Altered maternal hypothalamic-pituitary-adrenal axis activity in obese pregnancy is associated with macrosomia and prolonged pregnancy

L I Stirrat, J R O'Reilly, S C Riley, A F Howie, G J Beckett, R Smith, B R Walker, J E Norman, R M Reynolds

Research output: Contribution to journalArticle (Academic Journal)

Abstract

BACKGROUND: The hypothalamic-pituitary-adrenal (HPA) axis is important for fetal growth and timing of parturition. Maternal obesity is associated with macrosomia (birthweight ⩾4000g) and prolonged pregnancy (⩾41weeks). We aimed to characterise HPA axis hormones in obese pregnancy and to test associations with these pregnancy outcomes.

METHOD: Fasting cortisol was measured by radioimmunoassay in venous blood at 16, 28 and 36 weeks of gestation in 286 obese (BMI 44.05±3.98kg/m(2)) and 137 lean (BMI 22.71±1.66kg/m(2)) pregnant women. In subsets (n=20 obese, 20 lean) we measured corticosteroid binding globulin (CBG) and CRH by radioimmunoassay; progesterone, estradiol (E2), estriol (E3) and sex-hormone-binding-globulin (SHBG) by ELISA; and albumin by bromocresol green binding. Free cortisol levels were calculated using Coolen's equation.

RESULTS: Cortisol, CBG, calculated free cortisol, CRH, E2, E3, progesterone and SHBG levels rose similarly during pregnancy in obese and lean, but were significantly lower in obese (p<0.05). In obese, lower free cortisol at 16 weeks was associated with higher birthweight (r=-0.46, p<0.05). Cortisol was not associated with labour onset. CRH was significantly lower at 36 weeks in women who delivered at ⩾41weeks and in women with macrosomic babies (p<0.05); and correlated negatively with gestation at delivery in obese (r=-0.557, p<0.05).

CONCLUSION: Our findings suggest that decreased HPA axis activity in obese pregnancy may be a mechanism underlying macrosomia and prolonged pregnancy.

Original languageEnglish
Pages (from-to)238
JournalPregnancy Hypertension
Volume4
Issue number3
DOIs
Publication statusPublished - Jul 2014

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Copyright © 2014.

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    Stirrat, L. I., O'Reilly, J. R., Riley, S. C., Howie, A. F., Beckett, G. J., Smith, R., Walker, B. R., Norman, J. E., & Reynolds, R. M. (2014). Altered maternal hypothalamic-pituitary-adrenal axis activity in obese pregnancy is associated with macrosomia and prolonged pregnancy. Pregnancy Hypertension, 4(3), 238. https://doi.org/10.1016/j.preghy.2014.03.028