Reproduction - Infertility And Its Unexpected Multiplier Effect

Women in their early 30s bear most of the triplets, quadruplets, and higher order multiples born in the United States. Women in their late 40s and early 50s, however, have by far the highest rate of multiple births per delivery.

In the previous panel we saw that more women are choosing to have children later in life. One of the side effects of this trend is that more couples are having difficulty conceiving and are turning to fertility treatments in greater numbers. The rising numbers of high order multiple deliveries (triplets and higher order multiples) tells us that the treatments for infertility that became available throughout the 1970s are definitely being used.

According to the National Center for Health Statistics, an estimated 80% of triplet and higher order multiples are the result of the use of assisted reproductive technologies⁵(ART) and ovulation-inducing drugs. There is a naturally higher likelihood of multiple births with increasing maternal age. However, that (natural) increase is slight and the increase we are seeing in the United States over the last decades is dramatic.

The graph shows the distribution of all higher order multiple deliveries in the year 2000 by age of mother. The rate is the number of multiple deliveries per 100,000 live births. The total number of multiple births (including twins) is shown in the form of a solid line that peaks in the 30 to 34 year age group. The rates for women over 30 years of age are all higher than the average and for the oldest moms it reaches a remarkable 1,998 high order multiples per 100,000 live births.

The rates for 2000 reflect a striking rise in multiple deliveries since the 1970s⁶. There was very little change in the rate of triplet and higher order multiple births during the period 1930 through 1970. The rate remained stable at approximately 30 per 100,000 live births. The dramatic rise in this rate to 180 in 2000 illustrates the impact of ART and other infertility treatments.

Rate of Multiples 1980 and 2000

The chart to the left shows the rates of high order multiples for the years 1980 and 2000 by maternal age group.

The postponing of childbearing clearly has an impact on the ease with which older parents enter the parenting game. Headlines about 40 something actresses giving birth creates the false impression for many women that postponing child- bearing until their late 30s or even 40s is a reasonable option. What the headlines do not mention is the fact that women in their 40s having babies are usually doing so with donor eggs, according to Dr. David Adamson, a leading fertility specialist at Stanford University. This explains to a large degree why the rate of multiples for women over 45 shoots up dramatically from already high rates for all women over 35.

Turning back the biological clock has limits, many of which were only fully recognized in the 1990s according to Dr. Sarah Berga, a reproductive endocrinologist at the University of Pittsburgh. We may assume that unless and until new fertility treatments are found, we will not see a continued trend towards ever-greater postponement of child- bearing. And for those who have postponed a bit too long, beware what you wish for — quadruples are a handful.

Source: Center for Disease Control, National Vital Statistics Report, "Births: Final Data for 2000," page 87 and Morbidity and Mortality Weekly Report, "Contribution of Assisted Reproductive Technology and Ovulation-Inducing Drugs to Triplet and Higher-Order Multiple Births: United States, 1980-1997." Statements by Doctors Adamson and Berga are from an article by Nancy Gibbs, "Making Time for a Baby", Time, April 15, 2002, pages 48-54.