Blood to the cornual area of the uterus is mainly supplied from the ovarian artery in the follicular phase and from the uterine artery in the luteal phase.

Background: The blood supply to the uterus is provided by the uterine and ovarian arteries, which form anastomoses. Yet the flow direction through this anastomoses and the primary source of blood supply to the tubes and uterine cornua remains unknown. To clarify this issue, we studied the spatial propagation of temperature changes following cooling of the upper vaginal area.

Methods: A thermocatheter with eight measurement points at 5-mm intervals was inserted into the uterus of nine women in the follicular phase and 11 in the luteal phase. The distal tip was positioned in the cornual area and temperatures were registered every 2 s. The vagina was then cooled for 7 min with 25 degrees C saline.

Results: The pattern of uterine cooling based on local counter-current transfer differed between the follicular and luteal phase. Cooling of the cornual area was significantly lower in the luteal phase compared with the follicular phase, indicating a shift in the prevailing source of arterial supply in that area following ovulation.

Conclusions: The divide between the territories irrigated by the uterine and ovarian arteries moves between the follicular and luteal phase. This constitutes the first description of a functionally determined shift in the territorial divide of two vascular systems, and has numerous practical implications.