Published online by Cambridge University Press: 22 October 2009
The primary aim of an IVF treatment cycle is the creation of two ‘good quality’ pre-embryos for transfer, with a secondary aim of additional embryos for cryo-preservation. Because of the need for sufficient oocytes for fertilization, and embryos for selection, it is necessary to stimulate sufficient follicles to generate an adequate number of mature oocytes. Recent advances towards the transfer of one or two blastocysts for transfer, sometimes after blastomere biopsy and aneuploidy screening, also requires a sufficient number of oocytes for fertilization.
Primordial follicle recruitment is determined by factors that are still to be fully determined and is independent of follicle stimulating hormone (FSH) stimulation. In a given cycle an individual woman has a certain number of follicles that will be sensitive to FSH – the main determinants being a combination of her chronological age and ovarian age (‘ovarian reserve’). There are a number of tests of ovarian reserve, which may be used singly or in combination to predict ovarian response and gonadotrophin dosage: baseline serum concentrations (FSH, inhibin, oestradiol), ovarian stimulation/challenge tests and ultrasonography (ovarian volume, primordial follicle number and blood flow).
There are a large number of regimens for superovulation in IVF protocols. The evolution of superovulation strategies has encompassed the development of new classes of drugs and has lead to improved efficiency of the treatment cycle. This chapter will outline the current options, concentrating on evidence for clinical effectiveness. Complications of treatment, such as ovarian hyperstimulation syndrome (OHSS), are dealt with elsewhere in this book.