The process whereby a fertilized egg develops into more than 200 different cell types and forms a new individual is both intriguing and fundamental to developmental biology. The systematic pathway of cellular differentiation is generally thought to confer a restriction whereby differentiated cells lose the capacity to change into other cell types. However, the substitution of nuclear material from one cell type (egg) with that of another, in a process known as nuclear transfer or cloning, can reverse this restriction by removing epigenetic modifications to the chromatin structure. The ability to clone new individuals using this procedure was achieved some 30 years ago in amphibia in an effort to understand cellular differentiation. More recently, with the advent of improved embryo micromanipulation techniques, the technology has been applied to domestic and laboratory animals.

Erectile dysfunction (formerly known as impotence) is defined as the consistent inability to achieve or maintain an erection suitable for intercourse. Until recently, most of the information on the prevalence of erectile dysfunction has been based on small studies of selected population samples. More reliable data became available with the completion of the Massachusetts Male Aging Study. Data from this study indicate that erectile dysfunction is a common condition with an estimated incidence rate of 26 cases per 1000 man-years. In 1993, the National Institutes of Health Consensus Conference estimated that 10 to 20 million men in the USA have problems with erection.

Ectopic pregnancy occurs when the conceptus implants outside the normal site within the uterine cavity. The most common site is within the Fallopian tube (98.3%), followed by abdominal (1.4%), ovarian (0.15%) and cervical (0.15%) implantation. Considering tubal ectopic pregnancies, 80% occur at the ampulla and 12% at the isthmus; 6% are fimbrial and 2% are interstitial. Approximately 5% to 5.7% of all clinical pregnancies from assisted reproductive technology (ART) in 1988–92 were ectopic; however, in 1995 the incidence was less at 2.8%. A meta-analysis of risk factors that predispose to ectopic pregnancy is depicted in Table 1. However, this meta-analysis does not control for the interplay of risk factors (multivariate analysis), including the impact of control group data and consequent problems of data collection (e.g. the incidence of pelvic inflammatory disease (PID) in the ectopic group is laparoscopically derived whereas it is derived from the history in the control group).

Ovarian stimulation protocols applied world-wide today may take several weeks per stimulated cycle, are complex, expensive and associated with a certain degree of risk. Gonadotrophin preparations are administered to stimulate multiple follicle development usually at daily doses of 150–300 IU (and sometimes higher) for one to three weeks. A premature rise in serum luteinizing hormone (LH) levels, generally believed to be detrimental for in vitro fertilization (IVF) outcome, is prevented by the co-administration of a gonadotrophin-releasing hormone (GnRH) agonist. This is usually initiated in the preceding cycle to allow for pituitary downregulation to occur before the initiation of exogenous follicle-stimulating hormone (FSH). Finally, the resumption of oocyte meiotic maturation is induced by a single bolus injection of human chorionic gonadotrophin (hCG) during the late follicular phase. In addition, the corpus luteum is supported during the luteal phase by repeated administration of hCG or supplemented by exogenous progesterone.