Accurate follicular monitoring of Controlled Ovarian Stimulation by transvaginal ultrasound is considered important for the success of human in vitro fertilization (IVF). The aim of this study is to evaluate the effect of timing oocyte maturation and egg collection on the basis of follicular measurements made automatically with Sono Automated Volume Calculation (SonoAVC) against those made with conventional 2D ultrasound in relation to the number of mature oocytes collected.

This study will take place in women undergoing IVF who are high responders (>=14 follicles>=11mm) and hence at risk for developing ovarian hyperstimulation syndrome (OHSS), treated with a GnRH antagonist protocol and administered GnRH agonist to trigger final oocyte maturation.

Accurate follicular monitoring of Controlled Ovarian Stimulation by transvaginal ultrasound is considered important for the success of human in vitro fertilization (IVF). Accurate assessment of the size of follicles is important for the timing of oocyte maturation and subsequent oocyte retrieval.

Serial assessment of follicle number and size is used routinely to assess the response to ovarian stimulation during assisted reproduction treatment (ART). Two-dimensional (2D) ultrasound is used to identify and scroll through each ovary while the observer quantifies the number of follicles present. An objective assessment of the size of the larger follicles, commonly those measuring >10 mm, is then made through a series of 2D measurements of their perceived mean diameter.

Sono Automated Volume Calculation (SonoAVC; GE Medical Systems) is a new software program that can be applied to datasets acquired with use of threedimensional (3D) ultrasound. It individually identifies and quantifies the size of any hypoechoic region within these 3D datasets, providing an automatic estimation of their absolute dimensions and volume. SonoAVC is an ideal and, potentially, a clinically important tool for the assessment and measurement of follicles during controlled ovarian stimulation because each hypoechoic area is individually color coded, thereby eliminating the possibility of measuring the same follicle more than once.

In women with high ovarian response to gonadotrophin stimulation, the accurate measurement of the number and size of follicles present in hyperstimulated ovaries is a challenge for clinicians and ultrasonographers.

The aim of this study is to evaluate the effect of timing final oocyte maturation trigger and egg collection on the basis of follicular measurements made automatically with SonoAVC against those made with conventional 2D ultrasound in relation to the number of mature oocytes collected. This study will include women undergoing ART who are high responders (presence of =>14 follicles>=11mm) and hence at risk for developing ovarian hyperstimulation syndrome (OHSS), treated with a GnRH antagonist protocol and are administered GnRH agonist to trigger final oocyte maturation. All resulting embryos (blastocysts) will be cryopreserved and transferred in a subsequent frozen cycle.

Inclusion Criteria:

• AMH >= 3ng/ml
• at least 14 follicles =>11 mm diameter on final day of stimulation
• undergoing GnRH antagonist protocol
• administered GnRH agonist to trigger final oocyte maturation

Exclusion Criteria:

• poor responders
• hCG injection to trigger final oocyte maturation

Women (patients), clinician performing oocyte retrieval and clinical embryologist will be blinded to the method used for monitoring follicle development