This observational study was conducted over 18 months in Departments of Pediatrics, and Obstetrics and Gynecology, Umaid Hospital, Dr. Sampurnanand Medical College, Jodhpur, India. Pregnant women in first trimester and early second trimester (<16 weeks), who were willing for carrier screening, were screened by hematological indices after an informed consent. Detailed history to ascertain the ethnic descent, and any history of blood transfusion was obtained. Complete blood count was done on automated cell counter (Sysmex K-100) and hematological parameters were recorded for 1500 women. HbA2 estimation was done in females with either of the following: (a) MCV <77 fL (b) MCH <27 pg, (c) Mentzer Index <13, (d) family history of thalassemia, (e) high risk ethnic groups – Punjabis, Sindhis, Gujaratis, Bohris and Malis, (f) history of blood transfusion, or (g) unexplained chronic anemia. Women who attended the antenatal clinics in late second trimester and third trimester or those who did not consent were excluded. HbA2 estimation was performed using HPLC (High Performance Liquid Chromatography). HbA2 >3.5% confirmed the diagnosis of b-thalassemia trait. Those with HbA2 in the borderline range (3.3-3.4%) were screened for thalassemia mutations by ARMS-PCR (Amplification Refractory Mutation System - Polymerase Chain Reaction). Chorionic villous sampling (CVS) was done if gestational age was <12 weeks and amniocentesis was preferred for cases detected in later weeks of pregnancy. ARMS-PCR was used for genetic analysis.

Out of 1500 pregnant women, 450 required HbA2 estimation, and 88 (5.9%) were diagnosed as b-thalassemia trait. Mean (SD) age and gestational age of these women was 25.2 (4.2) y and 11.8 (1.4) wk, respectively. Forty-five (45%) had family history of thalassemia. Husbands of 80 of these women responded for screening and 20 proved to be thalassemia trait. Seventeen out of 20 at-risk couples agreed for prenatal diagnosis. Amniocentesis was done in thirteen and CVS in four pregnancies. Two fetuses were detected as having thalassemia major, and medical termination of pregnancy was done. Eleven fetuses were detected as having thalassemia trait and 4 without any b-globin chain abnormality. The mutations detected are depicted in Table I. Most common mutations were IVS 1-5 (G-C) > Fs8/9 b-globin>619bpdel=fs41/42=codon 30G-C>codon b8>Cap+1 (A-C). Five most common mutations were present in 77% of alleles. No complication occurred in CVS/amniocentesis conducted.

TABLE I Results of Mutation Analysis in the Study Children (N=17)

The sample size of our study was small and three couples could not be persuaded for prenatal diagnosis despite repeated counseling. Colah, et al. [1] conducted prenatal diagnosis on only 15 out of 37 at-risk couples over a period of 7 years, and Xu, et al. [2] carried prenatal diagnosis in 11 out of 12 at-risk couples. Five common mutations were reported to be present in 89% thalassemia patients in an earlier study [3] from India. Saxena, et al. [3] reported abortion rate of 3.9% following prenatal diagnosis. Antenatal screening of pregnant females is the most feasible and effective method to reduce birth of children with thalassemia. Carrier screening for thalassemia and hemoglobinopathies should be offered and genetic counseling should be done to women at-risk of these disorders.

1. Colah R, Surve R, Wadia M. Carrier screening for b-thalassemia during pregnancy in India: a 7-year evaluation. Genet Test. 2008;12:181-6.　

2. Xu X, Liao C, Liu Z, Huang Y, Zhang J, Li J, et al. Antenatal screening and fetal diagnosis of b-thalassemia in a Chinese population: prevalence of the b-thalassemia trait in the Guangzhou area of China. Hum Genet. 1996;98: 199-202.

3. Saxena R, Jain PK, Thomas E, Verma IC. Prenatal diagnosis of b-thalassemia: Experience in a developing country. Prenat Diagn. 1998;18:1-7.