Peripheral venous blood samples were drawn in the morning (NTR 0700–1100, NESDA 0830–0930) after an overnight fast. For fertile women in NTR, samples were obtained on day 3–5 of their menstrual cycle, or in the pill-free week if on oral contraception. Heparinized whole blood was transferred into PAXgene Blood RNA tubes (Qiagen) within 20 minutes (60 minutes for NESDA), incubated, and stored at −20°C or −30°C (NTR). High molecular weight genomic DNA was isolated using Puregene DNA isolation kits (Qiagen).
