30CARE Study Group (2008) Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study. (coffeeandhealth.org)
Research is starting to address these issues by using different types of trials that do a better job simulating «real life», and these pragmatic trials look a lot like prospective observational studies. (birthingnaturally.net)
Tagliabue A, Bertoli S, Trentani C, Borrelli P, Veggiotti P. Effects of the ketogenic diet on nutritional status, resting energy expenditure, and substrate oxidation in patients with medically refractory epilepsy: A 6 - month prospective observational study. (nature.com)