In view of the sparse available data concerning the main infectious illnesses screened for during pregnancy (toxoplasmosis, rubella, syphilis, hepatitis B virus and HIV) in the Northern Province and generally throughout New Caledonia, we decided to undertake a retrospective study based on the files of pregnant women having consulted between September 1996 and September 1999 in the East-Coast provincial hospital (New-Caledonia). First, we wished to estimate the prevalence of toxoplasmosis, rubella, syphilis, hepatitis B virus and HIV Second, we wished to specify the main characteristics of these pregnant women, to trace the evolution of seroprevalence over the study time period and consider the influence of various factors such as age, place of residence and professional occupation. The biological study of these pregnancies was hindered by the fact that approximately half of women consult only from the second trimester of their pregnancy. This result underlines the importance of emphasising efforts aiming to bring women to consult earlier and of improving the regularity and also the interpretation of serological tests (especially for toxoplasmosis serology). Within this population, we found the following percentages of seroprevalence: for toxoplasmosis between 83.6% and 89.6% (zone of hyperendemla), for rubella between 91.6% and 95.8%, for syphilis between 7% and 12.4%, for hepatitis B virus between 61.8% and 76% (for women immune to hepatitis B, the frequency of acquisition of immunity by viral infection was understood between 64.3% and 80.3%) and for HIV 0%. The hepatitis B surface antigen (HbsAg) carrier rate was estimated between 1.7% and 4.9%. Following and informing pregnant women of the risk of toxoplasmosis appears to be of key importance as well as screening HbsAg carriers in order to limit viral transmission to the foetus.