Sample collection

Decidual tissue was isolated from foetal membrane samples collected from women who delivered at Edinburgh Royal Infirmary, with written and informed consent, according to the ethical approval and governance granted to the Edinburgh Reproductive Tissues BioBank by the West of Scotland Research Ethics Committee 4 (REC reference: 09/S0704/3) until 30/09/2014; and consequently by the East of Scotland Research Ethics Service Tayside Committee on Medical Research Ethics B (REC reference: 13/ES/0126).

Samples were collected from women delivering at term (38–42 weeks of gestation) and preterm (<35 weeks of gestation). A total of 36 women were recruited from four patient groups: term not in labour (TNL; n = 11), term in labour (TL; n = 8), preterm not in labour (PTNL; n = 7) and preterm in labour (n = 10). TNL and PTNL samples were collected from women following caesarean section delivery; TL and PTL samples were collected following either vaginal delivery or emergency caesarean section delivery. Patient characteristics are detailed in Table ​TableII.

Demographic and clinical characteristics of the study groups^a.

^aThe numbers are median and range unless otherwise indicated.

^bParity data were missing from one patient in the PTL group.

^cBMI at booking to antenatal care. Due to patient transfer, BMI was not available for three PTNL patients and three PTL patients.

^dChorioamnionitis status from available pathology reports for preterm patients. Pathology reports were not available for two PTL patients.

^ePlacental abruption confirmed from available pathology reports from preterm patients. Pathology reports were not available for two PTL patients.

*P < 0.05, **P < 0.01 versus TNL; ^##P < 0.01, ^####P < 0.0001 versus TL; Kruskal–Wallis with post hoc Dunn test.

Following delivery, full-thickness foetal membranes were cut from the placenta and placed in PBS. Samples were either stored at 4°C for no more than 1–5 h before processing, or processed immediately following collection. Amnion was removed from the foetal membranes and decidua parietalis tissue was carefully scraped from the chorion. Samples of decidual tissue were either frozen at −80°C for further RNA and protein analysis or digested for isolation of decidual lymphocytes.