Maternal Corticotropin-Releasing Hormone Levels during Pregnancy and Offspring Adiposity

Authors

  • Matthew W. Gillman,

    Corresponding author
    1. Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
    2. Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts
    Search for more papers by this author
  • Janet W. Rich-Edwards,

    1. Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
    2. Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts
    Search for more papers by this author
  • Susanna Huh,

    1. Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
    2. Children's Hospital Boston, Boston, Massachusetts.
    Search for more papers by this author
  • Joseph A. Majzoub,

    1. Children's Hospital Boston, Boston, Massachusetts.
    Search for more papers by this author
  • Emily Oken,

    1. Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
    Search for more papers by this author
  • Elsie M. Taveras,

    1. Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
    Search for more papers by this author
  • Sheryl L. Rifas-Shiman

    1. Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Massachusetts
    Search for more papers by this author

Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, 133 Brookline Avenue, Sixth Floor, Boston, MA 02215. E-mail: matthew_gillman@hms.harvard.edu

Abstract

Objective: Animal models suggest that fetal exposure to glucocorticoids can program adiposity, especially central adiposity, later in life. We examined associations of maternal corticotropin-releasing hormone (CRH) levels in the late 2nd trimester of pregnancy, a marker of fetal glucocorticoid exposure, with child adiposity at age 3 years.

Research Methods and Procedures: We analyzed data from 199 participants in Project Viva, a prospective cohort study of pregnant women and their children, At age 3 years, the main outcomes were age-sex-specific BMI z score and the sum of subscapular (SS) and triceps (TR) skinfold thicknesses to represent overall adiposity, and ratio of SS to TR (SS:TR) to represent central adiposity.

Results: Mean (standard deviation) maternal 2nd trimester log CRH was 4.94 (0.56) pg/mL. At age 3, mean (standard deviation) for BMI z score was 0.52 (1.02); for SS + TR, 16.51 (3.94) mm; and for SS:TR, 0.67 (0.17). Log CRH was mildly inversely correlated with birth weight (r = −0.08), chiefly because of its association with length of gestation (r = −0.21) rather than fetal growth (r = −0.004). After adjustment for sociodemographic factors, maternal smoking, BMI, and gestational weight gain, fetal growth, length of gestation, breastfeeding duration, and (for SS:TR only) child's 3-year BMI, each increment of 1 unit of log CRH was associated with a reduction in BMI z score [−0.43; 95% confidence interval (CI), −0.73, −0.14; p = 0.004] and possible reduction in SS + TR (−1.10; 95% CI, −2.33, 0.14; p = 0.08). In contrast, log CRH was associated with higher SS:TR (0.07; 95% CI, 0.02, 0.13; p = 0.007).

Discussion: Fetal exposure to glucocorticoids, although associated with an overall decrease in body size, may cause an increase in central adiposity.

Introduction

Obesity is at epidemic proportions in the developed world and is emerging as a prime threat to health in the developing world. Increases in overweight in the past 2 to 3 decades are evident at all ages, including during infancy (1, 2). Thus, the imperative to prevent obesity and its consequences reaches to the earliest stages of human development, even before birth.

Much of the epidemiological evidence for the fetal origins of obesity relies on birth weight (BW),1 which is easily measured but is a poor proxy for in utero determinants (3). Higher BW is associated with higher BMI in childhood or adulthood, whereas after adjusting for attained body size, lower BW is associated with central obesity and its concomitants, including the metabolic syndrome (4).

One potential explanation for the observed associations between lower BW and central obesity is the effect of fetal exposure to glucocorticoids. In animal models, investigators have experimentally increased fetal exposure to glucocorticoids through transgenic models (5), by exogenous administration of dexamethasone (6, 7, 8), or by altering maternal diet to decrease the activity of the placental enzyme that deactivates corticosterone (cortisol in the human) to 11-dehydrocorticosterone (cortisone) (6, 9). In these experiments, the offspring have reduced weight, but not necessarily adiposity, at birth. Later in life, they demonstrate increased adiposity, chiefly visceral adiposity, components of the metabolic syndrome including insulin resistance, glucose intolerance, and hypertension, and alterations in the hypothalamic-pituitary-adrenal (HPA) axis (5, 6, 7, 8, 9).

In humans, lower BW appears to be associated with increased cortisol levels in adulthood (10, 11). Among infants born small for gestational age (GA), percentage body fat is elevated, and alterations of glucose metabolism may be evident in the first few days of life (12, 13). One small study showed that both prematurity and reduced fetal growth, the two components of lower BW, were related to decreased insulin sensitivity in mid-childhood (14).

