Relative risk of early preterm birth as related to total omega-3 fatty acids in whole blood (Simmonds et al., 2020). We were able to calculate cut-points for omega-3 fatty acids that were indicative of risk for depletion and sufficiency. In women with a total omega-3 status ≤ 4.1% of total fatty acids, omega-3 supplementation substantially reduced the risk of early preterm birth compared with control. Conversely, supplementing women with a baseline status above 4.9% increased early preterm birth. This highlights the need for accurate assessment on omega-3 status early in pregnancy.