“Four out of 10 kids that I saw today at a kids cafe were twins, and they were all fraternal,” wrote an anonymous mom in a post on an online community that has 2.6 million moms and wannabe moms as members.

Another mom replied to the post, saying, “It’s because more women are having babies through in vitro fertilization these days. I envy those mothers who got two birds with one stone.”

Such dialogue is common nowadays in South Korea, which faces a decreasing economically productive population.

Indeed, the number of newly born multiple-birth babies in Korea neared 30,000 in 2016, accounting for 6.6 percent of total newborns, which marked 406,000 in the same year, showed provisional data from Statistics Korea.

The number of newborns has remained below 500,000 for the past 10 years, which has resulted in a birthrate of less than 1.2 births per woman. Last year, the rate stood at 1.17.

The decline in the birthrate can be attributed to an increased number of Korean female workers opting to extend their education and careers, defying the traditional perception of middle-aged women becoming full-time housekeepers and mothers.

The average age for women to wed stood at 30.11 in 2016, up 0.15 year from 2015, while the age of giving birth to the first baby reached 31.4, up 0.2 year.

As a result, an increasing number of women are having difficulties in getting pregnant due to physical challenges as they attempt to conceive at older ages. The number of couples opting for artificial insemination has accordingly increased.

The phenomenon has become mainstream and created “twin fever” in the media.

The fever officially began in 2013 with the TV series “The Return of Superman,” featuring toddlers and their celebrity fathers.

Korean comedian Lee Hwi-jae and his fraternal twin boys Seo-eon and Seo-joon introduced what raising a pair of male twins would look like and created a favorable image of multiple births.

The popularity of twins peaked with the debut of the triplet sons of actor Song Il-gook on the same show the following year.

Both Lee and Song made public that they had the children through IVF. Lee was married to a florist, and Song to a judge, meaning both are working moms, who are also in their mid-30s.

The probability of conceiving multiples increases for women utilizing assisted reproductive technologies, or ART, including IVF treatment.

“The ART treatments include ovulation inductions, in which multiple eggs are fertilized to be implanted, so the probability is high,” said Dr. Ahn Byul-nim, an obstetrics and gynecology specialist at a hospital in Seoul.

Despite the possible side effects and difficulties of raising two kids at a time, there are some who are misled by the popular twin stories.

“I am a healthy woman who had a normal pregnancy and labor process for the first baby, but I want to have a second (pregnancy) with twins,” said a mother nicknamed “newlywed bride.” “Does anyone know a hospital that allows prescription of injections for super ovulation or follicle?”

Artificially inducing super ovulation can cause complications, such as ovarian hyper stimulation syndrome, Ahn said.

“I believe natural conception is the best. There are many who have no choice but to receive the medical treatments for pregnancy,” Ahn said. “I would say it is not desirable to see some who voluntarily choose the treatments only to have twins.”

Seo Jeong-eun, 32, still vividly remembers the torturous pain in her breasts when she fed her identical twin sons in either arm six years ago.

“Holding the twins both at one time to feed both feels not only painful but also humiliating as a woman,” she said. “Otherwise, you have to breast-feed one at a time, which seems to never end.”

Seo gave birth to identical twins when she was 26, far younger than today’s average marriage age in Korea.

She said she had the twins partly thanks to her youth, but acknowledged that it was also part of genetic factors in her family.

Seo’s older sister is currently a mother of two sets of twins -- the elder twins are fraternal, while the younger ones are identical.

According to the American Society for Reproductive Medicine, the chances of having twins is higher especially for women who have fraternal twins in their family tree. Women who are fraternal twins themselves have a 1 in 60 chance of having their own twins, a report by the organization said. Men who are fraternal twins have a 1 in 125 chance of fathering twins.

“My mom is a fraternal twin,” Seo said. “We must have inherited the twin gene, I guess.”

It is hard to gauge the chances of having identical and fraternal twins when genetics are factored in, but experts say the chances of having fraternal pairs get higher with medical treatments because more than one fertilized egg is used.

“One of the chief reasons we see more fraternal twins or triplets is that more and more women undergo IVF procedures for pregnancy difficulties,” Ahn said.

Aside from medical assistance, natural conception of fraternal twins or multiples is often possible in women in their late 30s and above, due to irregular ovulation periods and number of eggs, according to medical experts.

The twin fever reflects a notable change in people’s perception about having kids and about twins, said Lee Taek-gwang, a cultural professor at Kyung Hee University.

“Our society had a negative perception about twins in the past, especially in a patriarchal culture in which hierarchy of male offspring was crucial,” Lee said.

In conservative and patriarchal families, seniority used to be the utmost value, according to the professor, which was feared to be shaken by simultaneous births of multiple babies.

“The TV show helped remove such old prejudices and even changed the minds of people who shunned having babies due to socioeconomic problems by giving them a new idea of having two kids at a time.”

To those trying to have twins, Seo warns, “Don’t dare to think that it will just take doubled efforts to raise multiple kids of the same age at once. It feels 10 times harder in reality (when factoring in the unexpected variables or emergencies).”

Another awful moment Seo recalled was when she had to rush to the hospital, carrying one on her back and the other in front.

“I don’t think celebs who have twins or triplets went through all the difficulties I had, as they would get a lot of support from nannies,” she said. “What we see on the TV screen is mostly the fun parts of having multiple children, which may spur general viewers to overlook the real difficulties.”

By Song Su-hyun (song@heraldcorp.com)