Given this chain of evidence, it is plausible that excess fetal exposure to glucocorticoid programs increased relative adiposity and central adiposity. Human data to address this hypothesis, however, are scant. Follow-up studies of children and adolescents whose mothers were administered betamethasone prenatally have not indicated changes in BMI, but study samples were small (15, 16, 17). Further, prenatal administration of glucocorticoids is limited to mothers at high risk of preterm birth; therefore, results may not be generalizable.

The purpose of this study was to examine the associations of plasma levels of corticotropin-releasing hormone (CRH) in the late 2nd trimester of pregnancy, a marker of fetal exposure to glucocorticoids, with adiposity-related outcomes at the age of 3 years in a prospective prebirth cohort study.

Research Methods and Procedures

Study Sample

Study subjects were a subset of participants in Project Viva, a prospective cohort study of pregnant women and their singleton children to study pre- and perinatal determinants of offspring health. We have reported previously details of recruitment and follow-up through pregnancy (18). Of the 2128 mother-infant pairs in the cohort, we obtained maternal 2nd trimester plasma CRH levels from 444, chosen to oversample black participants for a previous analysis of CRH and pregnancy outcomes (Rich-Edwards JW, Strong EF, Gillman MW, unpublished data). Of these 444, we excluded three with invalid CRH data, 11 whose babies were born before 34 weeks gestation, and 97 who did not provide consent for child follow up. Of the remaining 333, nine refused the 3-year visit, and 99 offspring had not yet reached age eligibility for the 3-year visit. On an additional 26 children assessed at age 3, we did not obtain all anthropometric outcomes, leaving 199 participants for analysis. We obtained informed consent from all mothers. Institutional review boards of participating institutions approved the study. All procedures were in accordance with the ethical standards for human experimentation established by the Declaration of Helsinki.

Measurements

We performed in-person study visits with the mother at the end of the 1st and 2nd trimesters of pregnancy and with both mother and child immediately after delivery and at 6 months and 3 years postpartum. Participants completed mailed questionnaires at 1 and 2 years postpartum. Using a combination of questionnaires and interviews, we collected information about a range of sociodemographic factors, lifestyle habits, and medical and reproductive history (18). Mothers reported paternal weight and height. We calculated gestational weight gain as the prepregnancy weight subtracted from the last clinically recorded weight before delivery. We obtained infant BW from the hospital clinical record and calculated GA from the last menstrual period; if the estimate of GA from the 2nd trimester ultrasound differed by >10 days, we used it instead. We determined BW-for-GA z value (fetal growth) by use of U.S. national reference data (19).

Exposure Variable

The main exposure variable was plasma concentration of CRH from blood samples we obtained at 26 to 28 weeks of gestation. Maternal 2nd trimester CRH level is a reasonable proxy for fetal glucocorticoid exposure for two reasons. First, virtually all maternal CRH during mid- to late gestation is derived from the placenta (20, 21). Second, in contrast to the cortisol-CRH feedback loop in the HPA axis, CRH and cortisol participate in a feed-forward loop within the maternal-placental-fetal unit. Thus, higher CRH levels cause higher cortisol production, which likely leads to increased fetal cortisol exposure (21).

After storage of samples at −80 °C, we assayed CRH with our previously described method (20). We have previously shown that CRH measurement is robust to the transport, processing, and storage protocols of epidemiological studies in which blood is drawn in the field (22). CRH levels were inversely related to length of gestation in this cohort (see Results), confirming others’ data (23, 24), providing additional support for the validity of our CRH measures.

Outcome Variables

At the 3-year visit, trained research staff measured weight with a Seca scale (model 881; Seca, Hanover, MD), height with Shorr height board (Shorr Productions, Olney, MD), and subscapular (SS) and triceps (TR) skinfold thicknesses with a Holtain caliper (Holtain Ltd., Crosswell, Crymych, Dyfed Wales, UK). Every 6 months, an expert auxologist (Irwin Shorr, MPH) trained or retrained the research staff in all anthropometric measurements among volunteer participants of ages similar to Viva participants. In these trainings, estimates of inter- and intra-observer reliability were satisfactory. Experienced field supervisors provided ongoing quality control by observing and correcting measurement technique every 3 months. At the 3-year time-point, we also measured child's blood pressure five times at 1-minute intervals using a Dinamap (GE Healthcare, Little Chalfont, Buckinghamshire, UK) Pro 100 oscillometric recorder and maternal height, weight, and blood pressure.

