Habitual carbohydrate intake is not correlated with circulating β-hydroxybutyrate levels in pregnant women with overweight and obesity at 28 weeks' gestation

Aims/hypothesis Pregnant women are advised to consume a minimum of 175 g per day of carbohydrate to meet maternal and fetal brain glucose requirements. This recommendation comes from a theoretical calculation of carbohydrate requirements in pregnancy, rather than from clinical data. This study aimed to determine whether fasting maternal ketone levels are associated with habitual carbohydrate intake in a subset of participants of the Study of PRobiotics IN Gestational diabetes (SPRING) randomised controlled trial. Methods Food frequency questionnaires on dietary intake during pregnancy were completed by pregnant women with overweight or obesity at 28 weeks’ gestation (considering their intake from the beginning of pregnancy). Dietary intake from early pregnancy through to 28 weeks was analysed for macronutrient intake. At the same time, overnight fasting serum samples were obtained and analysed for metabolic parameters including serum β-hydroxybutyrate, OGTTs, insulin and C-peptide. Results Fasting serum β-hydroxybutyrate levels amongst 108 women (mean BMI 34.7 ± 6.3 kg/m 2 ) ranged from 22.2 to 296.5 μmol/l. Median fasting β-hydroxybutyrate levels were not different between women with high (median [IQR] 68.4 [49.1–109.2 μmol/l]) and low (65.4 [43.6–138.0 μmol/l]) carbohydrate intake in pregnancy. Fasting β-hydroxybutyrate levels were not correlated with habitual carbohydrate intake (median 155 [126–189] g/day). The only metabolic parameter with which fasting β-hydroxybutyrate levels were correlated was 1 h venous plasma glucose (ρ=0.23, p =0.03) during a 75 g OGTT. Conclusions/interpretation Fasting serum β-hydroxybutyrate levels are not associated with habitual carbohydrate intake at 28 weeks’ gestation in pregnant women with overweight and obesity. Graphical Abstract