Diagnosis of HIV infection in pregnancy: data from a national cohort of pregnant women with HIV in Italy.

We analysed the characteristics of the pregnancies with a previously undetected HIV infection in a national observational study of pregnant women with HIV in Italy. In a total of 443 pregnancies with available date of HIV diagnosis, 118 were characterized by a previously undetected HIV infection (26.6%, 95% CI 22.5-30.8). The following factors were independently associated with this occurrence in a multivariate analysis (adjusted odds ratios; 95% CIs): foreign nationality (5.1, 2.8-9.3); no pre-conception counselling (35.9, 4.8-266.1); first pregnancy (2.1, 1.2-4.0); asymptomatic status (6.8, 1.5-30.6). Women with previously undetected infection started antiretroviral treatment significantly later during pregnancy (P < 0.001). Missed diagnosis was responsible for one case of transmission. A high rate of previously undetected HIV infection was observed. This suggests a good HIV detection during pregnancy, but also the need to reinforce HIV testing strategies among women of childbearing age. We identified some determinants which may be considered for intervention measures.