Data Analyses

From height and weight, we calculated BMI (kilograms per meter squared) and then each child's age- and sex-specific BMI z score by use of U.S. national reference data. We used the sum of skinfolds (SS + TR) to estimate overall adiposity and the ratio of skinfolds (SS:TR) to estimate central adiposity. Because the distribution of CRH concentration was skewed, we expressed our main exposure variable as log CRH.

We first examined 3-year adiposity outcomes by quartiles of log CRH level. In multivariate linear models, we used log CRH either as a categorical (quartiles) or a continuous variable. In our base model, we adjusted for age, sex, and race. In our subsequent models, we additionally adjusted for sociodemographic, and then physiological and anthropometric, covariates that were associated with either exposure or outcome in our data. Because we were interested in fat distribution after controlling for overall body size, we further adjusted for child's BMI z score in our analyses of SS:TR. For the continuous log CRH variable, we report linear regression estimates for a 1-unit increment in log CRH concentration. We used SAS version 8.2 (SAS Institute, Cary, NC) for all analyses.

Results

The mean age (range) of participants was 3.2 (2.8 to 4.0) years; 51% were females; 76% were white and 24% black or African-American. Reflective of a generally employed and insured managed care population, relatively few women had less than a high school education or had annual household incomes below $40,000 (Table 1). Compared with other white and black cohort children who had reached the 3-year time-point but whose mothers did not have CRH measurements, children in this analysis did not differ materially in household income, weight, height, BMI z score, or skinfold thicknesses. Because of the sampling criteria for CRH determination, there was a higher proportion of black participants (24% v. 8%), and participating mothers had lower educational attainment (11% v. 4% with no more than a high school education).

Table 1.  Characteristics of participants by quartiles of maternal late 2nd trimester log CRH concentration; data from 199 mothers and children participating in Project Viva
 Log CRH quartile 
 Quartile 1Quartile 2Quartile 3Quartile 4p*
  • CRH, corticotropin-releasing hormone; SD, standard deviation; BW, birth weight; GA, gestational age; SS, subscapular; TR, triceps.

  • *

    χ2 p value for categorical variables and ANOVA p values across quartiles for continuous variables.

 Mean (SD)
Log CRH (pg/mL)4.26 (0.26)4.75 (0.09)5.09 (0.10)5.66 (0.33) 
Maternal and paternal characteristics     
 Maternal age at enrollment (years)32.1 (5.4)32.5 (4.1)33.6 (4.2)32.6 (5.7)0.48
 Maternal prepregnancy BMI (kg/m2)25.4 (7.0)24.2 (3.7)25.0 (6.7)24.1 (5.2)0.64
 Maternal BMI at 3-year visit (kg/m2)26.5 (7.6)25.7 (4.4)26.4 (6.8)25.6 (5.5)0.83
 Maternal gestational weight gain (kg)15.2 (6.4)16.5 (5.8)16.3 (4.4)14.4 (5.6)0.21
 Paternal BMI (kg/m2)27.5 (4.4)26.8 (4.0)26.0 (4.0)26.3 (4.3)0.30
 N (column %)
Maternal race    0.02
 Black or African-American17 (35)15 (30)11 (22)5 (10) 
 White32 (65)35 (70)39 (78)45 (90) 
Household income at 3-year visit    0.41
 <$40,0009 (18)8 (16)3 (6)7 (14) 
 $40,001 to $70,00012 (24)7 (14)11 (22)5 (10) 
 $70,001 to $100,0007 (14)8 (16)14 (28)11 (22) 
 $100,001 to $150,00010 (20)17 (34)8 (16)12 (24) 
 >$150,0007 (14)6 (12)9 (18)11 (22) 
 Don't know/missing4 (8)4 (8)5 (10)4 (8) 
Education    0.10
 <High school7 (14)3 (6)4 (8)7 (14) 
 Some college13 (27)10 (20)5 (10)7 (14) 
 Bachelor of Arts or Bachelor of Science19 (39)19 (38)27 (54)15 (30) 
 Graduate degree10 (20)18 (36)14 (28)21 (42) 
Pregnancy smoking status    0.09
 Never34 (71)31 (63)34 (72)26 (54) 
 Quit before pregnancy12 (25)11 (22)12 (26)13 (27) 
 Smoked during pregnancy2 (4)7 (14)1 (2)9 (19) 
Marital status at 3-year visit    0.6
 Married or co-habitating43 (90)44 (92)41 (89)48 (96) 
 Divorced/separated/never married/other5 (10)4 (8)5 (11)2 (4) 
Parity    0.41
 025 (51)25 (50)21 (42)25 (50) 
 115 (31)21 (42)20 (40)17 (34) 
 28 (16)3 (6)4 (8)6 (12) 
 3+1 (2)1 (2)5 (10)2 (4) 
Infant characteristics     
 Sex    0.81
  Girl22 (45)27 (54)26 (52)26 (52) 
  Boy27 (55)23 (46)24 (48)24 (48) 
 BW (kg)3.43 (0.51)3.60 (0.44)3.62 (0.44)3.33 (0.59)0.01
 BW for GA (z value)0.09 (0.94)0.25 (0.80)0.44 (0.86)0.07 (0.96)0.13
 GA at delivery (weeks)39.4 (1.7)40.2 (1.2)39.6 (1.5)38.7 (2.0)<0.0001
 Breastfeeding duration (months)7.4 (4.4)6.8 (4.8)6.3 (4.3)7.1 (4.5)0.68
Child characteristics at 3-year visit     
 Age (months)38.3 (1.6)38.3 (2.1)38.1 (1.9)38.5 (2.4)0.76
 Child 3-year height (cm)97.6 (3.8)96.6 (3.9)96.8 (3.8)97.0 (4.2)0.62
 BMI (kg/m2)16.9 (2.0)16.6 (1.3)16.6 (1.1)16.3 (1.3)0.18
 BMI zscore0.71 (1.20)0.54 (0.91)0.54 (0.80)0.29 (1.10)0.26
 SS + TR (mm)16.6 (3.8)16.8 (4.6)15.9 (3.4)16.7 (3.9)0.71
 SS:TR (mm)0.68 (0.16)0.64 (0.14)0.66 (0.19)0.69 (0.19)0.46

