Numbers of PND requests for hemoglobinopathies during 2009–2021, grouped according to necessary (n = 3,880) and unnecessary (n = 645) requests and requests with inadequate data for fetal risk assessment (n = 409).

Numbers of requests with known and unknown parental mutations prior to fetal sampling and the risks for hemoglobinopathies of the fetuses are listed. CS = Hemoglobin Constant Spring, thal = thalassemia.