title: Maternal dexamethasone treatment in late gestation induces precocious fetal maturation and delivery in healthy Thoroughbred mares.
abstract: BACKGROUND
  The foal requires an active hypothalamo-pituitary-adrenal (HPA) axis for organ maturation and post natal survival. Prenatal administration of synthetic glucocorticoids may provide an effective method for inducing fetal maturation safely in the mare.
  
  
  OBJECTIVE
  To determine whether dexamethasone administered to late pregnant mares: 1) will induce fetal maturation and precocious delivery; 2) is safe to use and 3) to identify endocrine responses in the mare and foal.
  
  
  METHODS
  Pregnant Thoroughbred mares received either 100 mg dexamethasone i.m. (treated n = 5) or 50 ml saline i.m. (control n = 5) at 315, 316 and 317 days of gestation. Plasma progestagens, cortisol and prostaglandin F(2α) metabolite (PGFM) concentrations were measured before and after treatment. The foals were weighed, the crown-rump length (CRL) measured and an adrenal stimulation test performed on Day 1.
  
  
  RESULTS
  Dexamethasone significantly (P<0.01) reduced gestation length in treated mares without apparent adverse effects. Plasma progestagens increased (P<0.05), and cortisol and PGFM (P<0.05) decreased, following dexamethasone treatment compared with control mares. Foals were clinically mature but those from dexamethasone treated mares had reduced (P<0.05) CRL, but not bodyweights, compared with controls. Their cortisol concentrations increased following exogenous adrenocorticotrophic hormone stimulation but 2 foals from dexamethasone treated mares showed evidence of adrenal suppression.
  
  
  CONCLUSIONS
  Dexamethasone stimulates precocious fetal maturation and delivery in healthy late pregnant mares. However, fetal HPA activity may be suppressed.
  
  
  CONCLUSIONS
  Dexamethasone treatment could be used to improve foal viability in mares at risk of preterm delivery. The endocrine effects of such a therapy must be evaluated before clinical intervention with glucocorticoids can be recommended.
authors.affiliation: Department of Veterinary Medicine Equine Fertility Unit, University of Cambridge, Mertoun Paddocks, Newmarket, UK. jenny.ousey@rossdales.com
authors.forename: J C
authors.initials: JC
authors.lastname: Ousey
authors.forename: M
authors.initials: M
authors.lastname: Kölling
authors.forename: H
authors.initials: H
authors.lastname: Kindahl
authors.forename: W R
authors.initials: WR
authors.lastname: Allen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight / Q000502:physiology; D018568:Crown-Rump Length; D003907:Dexamethasone / Q000008:administration & dosage*; D015237:Dinoprost / Q000031:analogs & derivatives / Q000097:blood; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage*; D006736:Horses / Q000097:blood / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D010913:Pituitary-Adrenal System / Q000502:physiology*; D011247:Pregnancy; D011372:Progestins / Q000097:blood
chemical_list: D005938:Glucocorticoids; D011372:Progestins; C008228:15-keto-13,14-dihydroprostaglandin F2alpha; D003907:Dexamethasone; D015237:Dinoprost; D006854:Hydrocortisone