The mean (standard deviation, range) of log CRH levels was 4.94 pg/mL (0.56, 3.00 to 6.78). At age 3, mean (standard deviation) for BMI was 16.6 (1.4); for BMI z score, 0.52 (1.02); for sum of SS + TR, 16.51 (3.94) mm; and for SS:TR, 0.67 (0.17). Log CRH had a small, negative correlation with BW (r = −0.08), chiefly due to its association with length of gestation (r = −0.21) rather than with fetal growth (r = −0.004) (Table 2). Fetal growth was substantially correlated with 3-year BMI z score (r = 0.19) but not with skinfold measurements (Table 2).

Table 2.  Unadjusted Pearson correlation coefficients among maternal late 2nd trimester log CRH concentration, birth size, and 3-year adiposity outcomes; data from 199 mothers and children participating in Project Viva
 Maternal log CRHBW/GA z scoreGA at birth3-year BMI z score3-year SS + TR3-year SS:TR
  1. CRH, corticotropin-releasing hormone; BW, birth weight; GA, gestational age; SS, subscapular; TR, triceps.

Maternal log CRH1−0.004−0.21−0.14−0.040.005
BW/GA zscore 10.230.19−0.030.06
GA at birth  1−0.001−0.08−0.05
3-year BMI zscore   10.470.11
3-year SS + TR    10.02
3-year SS:TR     1

In multivariate models, CRH levels were inversely associated with 3-year BMI z score. The fully adjusted model shows that for every unit increment in log CRH, BMI z score was −0.43 (−0.73, −0.14; p = 0.004) lower (Table 3). The sum of SS + TR was slightly lower with higher CRH levels, but the confidence interval (CI) was too wide to make a strong inference (effect estimate, −1.10 mm; 95% CI, −2.33, 0.14; p = 0.08). In contrast, CRH level was directly related to SS:TR; the higher the CRH level, the higher was this measure of central obesity (effect estimate, 0.07; 95% CI, 0.02, 0.13; p = 0.007). Maternal CRH levels were not associated with 3-year systolic or diastolic blood pressure.

Table 3.  Changes in 3-year adiposity outcomes for each increase of 1 unit in maternal late 2nd trimester log CRH concentration; data from 199 mothers and children participating in Project Viva
 Estimate from linear regression (95% confidence interval)
Model covariatesBMI z scoreSS + TR (mm)SS:TR
  1. CRH, corticotropin-releasing hormone; GA, gestational age; SS, subscapular; TR, triceps.

