According to Eurostat, women in Ireland, on average wait until they’re 30 to have babies.

But, according to Alan B. Copperman, medical director of Reproductive Medicine Associates of New York, women need to be mindful of their fertility in the years that precede the decision to have a baby. Copperman spoke to SELF magazine to discuss the most common factors attributing to infertility. According to the Centers for Disease Control and Prevention, the most common cause is polycystic ovary syndrome (PCOS). The Women's Health Clinic says PCOS is seen in 5-10 percent of women and is common to run in families. PCOS causes problems because polycystic ovaries are unable to produce the levels of hormones required to release one egg at ovulation each month. Typically, progesterone is not produced and a bleed does not occur. The cysts formed can also produce excessive amounts of male hormone. Another common factor of infertility is endometriosis. According to the Endometriosis Association of Ireland, It is estimated that between two and ten percent of the women within the general population have endometriosis and that up to 50 percent of the infertile women have endometriosis. Women with endometriosis often have severe complaints and significantly reduced quality of life, including restraint of normal activities, pain/discomfort, and anxiety/depression. The next most common cause of infertility, terrifyingly, is STI’s and other infections. These can cause a blockage in the fallopian tubes. “Tubal infection is most likely caused by an organism that starts in the cervix and then goes up into fallopian tubes,” explains fertility expert, Meike L. Uhler, M.D. Gonorrhea and chlamydia are the most common cause of this. “If left untreated, [an infection] can cause scarring of the fallopian tubes. That’s where the egg and sperm meet, and they’re not able to if it’s blocked,” she said. Furthermore, untreated STI’s can cause pelvic inflammatory disease (PID), a condition that leads to an infection of reproductive organs, usually the uterus or fallopian tubes. Other causes of infertility include excess body weight and age. For women who fear they might suffer from any of the above conditions, it is recommended that you visit a doctor regularly and always, always practice safe sex.