Inappropriate fetal exposure to maternal glucocorticoid (GC) has been proposed as a mechanism for fetal programming where the effects of GC may be mediated by the placenta. However, the consequences of maternal GC on placental morphology and enzyme expression are unclear. Objectives: We used betamethasone (BET) to determine effects on placentome subtype distribution and expression of prostaglandin H synthase type 2 (PGHS-2) enzyme. Methods: Pregnant sheep carrying male fetuses were randomized to receive injections of saline (n = 30) or one (104 days of gestation, (dG); n = 6), two (104, 111 dG; n = 6) or three (104, 111, 118 dG; n = 11) doses of BET (0.5 mg/kg). Placental tissue was collected prior to (75, 84, 101 dG), during (109, 116 dG) and after BET (122, 132, 146 dG). Results: Total number of placentomes was not different between gestational ages. A- and B-subtypes were most affected by prenatal BET exposure; numbers of A-subtypes were increased and numbers of B-subtypes were decreased compared to controls at 116 dG. At term numbers of A-subtypes were lower after BET, but the weight range distribution was similar to controls. In controls, placental PGHS-2 protein levels increased with gestational age and PGHS-2 localized primarily to uninuclear trophoblast cells. After BET, PGHS-2 protein in C-subtypes at term was significantly increased compared to A-subtypes. Conclusions: Maternal BET treatment in late gestation affects the proportions of placentome subtypes and their differential expression of PGHS-2. Our data do not support previous hypotheses that A-subtypes develop into B-, C- and D-subtypes over the course of gestation.

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Department of Health Sciences

Braun, T. (T.), Li, S. (S.), Moss, T.J.M. (T. J.M.), Connor, K, Doherty, D.A. (D. A.), Nitsos, I. (I.), … Sloboda, D.M. (D. M.). (2011). Differential appearance of placentomes and expression of prostaglandin H synthase type 2 in placentome subtypes after betamethasone treatment of sheep late in gestation. Placenta, 32(4), 295–303. doi:10.1016/j.placenta.2011.01.012