Impact of gestational weight gain on fetal growth in obese normoglycemic mothers: a comparative study

Fetal growth trajectories and their association with maternal and child characteristics

Background: The growth of the fetus is a complex process, influenced by genetic and environmental factors. Longitudinal patterns of fetal growth are required to fully understand this process, however to date, a paucity of data exists in this area.Objective: To identify fetal growth trajectories in-utero and to assess their association with maternal and child characteristics up to 5 years postnatal.Methods: Data from 781 mother-child pairs from the ROLO longitudinal birth cohort study were analyzed. The ROLO study was a randomized control trial of a low glycemic index diet in pregnancy to prevent recurrence of macrosomia. Fetal ultrasound measurements were recorded at 20 and 34 weeks gestation, and birth weight was recorded. Abdominal circumference (AC), weight (fetal weight, or birth weight), a standardized proxy for length (femur length or birth length, individually standardized), and AC:length ratio were examined for trajectory classes using latent class trajectory mixture models. Two-, three-, four-, and five-class models were evaluated for fit, using a linear (first order) trajectory over three time-points. ANOVA and chi-square tests were applied to test associations between trajectory membership and maternal and child characteristics up to age 5.Results: For AC, two fetal growth trajectories were identified, with 29% of participants on a "slow" trajectory and 71% on a "fast" trajectory. Those on a fast trajectory had higher rates of maternal impaired glucose tolerance (28.7 versus 16.5%, p<.001) and higher rates of mean child 5-year body mass index (BMI) centiles (64th versus 58th centile, p<.05) compared to those on the slow trajectory. For estimated fetal weight, four trajectories were identified, with 4% on a "very-slow" trajectory, 63% in a "moderate-slow" trajectory, 30% in a "moderate-fast" trajectory and 3% on a "very-fast" trajectory. Mothers with a fetus on the fastest trajectory had higher antenatal serum glucose levels (p<.05), and were more likely to deliver by cesarean section (59.1 versus 20%, p<.001). At 5 years of age, children on the fastest growth trajectory had the highest mean BMI centile (86th versus 60th centile, p<.05).Conclusions: This study shows that specific fetal growth trajectories may be associated with maternal serum glucose concentrations during pregnancy, mode of delivery and child BMI at 5 years of age. Diet and lifestyle measures that target maternal glucose levels during pregnancy may have lifelong benefits for children's BMI. Identifying those on an accelerated growth trajectory during fetal life provides a unique opportunity for antenatal and infant interventions that may have long-lasting health benefits.

Association between Birth Characteristics and Cardiovascular Autonomic Function at Mid-Life

Background

Low birth weight is associated with an increased risk of cardiovascular diseases in adulthood. As abnormal cardiac autonomic function is a common feature in cardiovascular diseases, we tested the hypothesis that low birth weight may also be associated with poorer cardiac autonomic function in middle-aged subjects.

Methods

At the age of 46, the subjects of the Northern Finland Birth Cohort 1966 were invited to examinations including questionnaires about health status and life style and measurement of vagally-mediated heart rate variability (rMSSD) from R-R intervals (RRi) and spontaneous baroreflex sensitivity (BRS) in both seated and standing positions. Maternal parameters had been collected in 1965–1966 since the 16^th gestational week and birth variables immediately after delivery. For rMSSD, 1,799 men and 2,279 women without cardiorespiratory diseases and diabetes were included and 902 men and 1,020 women for BRS. The analyses were adjusted for maternal (age, anthropometry, socioeconomics, parity, gestational smoking) and adult variables (life style, anthropometry, blood pressure, glycemic and lipid status) potentially confounding the relationship between birth weight and autonomic function.

Results

In men, birth weight correlated negatively with seated (r = -0.058, p = 0.014) and standing rMSSD (r = -0.090, p<0.001), as well as with standing BRS (r = -0.092, p = 0.006). These observations were verified using relevant birth weight categories (<2,500 g; 2,500–3,999 g; ≥4,000 g). In women, birth weight was positively correlated with seated BRS (r = 0.081, p = 0.010), but none of the other measures of cardiovascular autonomic function. These correlations remained significant after adjustment for potential confounders (p<0.05 for all).

