Expression of hypoxia-induced mRNA in maternal blood from women sampled across labor. (A) Expression of six hypoxia-induced transcripts in paired maternal blood sampled before labor was commenced and moments before delivery. Data were generated using a Taqman PCR array. (B) Hypoxia inducible factor (Hif)1α, HIF2α, adrenomedullin (Adm) and lactate dehydrogenase A (LdhA) expression in serial samples taken before labor was commenced (white bars; n = 30), during the second stage (full cervical dilatation) at either 120 to 180, 61 to 120 or 0 to 60 minutes prior to delivery (gray bars, sampling from the cohort of 30 were split among the three bars), and at the moment of birth (black bar; n = 30). Thus, white and gray bars depict mRNA expression of genes in maternal blood at time-points straddling the beginning and end of the first stage of labor (mean (± SD) 486 (± 242) minutes between sample collection), while the gray and black bars straddle the second stage of labor (mean (± SD) 44 (± 55) minutes between sample collection). Data were generated using Taqman PCR. Mean and S.E.M. are graphed. *P <0.05 **P <0.01 ***P <0.001.