Letrozole is often utilized as a fertility drug, used frequently for people with polycystic ovary syndrome. It is often prescribed over clomiphene because it has fewer side effects and a lower risk of multiple pregnancies. Clomid was once the first choice for treating infertility associated with PCOS, but studies show that letrozole may offer significantly higher rates of pregnancy.
The mechanism of action includes Ovulation Induction: Letrozole works by decreasing estrogen production in the body. Lower estrogen levels signal the pituitary gland to produce more follicle-stimulating hormone (FSH), which stimulates the ovaries to produce follicles and eggs. This can help induce ovulation in women who are not ovulating regularly or at all.
2. Short Half-Life: Compared to other ovulation-inducing agents like clomiphene citrate (Clomid), Letrozole has a shorter half-life, which means it leaves the body more quickly. This may reduce the risk of multiple pregnancies and other side effects.
3. Endometrial Receptivity: Some studies suggest that Letrozole may improve the endometrial lining, making it more receptive for embryo implantation, potentially increasing the chances of pregnancy.
Adverse effects and other considerations:
Common side effects may include hot flashes, headaches, and dizziness.
It is generally well-tolerated, but like all medications, it can have side effects.
There is some concern about the use of Letrozole in pregnancy, so it’s typically used under close medical supervision, and pregnancy is monitored closely. Its usually taken for a few days early in the menstrual cycle, typically from day 3 to day 7, to induce ovulation. The dosage and duration depend on the individual’s medical history and the physician’s judgment.
Ref :
https://www.parents.com/getting-pregnant/ovulation/ovulation-cycles-and-why-they-can-be-confusing 
