To test the hypthesis that preterm spontaneous labor involves aberrant 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 preterm spontaneous delivery (<34 weeks) and term spontaneous delivery (38–39 weeks) by gene expression microarray. Indicated preterm births, threatened preterm labor (term birth), multiple pregnancies, pregnancies complicated by preeclampsia, intrauterine growth restriction, fetal chromosomal and structural abnormalities were excluded from the study. 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 spontaneous preterm birth 5
Control placenta normal pregnancy 5
Gene Fold Change (log2) Significance Genus Species