Women of perimenopausal status or child-bearing potential: Femara should only be used in women with a clearly established postmenopausal status (see Precautions). As there are reports of women regaining ovarian function during treatment with Femara despite a clear postmenopausal status at start of therapy, the physician needs to discuss adequate contraception when necessary.
Pregnancy: Based on human experience in which there have been isolated cases of birth defects (labial fusion, ambiguous genitalia), Femara may cause congenital malformations when administered during pregnancy. Studies in animals have shown reproductive toxicity (see Pharmacology: Toxicology: Preclinical safety data under Actions).
Femara is contraindicated during pregnancy (see Contraindications and Pharmacology: Toxicology: Preclinical safety data under Actions).
Breast-feeding: It is unknown whether letrozole and its metabolites are excreted in human milk. A risk to the newborns/infants cannot be excluded.
Femara is contraindicated during breast-feeding (see Contraindications).
Fertility: The pharmacological action of letrozole is to reduce oestrogen production by aromatase inhibition. In premenopausal women, the inhibition of oestrogen synthesis leads to feedback increases in gonadotropin (LH, FSH) levels. Increased FSH levels in turn stimulate follicular growth, and can induce ovulation.