Each year, there are an average of 200 million pregnancies, 300,000 maternal deaths related to pregnancy and birth, and 7 million fetal perinatal deaths worldwide. Maternal biological fluids used to describe the state of a healthy pregnancy and fetal development were important to ensure a successful monitoring. Urine, as a filtrate of the blood, bears no need nor mechanism to be stable, and tolerates changes to a higher degree, which are associated with physiological or pathophysiological processes of the body. Therefore, changes were more easily detected in urine than in blood.

In this study, liquid chromatography-mass spectrometry(LC/MS) was used to monitor the pregnancy process through maternal urinary proteome. Pregnant rats urine samples were collected throughout pregnancy (from GD 0d to GD 21 d), and urine samples were collected from control group at corresponding time points. By comparing with the urinary proteome within groups on the first day of pregnancy, the differential proteins were involved in embryo implantation and trophoblast differentiation. Liver, kidney, and bone development started early to be enriched in the pregnant group, but not in the control group. Interestingly, the developmental processes of the fetal heart such as heart looping and endocardial cushion formation could be seen in urine of pregnant rats. Moreover, the timings were consistent with embryological studies. The timing of fetal lung surfactant appearance in urine was right before birth. The differential proteins related to pancreas development appeared in urine at the time during reported time of pancreatic cell proliferation and differentiation. Furthermore, coagulation-associated pathways were found to be increasingly prominent before labor.

Our results indicated that maternal urinary proteome can reflect the process of pregnancy, even embryonic and fetal development. This study provides a new perspective for early fetal monitoring.