TitleEffects of maternally administered dexamethasone and acute hypoxemia at 0.7 gestation on blood pressure and placental perfusion in sheep.
Publication TypeJournal Article
Year of Publication2004
AuthorsKutzler, MA, Coksaygan, TC, Ferguson, AD, Nathanielsz, PW
JournalHypertens Pregnancy
Volume23
Issue1
Pagination75-90
Date Published2004
ISSN1064-1955
KeywordsAcute Disease, Animals, Blood Gas Analysis, Blood Pressure, Dexamethasone, Disease Models, Animal, Female, Glucocorticoids, Hypoxia, Maternal-Fetal Exchange, Oxygen, Perfusion, Placenta, Pregnancy, Pregnancy Complications, Pregnancy Trimesters, Regional Blood Flow, Sheep, Vascular Resistance
Abstract

Glucocorticoid administration to women in premature labor significantly decreases preterm infant morbidity and mortality. Fetal exposure to maternally administered glucocorticoids in late gestation causes fetal hypertension. We determined the effects of a single course (4 injections at 12-hr intervals) of dexamethasone (DM; 2 mg, a weight-adjusted dose equivalent to one-third the dose administered to pregnant women) or saline (S) in sheep at 103-104 days of gestation (dGA; term 149 dGA) on maternal and fetal blood pressure (BP). We also determined the BP and placental perfusion effects of acute maternal hypoxemia. Venous and arterial catheters were placed in 10 ewes and fetuses (DM = 6, S = 4) at 96 +/- 1 dGA. Maternal and fetal placental perfusion was determined with fluorescent microspheres. Dexamethasone increased fetal but not maternal BP; maternal and fetal placental blood flow and vascular resistance (VR) were unchanged. At 105 dGA, hypoxemia was induced for 1 hr by maternal nitrogen gas inhalation to decrease fetal PaO2 by 40%. Hypoxemia increased BP in DM but not S fetuses or mothers in either group. Hypoxemia decreased maternal placental blood flow by 39 +/- 7% and 51 +/- 9% and increased maternal placental VR by 65 +/- 7% and 69 +/- 6% in S and DM mothers, respectively. Hypoxemia did not alter fetal placental blood flow or VR in either treatment group. In summary, at 0.7 gestation, DM induces a hypertensive response to fetal hypoxemia that is characteristic of older fetuses but does not alter hypoxemia-induced reductions in maternal placental blood flow.

DOI10.1081/PRG-120028283
Alternate JournalHypertens Pregnancy
PubMed ID15117602
Grant ListF32 HL68393 / HL / NHLBI NIH HHS / United States
P01 HD21350 / HD / NICHD NIH HHS / United States
R01 HL055416 / HL / NHLBI NIH HHS / United States