To test the hypothesis that the labor process involves changes in mRNA expression in the placenta, Chim et al. interrogated the mRNA levels of >50,000 genes and transcript variants in placentas collected from term spontaneous delivery and elective term cesarean delivery by gene expression microarray. To minimize the effect of gestational age on gene expression, the two groups were matched for gestational age at delivery. A piece of placental tissue (about 0.1 cm³) was biopsied immediately after delivery. Care was taken to minimize the contamination of any maternal decidual tissue, fetal membranes, and blood clots in the biopsied placental tissue.

Tissue Condition Samples
Test placenta elective term cesarean section 4
Control placenta normal pregnancy 5
Gene Fold Change (log2) Significance Genus Species