Are elevated FSH concentrations in the pre-conceptional period a risk factor for Down's syndrome pregnancies?

Recent publications have reported a relation between a decreased ovarian re serve and Down's syndrome pregnancies. Using the data of a case-control stu dy into risk factors for a Down's syndrome pregnancy, we estimated the usef ulness of pre-conceptional basal follicle stimulating hormone (FSH) screeni ng (detection rate, false positive rate, positive and negative likelihood r atio, as well as the loss rate of unaffected pregnancies) to identify Down' s syndrome pregnancies. The optimal detection rate of pre-conceptional basa l FSH screening for Down's syndrome pregnancies was 14%, corresponding to a false positive rate of 5% and a positive likelihood ratio of 2.8, Incorpor ation of basal FSH screening into the regimen of first trimester serum scre ening followed by nuchal translucency measurement would increase the detect ion rate from 85 to 87%, However, basal FSH screening alone or in combinati on with other screening methods would cause an unacceptably high loss rate of unaffected pregnancies compared with current screening protocols, indica ting that routine pre-conception basal FSH screening would not be useful to identify women at risk for a Down's syndrome pregnancy. However, when elev ated basal FSH concentrations are diagnosed during subfertility evaluation, an elevated risk for a Down's syndrome pregnancy could be discussed with w omen who become pregnant.