Coexistent hemoconcentration and hypoosmolality during superovulation and in severe ovarian hyperstimulation...

To investigate the concomitant time courses of the changes in osmolality and calculated blood volume during the genesis of ovarian hyperstimulation syndrome (OHSS).

Prospective longitudinal study.

IVF-ET program in a university-based assisted reproductive technology center.

Thirty women undergoing superovulation for IVF-ET.

Blood and urine samples were obtained on seven occasions from the start of FSH stimulation until a pregnancy test. Five women with severe OHSS had daily blood and urine tests during hospitalization.

Changes in serum and urine osmolality, serum electrolytes, albumin, hemoglobin, and hematocrit.

Blood volume in women with OHSS decreased significantly by 20% from days hCG +2 to +4, followed by a sustained increase of 30% above baseline from days hCG +8 to +12. There was no statistically significant change in blood volume in women without OHSS. There was a sharp decrease in serum osmolality in women without OHSS between days 0 and hCG +2, which recovered toward baseline from day 4 after hCG. In women with OHSS, there was an unexpected increase in osmolality of 6 mOsm/kg between days hCG -2 and 0, followed by a decrease of 8 mOsm/kg by day hCG +2; this was sustained until day hCG +12. Patients with OHSS demonstrated a concentration and dilution of their urine during the acute and recovery phases of the syndrome, respectively, despite persistence of the hypoosmolar state.

Decreased osmolality in severe OHSS is maintained despite significant decreases and increases in blood volume, suggestive of fundamental alterations in osmoregulation.