When clomiphene citrate (CC) is used for ovulation induction, endometrial thickness is often decreased compared with spontaneous cycles during and immediately following the days CC is taken, because of its antiestrogen effect. A triple-line pattern on the day of human chorionic gonadotropin (hCG) administration has been reported to be necessary for implantation in controlled ovarian hyperstimulation (COH) cycles, where human menopausal gonadotropin (hMG) or follicle stimulating hormone (FSH) is administered. A triple-line endometrial pattern on the day of hCG administration in in-vitro fertilization (IVF) cycles is related to serum estradiol level, the number of mature oocytes, and the number of top-quality embryos and is unrelated to serum progesterone levels. Preclinical miscarriage, also referred to as biochemical pregnancy, in which quantitative hCG levels initially indicate pregnancy but decrease before a gestational sac can be seen on ultrasound, and clinical miscarriage of embryos with karyotype is the result of inadequate endometrial development.