[Normal implantation is important in order to avoid pregnancy complications and diseases later in life]

Normal placentation is important to avoid complications in pregnancy and diseases later in life. Infertility, spontaneous abortions, intrauterine growth retardation and preeclampsia may be a spectrum of disorders all caused by poor placentation. The aetiology may in all instances be due to decreased interaction between the trophoblasts and the endometrium/decidua, although in different degrees. Implantation is to a large extent controlled by a complex interplay between surface molecules on trophoblasts and cells in the uterus. Different cytokines, enzymes, receptors and adhesion molecules play an essential role. Defect placentation may lead to "programming", whereby an insult suffered at a critical period of development results in a permanent effect on the structure or function of the organ or tissue. Poor growth in utero is associated with diseases like hypertension and diabetes later in life. Over-invasion of trophoblasts may result in placenta accreta/pancreata and uterine rupture. Under-invasion may lead to preecklampsia, growth retardation and spontaneous abortion. Therefore, the balance between trophoblast invasion and maternal defence must be maintained in order to obtain successful pregnancy outcomes. Unravelling how this is done remains a major challenge in reproductive biology.