The present invention is focused on an in vitro method for identifying or screening human subjects at risk of suffering from a pregnancy related disease, in particular from gestational diabetes mellitus or preeclampsia, departing from the level of expression or concentration of a series of biomarkers isolated from a minimally-invasive sample such as gingival crevicular fluid (GCF). Moreover, the method of the invention offers high sensitivity and specificity at an early stage of the pregnancy (see the Examples and figures shown below), which means that it is a strong and cost-effective method for the detection of a pregnancy related disease, in particular gestational diabetes mellitus or preeclampsia, at an early stage of the disease thus procuring effective treatment, avoiding significant long-term adverse effects for both mother and baby.