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

doi:10.1016/j.preghy.2014.03.028

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

Pregnancy Hypertens. 2014 Jul;4(3):238. doi: 10.1016/j.preghy.2014.03.028. Epub 2014 Jul 9.

Authors

L I Stirrat¹, J R O'Reilly¹, S C Riley¹, A F Howie¹, G J Beckett¹, R Smith¹, B R Walker¹, J E Norman¹, R M Reynolds¹

Affiliation

¹ Tommy's Centre for Maternal & Fetal Health, Queen's Medical Research Institute Edinburgh, United Kingdom.

PMID: 26104631
DOI: 10.1016/j.preghy.2014.03.028

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.