For Kristi and Carl Larson of Salt Lake, having triplets is triple the work and triple the joy.

The Larsons are the parents of Benjamin, Blake and Brooklynn, all 2 years old.

"They’re all busybodies," said their mother, "but they’re all very different. Blake is extremely outgoing, and he wants what he wants. Benjamin is very shy. Brooklynn is definitely a princess."

They all throw tantrums, too, she said, but fortunately not at the same time.

The three were born at Tripler Army Medical Center prematurely at 23 weeks, weighing between about 3 and 5 pounds. