Longer ovarian stimulation reduces embryo number and clinical pregnancy rate in long GnRH agonist cycles.
BACKGROUND
The aim of this study was to analyze whether the length of controlled ovarian stimulation affects in vitro fertilization (IVF) cycle outcomes.


METHODS
This retrospective cohort study was performed at a private, university-affiliated fertility centre. We reviewed 1522 IVF cycles, comprising 979 long gonadotropin-releasing hormone (GnRH) agonist and 543 GnRH antagonist protocols. All subjects underwent controlled ovarian stimulation followed by fresh embryo transfer. Logistic regression analysis was used to examine the relationship between trigger day and the following cycle outcomes: normal fertilization rate (FR), proportion of mature oocytes, proportion of cycles with embryos for cryopreservation, and clinical pregnancy rate (CPR).


RESULTS
In long agonist cycles, having more days of stimulation was associated with a lower clinical pregnancy rate (OR=0.87, 95% CI=0.80-0.96, P=0.01). Longer stimulation also resulted in fewer cycles with supernumerary embryos for cryopreservation (OR=0.84, 95% CI=0.77-0.92, P=0.0005), despite a having greater number of mature oocytes retreived (OR=1.05, 95% CI=1.01-1.10, P=0.04). For each additional day of stimulation in a long agonist protocol, the odds of achieving a clinical pregnancy were reduced by 13% and of achieving cryopreservation by 16%. In the antagonist protocol group, the length of ovarian stimulation did not have an effect on the clinical pregnancy and cryopreservation rates.


CONCLUSIONS
Longer duration of ovarian stimulation appears to reduce clinical pregnancy and embryo cryopreservation rates in subjects undergoing long GnRH agonist cycles. The number of days of stimulation does not appear to affect those using the GnRH antagonist protocol.
University of British Columbia, Division of Reproductive Endocrinology and Infertility, Vancouver, Canada - caitlin.dunne@alumni.ubc.ca.|Pacific Centre for Reproductive Medicine, Burnaby, Canada - caitlin.dunne@alumni.ubc.ca.
Caitlin
C
Dunne
Pacific Centre for Reproductive Medicine, Burnaby, Canada.
Carole
C
Lawrence
Women's Health Research Institute, British Columbia Women's Hospital, Vancouver, Canada.
Arianne
A
Albert
University of British Columbia, Division of Reproductive Endocrinology and Infertility, Vancouver, Canada.|Pacific Centre for Reproductive Medicine, Burnaby, Canada.
Jon C
JC
Havelock
D000328:Adult; D015331:Cohort Studies; D015925:Cryopreservation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D007987:Gonadotropin-Releasing Hormone / Q000819:agonists / Q000037:antagonists & inhibitors; D006801:Humans; D016015:Logistic Models; D009865:Oocytes; D010062:Ovulation Induction / Q000379:methods*; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D013997:Time Factors; D055815:Young Adult
D007987:Gonadotropin-Releasing Hormone