LONGITUDINAL FOLLOW-UP-STUDIES

A longitudinal study should be undertaken only when there is a clear r eason to justify this and a reasonable chance of achieving the objecti ves. A multidisciplinary approach is often required, and continuity of staff and long-term collaboration with colleagues are important for t heir success. A longitudinal approach is required to estimate the prev alence of an infection in pregnancy and the rate of vertical transmiss ion and to clarify the natural history in infected children. An exampl e of cytomegalovirus infection is given; the parallels with HIV are ob vious.