Postpartum Metabolism: How Does It Change from Pregnancy and What are the Potential Implications?

BACKGROUND: Metabolic dysfunction after pregnancy may have serious consequences for a new mother. The purpose of the study was to characterize basic changes that occur in metabolic profiles from late pregnancy through 4–6 months postpartum. A secondary purpose was to determine metabolic factors that may be contributing to postpartum weight retention. METHODS: Participants (n=25) came in for 2 visits: late pregnancy (~34 weeks gestation) and postpartum (4-6 months). Resting metabolic rate (RMR), respiratory quotient (RQ), and substrate oxidation values were assessed for 15 minutes during fasted conditions. Blood was drawn and skinfold anthropometry was performed to assess additional outcomes (inflammation, insulin resistance, lipid profiles, body composition). The participants completed a number of surveys that examined other lifestyle and demographic data of interest. At the postpartum visit, additional assessments regarding sleep and breastfeeding habits were administered. RESULTS: RMR was lower during postpartum (1517.2±225.1 kcal/day) compared to pregnancy (1867.9±302.6 kcal/day) (p<0.001), and remained lower when expressing RMR per kg body weight (postpartum: 22.3±2.7 vs pregnant: 23.7±3.4 kcal/kg, (p=0.034). Relative RMR (RMR per kg body weight) was negatively correlated to insulin resistance (HOMA-IR) during postpartum (r=−.463, p=0.034). Maternal HOMA-IR, inflammation (CRP), triglycerides (TAG), and carbohydrate oxidation were all positively correlated to postpartum weight retention (HOMA-IR: r=0.617, p=0.004; CRP: r=0.477, p=0.039, TAG: r=0.463, p=0.040; Carbohydrate Oxidation: (r=0.469, p=0.018). CONCLUSION: Metabolic rate is lower during postpartum compared to pregnancy, and may be connected to insulin resistance. Maternal insulin resistance, inflammation, blood lipids, and substrate metabolism are all related to postpartum weight retention.