Contrary to popular perception that infertility rates are on the rise, the percentage of women unable to conceive after at least one year of unprotected sex has fallen in the last three decades, according to data from the Centers for Disease Control and Prevention (CDC).

The data may not be entirely optimistic, as researchers behind the report argue women are deciding to have children later in life and therefore face greater risk for pregnancy complications. Between 1982 and 2010, the rates for infertility among married women ages 15-44 dropped from 8.5 percent to six percent. That equates to roughly one million fewer cases over the 28-year period.

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The study included three classifications of “infertility status,” including surgically sterile, infertile, or presumed fertile. Women who didn’t identify as either surgically sterile or infertile fell into the category of presumed fertile, which acts as a residual category, the report notes.

Among the oldest band of women, ages 35-44, infertility rates saw a sharp decline. Rates dropped from 44 percent in 1982 to 27 percent between 2006 and 2010.

But as these rates declined, the rates of impaired fecundity — not being able to carry a pregnancy to term — rose marginally during the three decades, from 10.8 percent in 1982 to 12.1 percent in 2010. Impaired fecundity peaked in 2002 at 15 percent.

Lead researcher Anjani Chandra, a demographer at the CDC's National Center for Health Statistics, attributed this increase to the trend of delayed pregnancy among women. Rather than conceive their first child in their mid- to late-20s, women have started conceiving in their early 30s. This puts them slightly behind their years of peak fertility, which increases the chances of fetal abnormalities and pregnancy complications.

“Chromosomes are more likely to stick together and do not separate as easily at a later age," Dr. Saad Ghazal Al Aswad told The National. Al Aswad's work as a senior consultant in the Department of Obstetrics and Gynecology at Tawam Hospital showed increased risk for diabetes among delayed pregnancies in the United Arab Emirates.

"This is particularly true here in the UAE,” he said of chromosomal problems, “where there are many consanguineous marriages, and therefore genetic similarities, between couples."

Women between the ages of 15 and 24 saw 11 percent of pregnancies result in impaired fecundity in recent years. This is contrasted to 47 percent between the ages of 40 and 44, according to the CDC’s report.

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One critical caveat in the study, however, is that not all infertile, childless women are seeking pregnancy. Some 40 percent of women who were infertile had no intention of bearing children — meaning their infertility did not meaningfully impact their lives in the same way as it did for other women.

“There is value in determining the population-based prevalence of fertility problems independent of fertility intentions, with the recognition that there are a wide range of responses to infertility that may not involve medical services," the researchers concluded.

It’s for this reason, they noted, that infertility must be examined comprehensively and consistently, as influential factors change just as often.

“Fertility intentions may change over the course of time in response, for example, to changes in relationship status, socioeconomic status, and availability of infertility services,” states the report, “further highlighting the role of population-based, consistently measured indicators such as impaired fecundity and 12-month infertility.”