Maternal blood specimen collection and processing
FRANKLIN
Upon human milk specimen pick-up, participants opted to provide a non-fasting blood specimen for plasma UMFA and 5-MTHF analysis, collected in a 6-mL EDTA tube (BD Biosciences, Franklin Lakes, NJ). To match conditions at the human milk collection, participants were instructed to consume their folate supplements 2 h prior to the blood draw. Vacutainers were shielded from light, inverted gently, and transported to the laboratory for immediate processing (within 2 h of collection). Vacutainers were centrifuged at 3000 rpm × 15 min at 4 °C. Plasma was aliquoted and stored at -80 °C.