Conclusions

In men, higher birth weight was independently associated with poorer cardiac autonomic function at mid-life. Same association was not observed in women. Our findings suggest that higher, not lower, birth weight in males may contribute to less favourable cardiovascular autonomic regulation and potentially to an elevated cardiovascular risk in later life.

The associations of maternal body mass index with birthweight and placental weight. Does maternal diabetes matter? A population study of 106 191 pregnancies

INTRODUCTION

The aim of this study was to study whether the associations of maternal body mass index with offspring birthweight and placental weight differ by maternal diabetes status.

MATERIAL AND METHODS

We performed a population study of 106 191 singleton pregnancies by using data from the years 2009-2012 in the Medical Birth Registry of Norway. We estimated changes in birthweight and in placental weight (in grams) by maternal body mass index by linear regression analysis.

RESULTS

In pregnancies of women without diabetes, birthweight increased by 14.7 g (95% confidence interval 14.1-15.2) per unit increase in maternal body mass index, and the increase in placental weight was 4.2 g (95% confidence interval 4.0-4.4). In pregnancies of women with gestational diabetes, the corresponding figures were 11.8 g (95% confidence interval 8.3-15.4) and 2.9 g (95% confidence interval 1.7-4.0). In pregnancies of women with type 1 diabetes we found no significant changes in birthweight or in placental weight by maternal body mass index. Overall, mean birthweight was 513.9 g (95% confidence interval 475.6-552.1) higher in pregnancies involving type 1 diabetes than in pregnancies of women without diabetes. Mean placental weight was 102.1 g (95% confidence interval 89.3-114.9) higher. Also, in pregnancies of women with gestational diabetes, both birthweight and placental weight were higher than in women without diabetes (168.2 g and 46.5 g, respectively). Adjustments were made for maternal body mass index and gestational age at birth.

CONCLUSIONS

Birthweight and placental weight increased with increasing maternal body mass index in pregnancies of women without diabetes and in pregnancies of women with gestational diabetes, but not in pregnancies of women with type 1 diabetes. Independent of body mass index, mean birthweight and mean placental weight were highest in pregnancies of women with type 1 diabetes.

Utilizing Longitudinal Measures of Fetal Growth to Create a Standard Method to Assess the Impacts of Maternal Disease and Environmental Exposure

Impaired or suboptimal fetal growth is associated with an increased risk of perinatal morbidity and mortality. By utilizing readily available clinical data on the relative size of the fetus at multiple points in pregnancy, including delivery, future epidemiological research can improve our understanding of the impacts of maternal, fetal, and environmental factors on fetal growth at different windows during pregnancy. This study presents mean and standard deviation ultrasound measurements from a clinically representative US population that can be utilized for creating Z-scores to this end. Between 2006 and 2012, 18, 904 non-anomalous pregnancies that received prenatal care, first and second trimester ultrasound evaluations, and ultimately delivered singleton newborns at Brigham and Women's hospital in Boston were used to create the standard population. To illustrate the utility of this standard, we created Z-scores for ultrasound and delivery measurements for a cohort study population and examined associations with factors known to be associated with fetal growth. In addition to cross-sectional regression models, we created linear mixed models and generalized additive mixed models to illustrate how these scores can be utilized longitudinally and for the identification of windows of susceptibility. After adjustment for a priori confounders, maternal BMI was positively associated with increased fetal size beginning in the second trimester in cross-sectional models. Female infants and maternal smoking were associated with consistently reduced fetal size in the longitudinal models. Maternal age had a non-significant association with increased size in the first trimester that was attenuated as gestation progressed. As the growth measurements examined here are widely available in contemporary obstetrical practice, these data may be abstracted from medical records by investigators and standardized with the population means presented here. This will enable easy extension of clinical data to epidemiologic studies investigating novel maternal, fetal, and environmental factors that may impact fetal growth.