As per a new 2014 report released by the US Centers for Disease Control and Prevention (CDC), twinning rate has hit all time high in the United States in 2014. In 2014, the birth rate for twins was 33.9 sets of twins per 1,000 births compared to 33.7 in 2013. It has been reported that mothers continued to get older in 2014 with the average age for the first-time mother has now become 26.3, which it was 26 in 2013. According to a report from the National Center for Health Statistics, out of all the twins recorded 78,788 were born to white women, 23,546 were born to black women and 22,051 were born to Latinas.
In 2104, about 135,336 twins were born in the U.S, which was 2% higher compared to it was in 2013, but nearly 3% lower than the all-time high of 138,961 twin births, set in 2007. The reason for so much increase in twin birth rates might be due to the fact that American women are waiting longer to get pregnant. It might be the fact that aged women tend to produce higher quantities of hormone that triggers the maturation of an egg-producing follicle. It further means a woman is more likely to have two eggs available for fertilization during a single cycle in her 30s than she is during her 20s. Though, it is not always that women in later age will have fraternal twins as older eggs are more likely to be unviable, a significant portion of them can be expected to have fraternal twins.
Another reason for the increase in twin birth rate could be the success of In-Vitro fertilization. The Society for Assisted Reproduction Technology advises many patients with a good prognosis for a successful pregnancy to transfer no more than two embryos at a time. Since 1980s, about 79% increase in twin birth rates have been reported till now with the birth rate for triplets and higher-order multiples has declined 41% since peaking in 1998. In 2014, 113.5 out of every 100,000 births involved higher-order multiples, the lowest it has been in 20 years.