Effect of coasting on IVF cycle characteristics and outcome in short vs. long GnRH agonist protocols.

AIMS: To compare the results of IVF cycles following coasting in patients treated with long versus short GnRH agonist protocols.

METHODS: A retrospective comparative study in which all women aged 35 years or less attending the IVF unit from 2000 to 2006 in whom coasting was used in GnRH agonist protocols were included. Data on coasting-related variables and outcome were collected from the files and compared between the short GnRH agonist (n = 78) and long GnRH agonist (n = 181) cycles.

RESULTS: The short GnRH agonist cycles were characterized by higher E2 levels during coasting and longer duration of coasting than the long GnRH agonist cycles. Although the number of retrieved oocytes was lower following coasting in the short protocol, there was no difference between the groups in fertilization rate, number of high-quality embryos available for transfer, and pregnancy rate. Pregnancy rate in both protocols was negatively correlated to E2 level at initiation of coasting. The overall moderate and severe OHSS rate after coasting was 5.1% in the short-protocol group and 6.0% in the long-protocol group (p = 0.76).

CONCLUSIONS: The ovarian response curve to coasting is longer in the short than in the long GnRH-agonist protocol, but there is no significant difference in pregnancy or OHSS rates.