First trimester aneuploidy screening is routinely used in pregnancy follow-ups. In this screening, free /l-hCG and pregnancy-associated plasma protein A (PAPP-A) levels in the blood of the pregnant woman arc measured. The aim of this study is to investigate the relationship between PAPP-A levels, maternal characteristics, diabetes, ultrasound measurements of the fetus and other biochemical markers of the aneuploidy screening. In this study, we used the dataset of 12 428 pregnant women, who arc followed by some of our researchers at the Prenatal Unit of Yale University Hospital in USA. The correlation of free-13-hCG, PAPP-A and Down syndrome risk with thyroid stimulating hormone (TSH), glucose and hematocrit was analyzed. A statistically significant correlation (p=0.0005) was found between the PAPP-A levels in the group of diabetic pregnant% and PAPP-A levels in non diabetic pregnant group. Detailed studies on the effect of PAPP-A on insulin growth factor could make it possible to use PAPP-A levels to predict gestational diabetes.