Maternal prepregnancy BMI and GWG, including period-specific GWG, were positively and independently associated with neonatal adiposity. Associations of early and midpregnancy weight gain with neonatal adiposity support the hypothesis that greater maternal weight gain during pregnancy, regardless of prepregnancy BMI, is directly related to offspring adiposity at birth. The Healthy Start study was registered as an observational study at clinicaltrials.gov as NCT02273297.

Many researchers favor repeated measures designs because they allow the detection of within-person change over time and typically have higher statistical power than cross-sectional designs. However, the plethora of inputs needed for repeated measures designs can make sample size selection, a critical step in designing a successful study, difficult. Using a dental pain study as a driving example, we provide guidance for selecting an appropriate sample size for testing a time by treatment interaction for studies with repeated measures. We describe how to (1) gather the required inputs for the sample size calculation, (2) choose appropriate software to perform the calculation, and (3) address practical considerations such as missing data, multiple aims, and continuous covariates.

GLIMMPSE is a free, web-based software tool that calculates power and sample size for the general linear multivariate model with Gaussian errors (http://glimmpse.SampleSizeShop.org/). GLIMMPSE provides a user-friendly interface for the computation of power and sample size. We consider models with fixed predictors, and models with fixed predictors and a single Gaussian covariate. Validation experiments demonstrate that GLIMMPSE matches the accuracy of previously published results, and performs well against simulations. We provide several online tutorials based on research in head and neck cancer. The tutorials demonstrate the use of GLIMMPSE to calculate power and sample size.

Background and Objective Poor maternal diet in pregnancy can influence fetal growth and development. We tested the hypothesis that poor maternal diet quality during pregnancy would increase neonatal adiposity (percent fat mass, %FM) at birth by increasing the fat mass (FM) component of neonatal body composition. Methods Our analysis was conducted using a pre-birth observational cohort of 1,079 mother-offspring pairs. Pregnancy diet was assessed via repeated Automated Self-Administered 24-hour dietary recalls, from which Healthy Eating Index-2010 (HEI-2010) scores were calculated for each mother. HEI-2010 was dichotomized into scores ≤ 57 and scores > 57, with low scores representing poorer diet quality. Neonatal %FM was assessed within 72 hours after birth with air displacement plethysmography. Using univariate and multivariate linear models, we analyzed the relationship between maternal diet quality and neonatal %FM, FM, and fat-free mass (FFM) while adjusting for pre-pregnancy body mass index (BMI), physical activity, maternal age, smoking, energy intake, preeclampsia, hypertension, infant sex, and gestational age. Results Total HEI-2010 score ranged between 18.2 and 89.5 (mean: 54.2, SD: 13.6). An HEI-2010 score ≤ 57 was significantly associated with higher neonatal %FM (β = 0.58, 95% CI 0.07, 1.1, p<0.05) and FM (β=20.74; 95% CI 1.49, 40.0; p<0.05) but no difference in FFM. Conclusions Poor diet quality during pregnancy increases neonatal adiposity independent of maternal pre-pregnancy BMI and total caloric intake. This further implicates maternal diet as a potentially important exposure for fetal adiposity.

Objective To examine associations between pregnancy physical activity and neonatal fat mass and fat-free mass, birth weight and small for gestational age (SGA). Methods We analyzed 826 mother-neonate pairs (term births) participating in the longitudinal Healthy Start study. The Pregnancy Physical Activity Questionnaire was used to assess total energy expenditure and meeting American College of Obstetricians and Gynecologists (the College) guidelines for physical activity during early pregnancy, mid-pregnancy and late pregnancy. Models were adjusted for maternal and neonatal characteristics. Results Neonates had mean fat mass of 292.9 grams, fat-free mass of 2,849.8 g, and birth weight of 3,290.7 g. We observed 107 (12.9%) SGA and 30 (3.6%) large-for-gestational age (LGA) births. A significant inverse linear trend between total energy expenditure during late pregnancy and neonatal fat mass (Ptrend = 0.04) was detected. Neonates of mothers in the highest compared to lowest quartile of total energy expenditure during late pregnancy had 41.1 g less fat mass (249.4 vs. 290.5 g; P = 0.03). No significant trend was found with total energy expenditure and neonatal fat-free mass or birth weight. Early-pregnancy and mid-pregnancy total energy expenditure were not associated with neonatal outcomes. No significant trend was observed between late-pregnancy total energy expenditure and SGA (Ptrend = 0.07), but neonates of mothers in the highest compared to the lowest quartile had a 3.0 (95% CI 1.4–6.7) higher likelihood of SGA. Meeting the College’s physical activity guidelines during pregnancy was not associated with differences in neonatal outcomes. Conclusions Increasing levels of late-pregnancy total energy expenditure are associated with decreased neonatal adiposity without significantly reduced neonatal fat-free mass.

