-12 weeks
• If the baby is antigen-negative, no further monitoring is needed for that antibody
• If previously affected or with high antibody levels, consider starting IVIG and/or plasmapheresis

Weeks 12–14

• Continue titer monitoring every 4 weeks if the baby is or may be antigen-positive and titer remains below critical

Weeks 15–18

• Begin weekly MCA (Middle Cerebral Artery Peak Systolic Velocities)Doppler scans if any of the following apply:
  • Titer is at or above the critical level
  • You have anti-Kell antibodies
  • You had a previously affected pregnancy, even with a low titer.

Weeks 18–32

• At 26 weeks, increase titer monitoring to every 2 weeks if the baby is or may be antigen-positive and titers remain below critical
• Continue weekly MCA scans if titers reached critical at any point
• If MoM is greater than 1.5 multiples of the median (MoM),, prepare for possible intrauterine transfusion (IUT)
• If IUT is needed:
  • Discuss steroid administration prior to the first procedure
  • Plan to repeat IUTs every (2-3 weeks) as needed
• Monitor fetal growth and wellbeing

Week 32

• Begin antenatal testing, including:
  • Non-stress tests (NSTs), and/or
  • Biophysical profiles (BPPs)

Weeks 34–36

• At 36 weeks, increase titer monitoring to weekly if the baby is or may be antigen-positive and titers remain below critical
• Finalize delivery, hospital and follow-up care plan. Plan to deliver at a hospital that has at least a level 3 NICU and confirm readiness with their care team  including the availability of appropriate unit of blood for possible postnatal transfusion
• Plan timing of delivery, typically between 37–38 weeks regardless of titer status
• Discuss with delivery team delayed clamping of umbilical cord