During pregnancy, the future mother can develop several different diseases. Most of them have a benign prognosis. Cyanotic heart disease, at least when it is accompanied by significant pulmonary hypertension or induces a functional class IV represents a contra-indication to pregnancy. Pregnancy cardiomyopathy generally carries a poor prognosis and may be responsible for the mother's death. Herpes virus pneumopathy can also be extremely dangerous. Lupus erythematosus represents a factor of guarded prognosis for the outcome of pregnancy; discontinuation of the latter should be seriously considered. Hepatic steatosis which is a rare diagnosis must be distinguished from Hellp syndrome in which the maternal prognosis is much better. In this review, we shall briefly discuss various medical diseases which may have a deleterious influence on the evolution of pregnancy or on the foetus. These deleterious influences can be direct, i.e. due to the disease, or indirect, i.e. due to the therapy. We shall successively consider several neurological, cardiological, pulmonary, dermatological and digestive diseases. We shall not take into account viral infections or infections in general, diabetes mellitus or the various vasculo-renal syndromes.