Pregnancy protein puzzle: leucine needs under the microscope

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Pregnant women aged 20-40 years. (This age range represents typical reproductive age and minimizes potential confounding effects related to adolescent growth or age-associated metabolic changes.) * Singleton pregnancy. (Restricting participation to singleton pregnancies reduces variability in nutrient requirements and metabolic demands associated with multiple gestations.) * Gestational age of either 11-20 weeks (early gestation) or 31-40 weeks (late gestation). (These time points represent physiologically distinct stages of pregnancy, allowing comparison of leucine requirements across early and late gestation.) * Participants who take part in early gestation, can participate in late gestation, if they meet all inclusion criteria. * Good general health with no acute or chronic medical conditions. (Including only healthy participants minimizes confounding factors that could alter amino acid metabolism and ensures participant safety.) * Fully ambulatory and able to comply with study procedures. (Participants must be able to attend study visits and complete protocol requirements, including dietary intake and sample collection.) * Pre-pregnancy body mass index (BMI) between 19 and 28 kg/m² (This range excludes underweight and obese individuals, whose altered protein and amino acid metabolism could affect study outcomes.) * Carrying a viable pregnancy without known complications at enrollment. (Excluding pregnancy complications at baseline reduces risk to participants and supports accurate assessment of physiological amino acid requirements.) Exclusion Criteria: -Pregnancy-related complications (e.g., hyperemesis gravidarum, GDM, hypertension, pre-eclampsia, anemia). (These conditions may alter metabolism and increase risk, potentially confounding study outcomes.) * History of adverse pregnancy outcomes (spontaneous abortion or preterm birth). (May reflect underlying physiological factors affecting amino acid metabolism.) * Multiple gestation pregnancies. (Nutritional and metabolic demands differ from singleton pregnancies.) * Pregnancy loss within six months of the current pregnancy. (Short intervals may affect maternal nutrient status and metabolic adaptation.) * Chronic metabolic, cardiovascular, neurological, genetic, or immune disorders. (These conditions may independently affect protein and amino acid metabolism.) * Clinically significant claustrophobia. (May interfere with study procedures requiring ventilated hood measurements.) * Use of alcohol, tobacco, or illicit substances during pregnancy. (Substance use affects metabolism and poses maternal and fetal health risks.) * Gestational weight loss greater than 1.5 kg. (May indicate inadequate nutritional status.) * Pre-pregnancy BMI outside 19-28 kg/m². (Extremes of BMI are associated with altered protein metabolism.)