In countries where the protocols for Hemoglobinopathy prevention have been successfully implemented the role of obstetrician gynecologists and midwifes have been fundamental. Prevention strategies have shown a high degree of compliance and are ethically and socially accepted. Primary prevention begins with basic information and carrier diagnostics either at the pre-conception stage (usually started by the general practitioner) or in early pregnancy (by routine analysis of the mother at 10 weeks of gestation or earlier).
A simple routine analysis is sufficient to exclude the carrier status for HbS, HbE, HbC, HbD, β- and eventually α- thalassemia in the mother and to rule out the risk for major Hemoglobinopathy in the child. If the mother results to be carrier a rapid analysis of the father in an experienced laboratory is necessary. If only the mother is a carrier no risk for major Hemoglobinopathy is present. If both parents are carrier, prenatal diagnosis can be offered to the couple at risk by chorion villi analysis from the 11th week of pregnancy.
Netherlands, Great Britain, Italia, Greece, Cyprus
The “World Health Organization” has established that 5% of the world population is a carrier of HbP.
Carriers of the most common HbP’s (HbS, HbE, HbC, HbD, α- and β-thalassemia) are highly frequent especially in Mediterranean, African and Asiatic populations. This is as a consequence of a selection mechanism which protects HbP carriers from the severe consequences of malaria tropica infection.
The price for this genetic advantage is the risk that parents who are both carriers run of having progeny severely affected with one of the major HbP forms (Thalassemia major and sickle cell disease).
Couples at risk have 25% chance of a severe HbP in their progeny. Thus 350,000 affected children are born worldwide each year.
HbS, HbC, HbE and HbD are frequent in the Dutch population of recent foreign origin as well as in the population of other Northern European countries with an elevated foreign population. All these mutants are β-globin defects and are recessively inherited (Thus no severe symptoms in the carriers). Conversely, children of parents who are both carriers may be homozygous or double heterozygous for combinations such as HbS/S, S/D, S/E, S/β-thal, HbE/β-thal and be affected shortly after birth by a very severe pathology.
β- and α-thalassemia are also frequent in the immigrant populations of Northern European countries. Also these disease are mostly recessively inherited. The pathology in patients with β-thal major (β-thal/β-thal, HbS/β-thal, HbE/β-thal, etc..) manifests at about 6 months of age and is usually very severe. The α-thalassemias present as severe forms during prenatal life (Hb Bart’s hydrops foetalis) only if the expression of the 4 available α-genes is totally absent.
The postnatal pathology of α-thalassemia is mild with 1 or 2 and intermediate with 3 affected genes (HbH disease). It would be worthwhile to pay attention to prevention of these severe inherited blood diseases called hemoglobinopathies. The role of the midwife and the gynecologist is fundamental in recognizing potential carriers, provide carriers with information and refer couples at risk to the clinical geneticist for counseling. The health professional should realize that this trait is familial, and think of cascade screening. Young carrier couples are entitled to know about the genetic risk of having an affected child with Sickle Cell Disease of Thalassemia Major, and should be offered counseling to make an informed choice.