When pituitary growth hormone (GH) is released, blood glucose levels rise in non-pregnant women. The rise is termed the Dawn Phenomenon. Placental GH suppresses pituitary GH, so the rise in blood glucose should not occur in pregnant women. Researchers from Western Reserve University recently concluded that a rise in GH is noted in pregnant women, but that rise does not cause an increase in blood glucose. The findings were published in an April 2013 edition of AJOG (American Journal of Obstetrics and Gynecology).
Twenty women with no known glucose tolerance issues (all pregnant with singletons) were admitted to the hospital for one night. The women were between 28 weeks and 36 weeks pregnant at the time of admission. GH and insulin levels were monitored from 8 P.M. to 8 A.M. in two-hour intervals.
The Dawn Phenomenon causes a rise in blood glucose between 4 A.M. and 8 A.M. in non-pregnant women. Pregnant women show no increase in insulin or glucose levels during this time.
Source: Mandujano A, Thomas A, Presley L, Amini SB, Mouzon SH, Catalano PM. Does the dawn phenomenon have clinical relevance in normal pregnancy? Am J Obstet Gynecol. 2013 Apr 9. pii: S0002-9378(13)00355-4. doi: 10.1016/j.ajog.2013.04.006.