Twin birth rates have reached an unprecedented high in the United States, the Centers for Disease Control and Prevention have recently revealed on Wednesday, December 23.
According to officials from the National Center for Health Statistics, never before has the nation experienced such a boom in twin births. More precisely, in 2014 there were 33.9 twins for every 1,000 births, whereas back in 1980 the prevalence of such deliveries was almost twice as low, at around 18.9 per 1,000.
The number of twin births has increased steadily in recent years, the current value being slightly higher even when compared to the 2013 figure, when around 33.7 twins were reported for every 1,000 births.
On the other hand, the number of triplet deliveries has suffered a downturn lately, and a similar decline was also identified when it came to births involving a larger number of infants.
Namely, in 2014 there were around 113.5 such deliveries per 100,000, a significant drop since 2013 when 119.5 such births occurred for every 100,000 births.
The percentage of triplet and higher-order deliveries has dwindled by around 40% when contrasted against its maximum value, which was reached in 1998, when there were 193.5 such births per 100,000.
In fact, it appears last year’s estimates have marked a record low, the number of multiple births involving at least three babies being the smallest in the last 2 decades.
According to health officials, there may be various explanations for these recently identified trends, consisting in a growing number of twins, coupled with a tapering number of triplets and other multiple births.
For example, women are now conceiving babies at later stages than before: their mature age elevates the chances that ovarian follicles will release two eggs instead of one, which makes the possibility of giving birth to twins much higher.
Specifically, the mean age of first time mothers has been rising in recent years, having reached 26.3 years in 2014, a slight increase even since 2013, when it was estimated at approximately 26 years.
Overall, the percentage of expectant mothers in their early 20s has waned, hitting rock bottom in 2014. Also, probably due to increased awareness and broader use of condoms and other contraceptives, teen pregnancy rates have been declining by 9%, from 26.5 per 1,000, as reported in 2013, to approximately 24.2 per 1,000 in 2014.
Meanwhile, the proportion of deliveries involving women in their late 20s or even 30s and 40s has been soaring.
Moreover, a growing number of female patients wishing to conceive have been resorting to fertility clinics, assisted reproductive technologies such as in vitro fertilization (IVF) significantly elevating the likelihood of a multiple birth.
For instance, in 2013 it was determined that around 77% of the deliveries of triplets, quadrupeds etc. and 36% of the total number of twin births could be attributed to various fertility treatments.
On the other hand, given the fact IVF has become more effective, and multi-fetal pregnancies tend to be more hazardous, having been associated with a higher risk of miscarriage, premature birth and neonatal death, medical practitioners have been reducing the number of embryos to be transferred, limiting it at three or less.
As researchers point out, all these recent happenings could account for the sharp fall identified when it comes to deliveries with triplets or higher order multiples.
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