Differential effects of maternal and fetal betamethasone injections in late-gestation fetal sheep.
OBJECTIVE
To determine the effects of single or repeated intramuscular injections of betamethasone, given maternally or directly to the fetus, on chronically catheterized, late-gestation fetal sheep.


METHODS
Fetal or maternal sheep received either repeated intramuscular injections of betamethasone (0.5 mg/kg body weight at 104, 111, and 118 days' gestation), single betamethasone injection (at 104 days' gestation, followed by saline at 111 and 118 days' gestation), or repeated saline injections; n = 6 or 7 per group. At approximately 130 days' gestation fetuses were catheterized for serial measurements of heart rate, arterial pressure, blood gases, metabolites, and electrolytes.


RESULTS
Repeated maternal betamethasone injections reduced birth weight (P =.03) without fetal hypoxemia or hypoglycemia. Circulating fetal calcium and lactate concentrations were reduced (P =.002 and P =.014, respectively) by repeated maternal betamethasone only. Fetal hematocrit tended to be lower after fetal (P =.3) and maternal (P =.07) betamethasone.


CONCLUSIONS
Growth restriction caused by repeated maternal betamethasone treatments is not due to overt chronic placental insufficiency but may be caused by alterations in hormonal mediators of fetal growth or impairment of placental transport of specific nutrients.
Moss
Timothy J M
TJ
Lotteries Commission Perinatal Research Laboratories, School of Women's and Infants' Health, University of Western Australia, Box M094, 35 Stirling Highway, Crawley, WA 6009, Australia. tmoss@cyllene.uwa.edu.au
Nitsos
Ilias
I
Harding
Richard
R
Newnham
John P
JP
D000818:Animals; D001623:Betamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D001724:Birth Weight / Q000187:drug effects; D001784:Blood Gas Analysis; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000187:drug effects; D002118:Calcium / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005314:Embryonic and Fetal Development / Q000187:drug effects*; D005260:Female; D005312:Fetal Blood / Q000187:drug effects / Q000378:metabolism; D020567:Fetal Weight / Q000187:drug effects; D005865:Gestational Age; D005938:Glucocorticoids / Q000008:administration & dosage / Q000494:pharmacology*; D006340:Heart Rate, Fetal / Q000187:drug effects; D007273:Injections, Intramuscular; D007773:Lactates / Q000097:blood; D008168:Lung / Q000187:drug effects / Q000196:embryology; D018811:Maternal Exposure; D009929:Organ Size / Q000187:drug effects; D010920:Placenta / Q000187:drug effects; D011247:Pregnancy; D012756:Sheep
D001786:Blood Glucose; D005938:Glucocorticoids; D007773:Lactates; D001623:Betamethasone; D002118:Calcium