National and regional usage
In the Nordic countries, letrozole is practically the standard initial regimen used for ovulation induction, since no formulation of clomifene is registered for use there.India banned the usage of letrozole in 2011, citing potential risks to infants. In 2012, an Indian parliamentary committee said that the drug controller office colluded with letrozoles makers to approve the drug for infertility in India. Technique
Although there are many possible additional diagnostic and interventional techniques, protocols for ovulation induction generally consist of:

Determining the first day of the last menstruation, which is termed day 1. In case of amenorrhea, a period can be induced by intake of an oral progestin for 10 days. Daily administration of the ovulation induction regimen, starting on day 3, 4, or 5, and it is usually taken for 5 days. Sexual intercourse or artificial insemination by the time of ovulation. Ultrasonography
During ovulation induction, it is recommended to start at a low dose and monitor the ovarian response with transvaginal ultrasound, including discernment of the number of developing follicles. Initial exam is most commonly started 4–6 days after last pill. Serial transvaginal ultrasound can reveal the size and number of developing follicles. It can also provide presumptive evidence of ovulation such as sudden collapse of the preovulatory follicle, and an increase in fluid volume in the rectouterine pouch. After ovulation, it may reveal signs of luteinization such as loss of clearly defined follicular margins and appearance of internal echoes.
A choriovitelline placenta is a placenta formed by the yolk sac and chorion. In a choriovitelline placenta, the yolk sac fuses with the chorion and, subsequently, wrinkles develop that hold the embryo to the uterine wall, thus forming the choriovitelline placenta. The chorionic blood vessels are connected with the vitelline blood vessel of the yolk sac. It is a primitive type of placenta found in all marsupials. (However, bandicoots also have a chorioallantoic placenta.) A choriovitelline placenta also forms early in the development of some placental mammals before the chorioallantoic placenta forms and the choriovitelline placenta is resorbed. == References ==