How doe implanon work exactly? does it destroy the fetus if u become pregnant? or does it simply prevent the egg and sperm from uniting? is it safe

Implanon/Nexplanon: Progestin implants that slowly releases drug over 3 years. Progesterone suppresses ovulation, thickens cervical mucus & thins endometrial lining of uterus. May still ovulate. Works by preventing sperm passing into uterus & by not allowing a 'hospitable' endometrium in which a fertilized egg could implant. Effective (assures compliance). Spotting most common ae; ha, acne, wt gain, breast tndr.