It can seem like infertility is on the rise, especially in developed countries as women wait longer to start families. But according to a new analysis of 277 surveys, conducted by researchers at the World Health Organization and other institutions, infertility trends around the world stayed largely the same from 1990 to 2010.
Worldwide in 2010, 1.9% of women ages 20 to 44 who wanted to have babies were unable to give birth to a first child, wrote Gretchen Stevens of the World Health Organization and coauthors in a study in the journal PLOS Medicine. Among women who had already given birth, 10.5% were unable to have another child, the group reported.
Those numbers were only slightly changed from 20 years earlier, when so-called primary infertility (inability to have a first child) was 2.0% worldwide and secondary infertility (inability to have a subsequent child) was 10.2%.
"Independent from population growth and worldwide declines in the preferred number of children, we found little evidence of changes in infertility over two decades," the authors wrote.
The two exceptions were sub-Saharan Africa and South Asia, where infertility declined significantly. Stevens and her collaborators suggested that may be linked to reductions in rates of sexually transmitted diseases such as gonorrhea and chlamydia, which can cause infertility when left untreated.
Central and Eastern Europe and Central Asia, on the other hand, had relatively high rates of secondary infertility, which the coauthors suggested might be associated with the region's higher incidence of abortion and the persistence of unsafe abortion practices that can cause complications that affect fertility.
Estimating infertility is tricky, the team wrote, because few researchers have attempted to do comparative analysis of different countries' health survey data in the past, and no one has applied a consistent method to all the sources of data. This group collected data from demographic and reproductive health surveys that had collected women's ages, whether women were part of a couple, whether they were using contraception, time since first and last births, time since first union and desire to have a child. U.S. data came from the National Survey of Family and Growth, conducted by the U.S. Centers for Disease Control and Prevention.
In all, they said, 48.5 million couples around the world are unable to have a child, up 6.5 million from 1990. They attributed the rise in absolute numbers to population growth.