Lung function, arterial pressure and growth in sheep during early postnatal life following single and repeated prenatal corticosteroid treatments.
BACKGROUND
Antenatal corticosteroid therapy is of great benefit to preterm infants, owing largely to effects on lung maturation. In sheep, repeated betamethasone injections given to the ewe improve lung function following preterm birth but also cause intrauterine growth restriction (IUGR). In humans and in animal models, IUGR is associated with impaired postnatal lung function. The effects on lung function of repeated prenatal betamethasone treatments and associated IUGR following term delivery are unknown. AIM AND STUDY DESIGN: To determine the effects of antenatal betamethasone treatments on postnatal arterial pressure, blood gases, ventilation, pulmonary gas volumes and compliance in serial studies of four groups of lambs until 4 weeks of age.


METHODS
Treatment groups were (1) maternal injections of saline at 104, 111 and 118 days of gestation, (2) a single maternal injection of betamethasone (0.5 mg/kg) at 104 days followed by saline at 111 and 118 days, (3) repeated betamethasone injections at 104, 111 and 118 days, or (4) no intervention (term is approximately 150 days).


RESULTS
Repeated maternal betamethasone injections reduced birthweight and resulted in reduced postnatal body weights and arterial pressure throughout the first postnatal month. Lung function was not deleteriously affected by single or repeated maternal betamethasone treatments: blood gases, minute ventilation, lung volumes and compliance were not different between groups of lambs.


CONCLUSIONS
The absence of alterations in postnatal blood gases contrasts with other models of IUGR in sheep and suggests that changes in lung structure caused by betamethasone may benefit IUGR neonates born at term.
Moss
Timothy J M
TJ
Department of Obstetrics and Gynaecology, The University of Western Australia, 35 Stirling Highway, WA, 6009 Crawley, Australia. tmoss@cyllene.uwa.edu.au
Harding
Richard
R
Newnham
John P
JP
D000305:Adrenal Cortex Hormones / Q000008:administration & dosage* / Q000009:adverse effects; D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001623:Betamethasone / Q000008:administration & dosage / Q000009:adverse effects; D001724:Birth Weight / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects*; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D005333:Fetus / Q000187:drug effects*; D005865:Gestational Age; D006863:Hydrogen-Ion Concentration; D008168:Lung / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012123:Pulmonary Ventilation; D012756:Sheep
D000305:Adrenal Cortex Hormones; D002245:Carbon Dioxide; D001623:Betamethasone; D010100:Oxygen