The developmental origins of health and disease (DoHaD) paradigm states the relationship between prenatal exposures and offspring health in later life. So far, this field of research has been mainly focused on the second half of pregnancy and the period just after delivery. From epidemiological and experimental studies, it has become clear that periconception conditions, such as age, ethnicity, chronic diseases, and genetic factors, as well as modifiable lifestyles, such as nutrition, smoking, and alcohol consumption, significantly contribute to human reproductive and obstetric health and performance. The periconception period represents the critical time span of 14 weeks before conception, in which both female and male gametes maturate, followed by the first 10 weeks after conception during which implantation and the early embryonic and placental development take place. Adverse conditions and lifestyle behaviour during these 24 weeks can detrimentally affect these biological processes with consequences for fertility, prenatal growth and development, and the health of the mother and her offspring during the life course. A new focus of reproductive and obstetric medicine should be the preventative care and treatment of the couple before pregnancy: preconception care.
