Are Twin Pregnancies on the Rise?Dianna Graveman | 5, February 2012
No, you're not seeing double. Twins are on the rise! You're likely to encounter a pair everywhere you go: the shopping mall, your pediatrician's office, the park. Are there really more twins these days, or does it just seem so?
The National Center for Health Statistics (NCHS) Data Brief No. 80 (Centers for Disease Control and Prevention, 2012) reported that the incidence of multiple births began to rise in the early 1980s. Until then, the occurrence of multiples had remained pretty steady (at about 2% of all births) since 1915, the first year for which there is reliable data. In 2009, one in every thirty children born in the United States was a twin, compared to one in 53 babies born in 1980. In fact, according to the NCHS brief, the number of twin births doubled from 1980 to 2009, and the rate of twin births rose by 76% during those years. Twin births, in this report, refers to "an individual live birth in a twin pregnancy," and does not include triplets or other multiple births. The rate of twin births refers to "the number of twin births per 1,000 total births."
Some of this increase can be attributed to the fact that many women are waiting well into their thirties to have children. A higher percentage of women attend college than ever before, and more opportunities exist for career advancement. But with waiting comes other considerations: A woman who gives birth at age 35 has a four times greater chance of having twins than a mother who is twenty. Some studies have shown that a woman in her thirties may produce more follicle-stimulating hormone (FSH), which can increase the likelihood that she will also produce more than one egg each cycle. The increase in maternal age, according to the NCHS report, accounts for about one-third of the increase in twin births over the past three decades.
A rise in the use of fertility treatments during the 1980s and 1990s, including both ovulation stimulation medicines and assisted reproductive methods like in vitro fertilization (IVF), has also led to an increase in multiple births. These methods and treatments tend to be more common among older mothers who have exhausted other efforts to conceive and/or who may be in a financially more stable situation than a younger woman and better able to afford the interventions. The highest increase in twin births occurred among mothers forty and older, partly due to the use of fertility treatments; however, studies have also shown women over 40 are more likely than younger women to request that two or more embryos be implanted during IVF.
According to NCHS, fertility treatments account for the remaining two-thirds of the increase in twin births not attributed to an increase in maternal age.
Studies have found similar trends associated with maternal age and infertility therapies in other countries. However, rates of increase vary from state to state within the U.S., and even among women of different races. For example, the likelihood of twins doubled from 1980 to 2009 for white women, rose by about one-half for black women, and rose by one-third for Hispanic women.
While the Centers for Disease Control and Prevention (CDC) does report that a higher incidence of multiple births can lead to health complications and increased medical costs, most parents consider a twin pregnancy (or an even greater multiple) to be a blessing. If you find you are among those lucky parents who will soon welcome two little bundles of joy, relax, consult your healthcare provider about medical concerns, and talk with other parents of multiples for support. Most of all, have fun! Life is about to bring you double the excitement and twice the love you had hoped for.
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