This document discusses a study conducted in Cyprus that aimed to: 1) assess the feasibility of using cell-free fetal DNA (cffDNA) from maternal plasma to determine fetal RhD status in RhD negative pregnancies, and 2) estimate RhD phenotype and genotype frequencies in the Cypriot population. The study found that fetal RhD status could be accurately determined in 73 pregnancies using cffDNA analysis. Additionally, analysis of 445 random samples found that 7.2% of the Cypriot population is RhD negative, while the frequencies of RHD hemizygosity and homozygosity were estimated to be 39.2% and 53.6%, respectively.
Antenatal prophylaxis with anti-d immunoglobulin Molly Caliger
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This document discusses the role of antenatal immunoprophylaxis in preventing maternal-fetal anti-Rh(D) alloimmunization. It provides a brief history of the discovery of Rh disease and the development of anti-D immunoglobulin G treatment. The rationale for antenatal prophylaxis is to prevent sensitization from occult transplacental hemorrhages during pregnancy. Studies show antenatal prophylaxis starting at 28 weeks and dosing of 25 micrograms of anti-D IgG is effective at reducing immunization rates below 1%.
This document summarizes the challenges of communicating risk in prenatal screening tests. It discusses how:
1) Prenatal screening tests have a high rate of false positives, leading many women with healthy pregnancies to undergo invasive follow-up tests that carry risks of miscarriage. For example, a first trimester screening test with a 5% false positive rate could lead to around 50 unnecessary miscarriages among 100,000 screened women.
2) Calculating and understanding the positive predictive value of screening tests, which is needed for informed decision making, requires Bayesian reasoning that most people struggle with. As a result, risks are often underestimated.
3) While research has identified effective ways to communicate Bayesian concepts