Clinical immunology, already a subspecialty within internal medicine, is achieving increasing importance within the field of reproductive medicine. The recent recognition that subclinical autoimmune processes may be causally related to repeated early-pregnancy loss has allowed for the conceptional connection between the fields of infertility and obstetrics. While the immunology of infertility has been in mainstream clinical practice for years, clinical application of immunologic knowledge in obstretrics has somewhat lagged behind. The review presented here is an attempt to summarize recently recognized immune processes which affect pregnancy. Pregnancy seems particularly susceptible to immunologic interference during the very early and very late stages of gestation. During early pregnancy subclinical autoimmune processes seem capable of causing both pregnancy loss as well as congenital fetal abnormalities such as congenital heart block. Very acutely occurring immune processes in late pregnancy can endanger both maternal and fetal life and need therefore to be clinically recognized as such. The considerable progress in the clinical immunology of pregnancy made over the last few years needs to be continued by defining the clinically observed processes immunologically and biochemically in more detail. The thus obtained knowledge will not only benefit the clinical management of immunologically affected pregnancy, but will also enhance the general understanding of many far wider-reaching immunological processes. After all, pregnancy represents an unique model of nature.