Infertility is defined as the inability to conceive or carry a pregnancy to live birth after one year of regular unprotected sex. There are various medical and demographic definitions of infertility, with medical definitions focusing on the inability to conceive and demographic definitions including the inability to carry a pregnancy to term. Infertility can be primary or secondary, with primary infertility referring to those who have never conceived and secondary referring to those who have previously conceived. Infertility is estimated to affect around 15% of reproductive aged couples globally based on WHO data, though estimates vary significantly between studies and regions.