Average Female Reproductive Age Has Expanded, Study Finds

It looks like periods are coming earlier and menopause is starting later, according to a recent study published in the Journal of the American Medical Association (JAMA).

In this study, researchers surveyed 7,773 people about the ages they first menstruated and became naturally menopausal. Over the past 60 years, the average age of a first period decreased from 13.5 to 12.7 years and the average age of natural menopause increased by 1.5 years. In total, the mean reproductive life span has increased by 2.1 years. 

To determine the change, researchers compared participants' answers to a survey from the National Health and Nutrition Examination Survey conducted between 1959 and 1962.

A person’s lifestyle, environment, sociodemographic status, and behavior might also impact the length of a person’s reproductive age.

“While some factors like age, ethnicity, and genetics are nonmodifiable, there are several factors like diet, body weight, and smoking that can be modified,” says Dr. Sanaz Ghazal, MD, FACOG, cofounder of RISE Fertility. Study participants who are Black or Hispanic, smoked, or experience poverty were more likely to have a shorter reproductive life span.

Ghazal recommends people looking to optimize their fertility pay attention, when possible, to the factors they can control.  

External Factors Influence Fertility

One aspect that may be more difficult to change is a person’s socioeconomic status. “Higher socioeconomic demographics appear to equate with a longer reproductive time interval. Higher-income brackets equate to better options—nutrition, health care, less stress,” says Dr. Kecia Gaither, MD, MPH, FACOG, double board-certified in OB/GYN and Maternal Fetal Medicine, and director of perinatal services at NYC Health + Hospitals/Lincoln.

Gaither continues, “The takeaway message for younger women shouldn't be seen as a stressor—but a recognition of how external factors play into reproductive outcomes."

The study shows not only what people can do to expand their own reproductive age, but what societal changes could help.

Gaither adds, “If any segment of the population should take notice of the results, it’s those who can affect public health initiatives relating specifically to women’s health—with the knowledge that financial stability, nutrition, available health care, and decreased stress relate to optimal reproductive time intervals for women and ultimately optimal perinatal outcomes as a result.”

It’s Not Clear If The Age Fertility Peaks Has Changed

The study makes it clear that lifestyle factors can influence the length of reproductive age, but it does not demonstrate a link between this expansion and a later fertility peak.

“The survey-based study assessed the time of menopause, but it did not address if fertile time was extended in any capacity,” says Dr. Jennifer Hirshfeld-Cytron, MD, an OB/GYN and board-certified reproductive endocrinologist and the director of the center for fertility preservation at Fertility Centers of Illinois.

“While the study demonstrated a higher age of natural menopause, this does not mean that a woman’s reproductive function is any different. Simply because a woman is having her cycles longer doesn’t mean she is fertile longer," Hirshfeld-Cytron explains.

As of now, research shows people with ovaries still reach peak fertility in their 20s and it begins to decline in their early 30s. "Achieving a pregnancy becomes significantly more challenging over the age of 40 largely due to a decline in both egg quantity and quality,” says Ghazal.

About one in four people in their 20s to early 30s can get pregnant over one menstrual cycle. The same is true for only one in ten people around age 40.