The investigators hypothesize that cardio-metabolic and hemodynamic abnormalities reducing cardiovascular reserves relate to circulatory redistribution at the expense of uterine perfusion and with it women's fertility. This could especially be important in the subgroups with an unexplained subfertility and a decreased ovarian reserve. Interventions to improve these abnormalities could lead to better results in fertility treatment, better obstetric outcome and reduced lifelong health risks.