either lochia or estrogen withdrawal and not actual ovulation. Lactational amenorrhea has evolved as a mechanism for preserving the health of the mother. This period of infecundity allows the mother to focus her energy on breastfeeding as well as allow time for her body to heal between births. The frequency and durations of the feedings determine how long the mother will continue to be infecund during breastfeeding. However there is variation across different cultures. The Turkana, Gainj, and Quechua societies all breastfeed on demand until their child is around 2 years old. The timing of returned ovulation for these women is however varied. Because of this, interbirth intervals vary across these three societies. Return of fertility Return of menstruation following childbirth varies widely among individuals. This return does not necessarily mean a woman has begun to ovulate again. The first postpartum ovulatory cycle might occur before the first menses following childbirth or during subsequent cycles. A strong relationship has been observed between the amount of suckling and the contraceptive effect, such that the combination of feeding on demand rather than on a schedule and feeding only breast milk rather than supplementing the diet with other foods will greatly extend the period of effective contraception. In fact, it was found that among the Hutterites, more frequent bouts of nursing, in addition to maintenance of feeding in the night hours, led to longer lactational amenorrhea. An additional study that references this phenomenon cross-culturally was completed in the United Arab Emirates (UAE) and has similar findings. Mothers who breastfed exclusively longer showed a longer span of lactational amenorrhea, ranging from an average of 5.3 months in mothers who breastfed exclusively for only two months to an average of 9.6 months in mothers who did so for six months. Another factor shown to affect the length of amenorrhea was the mother's age. The older a woman was, the longer period of lactational amenorrhea she demonstrated. The same increase in length was found in multiparous women as opposed to primiparous. With regard to the use of breastfeeding as a form of contraception, most women who do not breastfeed will resume regular menstrual cycling within 1.5 to 2 months following parturition. Furthermore, the closer a woman's behavior is to the Seven Standards (see below) of ecological breastfeeding, the later (on average) her cycles will return. Overall, there are many factors including frequency of nursing, mother's age,