Maternal insulin resistance in the first half of pregnancy is highly predictive of neonatal FM%, whereas maternal glycemia, even within the normal range, is an important driver of neonatal adiposity in later pregnancy, independent of prepregnancy BMI. Our data provide additional insights on potential maternal factors responsible for fetal fat accretion and early development of adiposity.

Background Consistent evidence of an influence of maternal dietary intake during pregnancy on infant body size and composition in human populations is lacking, despite robust evidence in animal models. Objective To evaluate the influence of maternal macronutrient intake and balance during pregnancy on neonatal body size and composition, including fat mass and fat free mass. Study Design The analysis was conducted among 1040 mother-offspring pairs enrolled in the prospective pre-birth observational cohort: The Healthy Start Study. Diet during pregnancy was collected using repeated 24 hour dietary recalls (up to 8). Direct measures of body composition were obtained using air displacement plethysmography. The National Cancer Institute measurement error model was used to estimate usual dietary intake during pregnancy. Multivariable partition (non-isocaloric) and nutrient density (isocaloric) linear regression models were used to test the associations between maternal dietary intake and neonatal body composition. Results The median macronutrient composition during pregnancy was 32.2% from fat, 15.0% from protein and 47.8% from carbohydrates. In the partition multivariate regression model, individual macronutrient intake values were not associated with birth weight or fat free mass, but were associated with fat mass. Respectively, 100 kilocalorie increases in total fat, saturated fat, unsaturated fat and total carbohydrates were associated with 4.2 gram (p=0.03), 11.1 gram (p=0.003), 5.9 gram (p=0.04) and 2.9 gram (p=0.02) increases in neonatal fat mass, independent of pre-pregnancy BMI. In the nutrient density multivariate regression model, macronutrient balance was not associated with fat mass, fat free mass or birth weight after adjustment for pre-pregnancy BMI. Conclusions Neonatal adiposity, but not birth weight, is independently associated with increased maternal intake of total fat, saturated fat, unsaturated fat, and total carbohydrates, but not protein, suggesting that most forms of increased caloric intake contribute to fetal fat accretion.

Aims/hypothesis In women who are overweight or obese before or during pregnancy there is an associated risk of increased fetal growth and higher birthweight. The metabolic phenotype of the overweight/obese pregnant woman, characterised by higher than normal insulin resistance (IR) and increased circulating fuels, suggests a mechanism resulting in fetal overnutrition and subsequent increased adiposity. We tested the fuel-mediated hypothesis in an observational pre-birth cohort of 951 mother–offspring pairs, the Healthy Start study. Methods We conducted a path analysis to estimate the simultaneous effects of maternal IR and maternal fuels (fasting glucose, triacylglycerol [TG] and NEFA levels) in late pregnancy in mediating the relationship between maternal pre-pregnancy BMI and neonatal adiposity (per cent fat mass [%FM]). Results The total effect of maternal BMI on neonatal %FM was significant (total effect 0.16, 95% CI 0.08, 0.22, p < 0.001). The mediated path including maternal IR and glucose levels together accounted for 21% (p < 0.01) of the total effect of maternal BMI on neonatal %FM while the mediating effects of all other fuels were non-significant. Conclusions/interpretation Using a novel application of path analysis our data implicate maternal IR and glucose levels as important mediators of the association between maternal and infant adiposity.