Most women with Turner syndrome have premature ovarian insufficiency from childhood. The chance of a spontaneous pregnancy is higher in women with a Turner mosaicism and in women who have had a spontaneous menarche. This chance is estimated at 5-8%. We discuss 2 women with Turner mosaicism who were misinformed about their chances of a spontaneous pregnancy. In both cases, puberty induction was started because of suspected gonadal dysgenesis but in retrospect only puberty was delayed, while ovarian function was still good at that time. The cases presented show that in long-term follow-up there is a pitfall in adopting incorrect assumptions. Critical re-evaluation of medical data during childhood and adolescence is therefore essential. The impact of infertility is great in women with Turner syndrome. Because pregnancy has an increased risk of complications, an unplanned pregnancy should be prevented.