Unlinked anonymous testing to estimate HIV prevalence among pregnant women in Catalonia, Spain, 1994 to 2009

This paper estimates the prevalence of human immunodeficiency virus (HIV) infections in women giving birth and women voluntarily terminating pregnancy over a period of sixteen years in Catalonia. Samples for HIV antibody detection were collected from the Neonatal Early Detection Programme for congenital metabolic diseases that covers 99% of infants born in Catalonia. The sampling method collected information of 50% of births every year and of all women attending three clinics for voluntary interruption of pregnancy. Using two sequential immunoassays we analysed unlinked anonymous blood spot samples from 549,689 newborns between 1994 and 2009 and from 31,904 women who voluntarily interrupted pregnancy between 1999 and 2006. HIV prevalence among women giving birth decreased from 3.2 per 1,000 in 1994 to 1.7 per 1,000 in 2009 (p<0.01) and the mean age of infected mothers increased from 26 years in 1994 to 32 years in 2009 (p=0.001). A decrease in HIV prevalence was also observed in women voluntarily terminating pregnancy, from 2.3 per 1,000 in 1999 to 1.0 per 1,000 in 2006 (p<0.01). In contrast, estimated HIV prevalence in mothers born outside Spain increased from 2.2 per 1,000 in 2002 to 3 per 1,000 in 2009 (p<0.01) and their average age increased from 27 years in 2003 to 31 years in 2009 (p<0.01).