Background: The Tanzania National AIDS Control Programme has established HIV sentinel surveillance among antenatal clinic (ANC) attendees as one of the methods for collecting data on HIV prevalence. This article provides trends on HIV prevalence for 92 sentinel sites that have constantly been part of the surveillance system since 2001 and have participated in at least three consecutive rounds.

Method: The surveillance population included all pregnant women aged 15–49 years who were attending a selected sentinel ANC site for the first time for any pregnancy between 2001 and 2011. Serial testing for HIV infection was done anonymously by detecting for the presence of IgG antibodies to HIV on dried blood spot (DBS) specimens. HIV trends were calculated taking into account random effects from sites on the following variables: region, sites and socio-demographic characteristics defined as age, marital status, parity, education level and duration of stay at present residence.

Results: Overall, there was a significant decline in HIV prevalence from 9.6% in 2001 to 5.6% in 2011 (p<0.01). Specifically, the HIV prevalence among 15-24 years’ pregnant women significantly declined from 7.8% in 2001/2002 to 4% in 2011 (p<0.01). The decline in HIV prevalence occurred irrespective of residence, marital status, education level or previous pregnancies.

Conclusion: There has been a significant decline in HIV infections among young pregnant women attending ANC clinics in Tanzania since 2001. This study also indicates that ANC surveillance among pregnant women over time can provide useful estimates of HIV situation between the population surveys.