1. Child age and sex, maternal race/ethnicity−0.25 (−0.52, 0.01)−0.59 (−1.63, 0.45)0.03 (−0.01, 0.08)
2. Model 1 + maternal marital status and education, household income−0.21 (−0.48, 0.05)−0.39 (−1.45, 0.66)0.04 (0.00, 0.09)
3. Model 2 + maternal BMI, smoking, and gestational weight gain, infant GA, BW-for-GA, breastfeeding duration, and (for SS:TR) child BMI zscore−0.43 (−0.73, −0.14)−1.10 (−2.33, 0.14)0.07 (0.02, 0.13)

Figure 1 shows the associations of BMI z score and SS:TR with quartiles of log CRH. Like the analysis with continuous log CRH, they show the same contrast in direction between these two outcomes. Although the inverse association with BMI z score appears linear and monotonic, the direct association with SS:TR appears to be explained to a considerable degree by the influence of the top fourth of log CRH concentration.

Figure 1.

BMI z score (left axis) and SS:TR (right axis) among 3-year-old children, by quartiles of maternal late 2nd trimester log CRH concentration. Estimates (with standard error bars) adjusted for sociodemographic factors, maternal smoking, BMI, gestational weight gain, BW-for-GA z score (fetal growth), length of gestation, breastfeeding duration, and (for SS:TR only) child's 3-year BMI z score. Data from 199 mother-child pairs participating in Project Viva.

Discussion

Our findings suggest that increased fetal exposure to glucocorticoids leads to a reduction in body size and, perhaps, in overall adiposity, but an increase in central distribution of fat. These results from a general population sample of humans are in accord with several animal experiments. In a transgenic mouse model, excess glucocorticoid to the fetus produces visceral adiposity and its concomitants, insulin resistance, diabetes, and high blood pressure (5). A well-characterized rat model shows that altered maternal diet during pregnancy decreases activity of the placental enzyme 11β-hydroxysteroid dehydrogenase, type 2, which is responsible for deactivating the active steroid corticosterone (cortisol in the human) to 11-dehydrocorticosterone (cortisone). Thus, the fetus is exposed to increased glucocorticoid, which results both in reduced BW and in adult adiposity, hypertension, and glucose intolerance, despite normal postnatal diet (6, 8, 9). Also in animal models, prenatal dexamethasone administration to the mother lowers BW and programs offspring fasting and postprandial hyperglycemia (6) and alterations in the HPA axis (7).

Consistent with these findings, in at least two human studies, lower BW was associated with increased cortisol levels in adulthood (10, 11). In addition, percentage body fat appears to be higher among infants who are born small for gestational age (12). These babies have evidence of altered glucose metabolism even in the first 48 hours of life (13), and small-for-gestational-age infants who exhibit rapid weight gain in infancy have elevated fasting insulin at 1 year compared with those with slower growth (25). Thus, it is possible that excess glucocorticoid exposure programs the fetal HPA axis, resulting in proclivity to central adiposity and its consequences as the child grows (26). In addition, it is possible that glucocorticoids may stimulate adipocyte differentiation at the expense of proliferation (27, 28, 29), explaining the observed reduction in overall adiposity with higher CRH levels.

Strengths of this study include a well-characterized prospective cohort with adequate control for a large set of both maternal and child potentially confounding variables. Our laboratory determinations of CRH concentrations and anthropometric measurements were of high quality. Limitations include a relatively small sample size and restriction of the analytic sample to blacks and whites only. No current technique allows direct assessment of fetal glucocorticoid exposure in humans. We used maternal 2nd trimester CRH levels as a reasonable proxy, based on inferences from maternal-placental-fetal physiology (20, 21). Although we did not measure abdominal or visceral adiposity directly with an imaging technique, skinfold ratios are good proxies for truncal fat distribution as determined by DXA in this age group (30).

Further research in this and other human cohorts is warranted to examine the extent to which fetal exposure to glucocorticoids is associated with components of the metabolic syndrome and to investigate the determinants of maternal CRH levels, including psychosocial stress.

Acknowledgments

We thank the Project Viva participants and staff. This work was supported by NIH (Grants HD 34568, HL 64925, HL 68041, HL 75504, and HD 44807), by the March of Dimes Foundation, by the Robert Wood Johnson Foundation, Children's Hospital General Clinical Research Center (Grant RR02172), and by the Harvard Pilgrim Health Care Foundation and Harvard Medical School. The funding agencies had no say in study design, data interpretation, or manuscript writing.

Footnotes

  • 1

    Nonstandard abbreviations: BW, birth weight; HPA, hypothalamic-pituitary-adrenal; GA, gestational age; CRH, corticotropin-releasing hormone; SS, subscapular; TR, triceps; CI, confidence interval.

  • The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Ancillary