Although the twin birth rate rose by 76 percent between and , it declined 4 percent between and — the lowest rate in more than a decade. For women age 30 to 34, the twin birth rate declined by 10 percent; 12 percent for women age 35 to 39; and 23 percent for women age 40 and over. It's possible that the birth rate for twins has slowed down because fertility treatments have improved.
For example, with in vitro fertilizations IVF , doctors would usually transfer multiple embryos into the uterus at once to increase the chances of having one successful pregnancy. This also raises the likelihood of twins, but now doctors are transferring just one or, rarely, two embryos at a time to reduce high-risk pregnancies.
That's because women who have a multiple pregnancy carrying more than one baby are at a higher risk for complications, including preterm birth, low birth weight, preeclampsia high blood pressure , gestational diabetes, and a cesarean birth.
Although the birth rate for triplets and higher-order multiples had quadrupled between and , it declined by 6 percent in and was down 55 percent from the peak in The number of triplet and multiple births was 3,, which is the lowest number reported since It's also less than half of 7, — the highest number of triplet and higher-order multiple births ever reported in Similar to twin births, the slowdown in triplet and higher-order multiple births is likely due to the improvements in fertility treatments.
About 20 years ago, fertility specialists would transfer four embryos routinely for women of all ages, but now women are getting, on average, half as many embryos transferred at one time. BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals.
We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies. National Library of Medicine: Is the probability of having twins determined by genetics? National Vital Statistics Reports. Is twin childbearing on the decline?
For women under 35, infertility means not getting pregnant with timed intercourse in the course of a year. And for women over 35, this timeframe shortens to 6 months. They can tell you about any associated risks unique to you and if doing a multiple-embryo transfer with IVF might be an option. There are certainly both risks and rewards with twins. But before you get too carried away with dreaming, try first looking forward to seeing double… with the lines on your pregnancy test.
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Having twins naturally. The difficulty of getting pregnant and the percentage of miscarriages also increase as women get older. Family history — Twins tend to be more common in some families. There may be an underlying genetic factor that predisposes a woman to release more than one egg at a time, which increases the chance of having twins. Weight — There has been some consideration that women who are overweight are more likely to have more than one ovulation at a time, which may increase the chance of twins.
Diet — Interestingly, the highest rate of twins in the world is among a particular group in Africa called the Yoruba. One possible reason the twinning rate is so high among the Yoruba is that their diet is rich in a specific kind of yam that contains a phytoestrogen, or plant-like estrogen, that may increase the rate of twinning.
Race — Race may affect the rate of twins. All of these factors specifically affect the risk of conceiving fraternal twins.
Find care options. Wondering what the odds of conceiving twins are? Find out overall rates in the U. More About Multiples. Do Twins Really Run in Families? What Are the Different Types of Twins? View Sources. Oxford Academic, The risk of monozygotic twins after assisted reproductive technology: a systematic review and meta-analysis , February Two under Twin vs Twins.
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