"Infertility is defined as the failure to achieve pregnancy after 12 months of regular unprotected sexual intercourse. Approximately 85% of infertile couples have an identifiable cause. The most common causes of infertility are , , and . The remaining 15% of infertile couples have “unexplained infertility.” Lifestyle and environmental factors, such as and , can adversely affect fertility. Ovulatory disorders account for approximately 25% of infertility diagnoses; 70% of women with anovulation have . Infertility can also be a marker of an underlying chronic disease associated with infertility. , s such as , and s are used to induce ovulation or for ovarian stimulation during (IVF) cycles. Adverse effects of gonadotropins include multiple pregnancy (up to 36% of cycles, depending on specific therapy) and ovarian hyperstimulation syndrome (1%-5% of cycles), consisting of ascites, electrolyte imbalance, and hypercoagulability. For individuals presenting with anovulation, ovulation induction with timed intercourse is often the appropriate initial treatment choice. For couples with unexplained infertility, , or mild male factor infertility, an initial 3 to 4 cycles of ovarian stimulation may be pursued; IVF should be considered if these approaches do not result in pregnancy. Because female fecundity declines with age, this factor should guide decision-making. Immediate IVF may be considered as a first-line treatment strategy in women older than 38 to 40 years. IVF is also indicated in cases of severe male factor infertility or untreated bilateral tubal factor."