Safe fetal platelet genotyping: new developments.

Area of Science:

• Genetics
• Immunology
• Obstetrics

Background:

• Fetal and neonatal alloimmune thrombocytopenia (FNAIT) arises from maternal antibodies against fetal platelet (PLT) antigens.
• Intracranial hemorrhage is a significant complication of FNAIT, necessitating antenatal management.
• Human Platelet Antigen (HPA)-1 is the most common cause of FNAIT in Caucasian populations.

Purpose of the Study:

• To develop two reliable, noninvasive fetal genotyping assays.
• To determine fetal risk in pregnancies where the father is heterozygous for the HPA-1 antigen.
• To enable early antenatal management of FNAIT.

Main Methods:

• Development of two real-time polymerase chain reaction (QPCR) assays using cell-free fetal DNA from maternal blood.
• An allele-specific QPCR targeting the HPA-1 polymorphic sequence.
• High-resolution melting curve analysis of amplicons containing the HPA-1 polymorphic region.

Main Results:

• Assays were validated on 49 samples from 29 pregnant women.
• Results were consistent with expected fetal antigen compatibility.
• Identified incompatibility in 41 HPA-1bb and two HPA-1aa mothers with their fetuses, and compatibility in six mothers.

Conclusions:

• Two fetal PLT genotyping assays using maternal blood are reliable.
• These noninvasive assays are effective from 15 weeks of gestation.
• The developed assays avoid the need for invasive procedures like amniocentesis.