The rate keeps rising for (naturally) two big reasons. More twins are being born now than ever before. Parents are increasingly using in-vitro fertilization and deciding to have children later in life. The twin rate could continue to go up as more nations push these factors higher.
It has been widely assumed that there has been an increase in twins over the years, largely attributed to fertility treatments. But the increase in the multiple birth rate means not just more twins, but also higher order multiples, such as triplets, quadruplets and the like.
Birth of twins has significantly increased over the past years, as you can see on the graph below. As of 2003, there are on average around 16 sets of twins born per 1,000 births in the United States. It is estimated that 1 in 250 natural pregnancies will naturally result in twins.
The chances of having identical twins is relatively rare. For every 1,000 births, identical twins happen every 3rd or 4th. Although, the use of fertility treatments will increase the risk of having identical twins. Identical twins actually make up 0.95% of pregnancies that were conceived with treatment.
People over 30, and particularly those over age 35, are more likely to conceive twins. 4 This is because the level of follicle-stimulating hormone (FSH) rises as birthing parents get older. FSH is responsible for the development of eggs in the ovaries before they are released.
The older the parent, the more likely they are to have naturally occurring multiple births, according to research from Brown University. That's because older childbearing people have higher levels of follicle stimulation hormones (FSH), making it more likely to have multiple eggs released instead of just one.
In Australia, twins happen in 1 in every 80 births. This means that 1 in 40 Australians is a twin.
Everyone has the same chance of having identical twins: about 1 in 250. Identical twins do not run in families. But there are some factors that make having non-identical twins more likely: non-identical twins are more common in some ethnic groups, with the highest rate among Nigerians and the lowest among Japanese.
You've probably heard of identical and fraternal twins, but a report released this week says there's a third kind -- sesquizygous twins or "semi-identical." Researchers say they share anywhere from 50 to 100% of their genomes.
The quick answer to this question is that, in a twin pregnancy, it is the mother's genes that determine twins. First up, giving birth to identical twins is not genetic, but conceiving fraternal twins is. The mother may have the genetic trait of releasing two eggs in one menstrual cycle.
About 1 in 3 of all sets of twin births are vaginal births. You may choose to have an elective caesarean, or your doctor may recommend a caesarean section because of potential complications. Even if you plan a vaginal birth, you may end up having an emergency caesarean section due to complications during labour.
Fraternal twins tend to live longer than singletons. But identical twins generally outlive fraternal ones.
Are twins hereditary? Yes, some types of twins are hereditary, meaning that twins run in families. Heredity on the mother's side ups a couple's odds of conceiving fraternal twins. Fraternal twins are two babies from two different eggs that were released from the ovaries simultaneously.
There is no proven scientific explanation for the high rate of twins in Igbo-Ora, a city of at least 200,000 people 135 kilometers (83 miles) south of Nigeria's largest city, Lagos. But many in Igbo-Ora believe it can be traced to women's diets.
Asian Americans and Native Americans have the lowest rates for twins. White people assigned female at birth have the highest rate of higher-order multiple births (triplets or more). This is especially true for those older than 35.
Vietnam was the country with the fewest twins (6.2 per 1,000 births) and Benin was the country with the most (27.9 per 1,000). Over time, some of these developing countries saw increases in twins, but some saw decreases and some stayed the same, with any changes tending to be small.
In 1997, the McCaughey septuplets, born in Des Moines, Iowa, became the first septuplets known to survive infancy. Multiple births of as many as eight babies have been born alive, the first surviving set on record goes to the Suleman octuplets, born in 2009 in Bellflower, California.
Australians Anna and Lucy DeCinque call themselves the “most identical twins in the world”, and work to live up to their self-proclaimed title. They're engaged to the same man, have the same bathroom schedule, and work the same job – one for a salary the other as a volunteer, for legal reasons.
A set of nonuplets was born on 13 June 1971, in Sydney, Australia to Geraldine Brodrick and her husband Leonard. They were five boys and four girls; two of the boys were stillborn and the last of the surviving babies, a boy named Richard, died six days after the birth.
They come from the same fertilized egg and share the same genetic blueprint. To a standard DNA test, they are indistinguishable. But any forensics expert will tell you that there is at least one surefire way to tell them apart: identical twins do not have matching fingerprints.
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That's not all, Monga says. Women pregnant with twins complain of more back pain, sleeping difficulties, and heartburn than those who are carrying one child. Being pregnant with twins also carries a higher rate of maternal anemia and a higher rate of postpartum hemorrhage (bleeding) after delivery.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.