To compare pregnancy rates with fresh and frozen embryo transfer in patients admitted to Royal Jubilee Maternity Service (RJMS), Belfast between January 1st 2004 and December 31st 2005 with ovarian hyperstimulation syndrome (OHSS).

A retrospective analysis of all ART cycles (2,283) carried out in RJMS between January 1st 2004 and December 31st 2005 and of all patients admitted to RJMS within 3 weeks of assisted reproduction therapy (ART).

The incidence of OHSS requiring admission was 2.01%, which represented 80.70% of post-ART emergency admissions. The eventual pregnancy rate was 52.27% in all women admitted with OHSS. The pregnancy outcome in OHSS patients who received fresh embryo transfer was 56.52% and with frozen embryo transfer 50%. The main indications for fertility treatment in OHSS cases were male factor (31%) and polycystic ovarian syndrome (14%). Two distinct incidence peaks of OHSS were identified – early and late. 77.77% of women who suffered from late onset OHSS had a concurrent positive pregnancy test.

The pregnancy rate in OHSS cases, both with fresh and subsequently with frozen embryo transfer, was exceptionally high. There was no statistically significant difference between fresh and frozen embryo transfer pregnancy rates. An elective embryo freezing policy to moderate the severity and duration of OHSS does not compromise outcome for women at risk of OHSS.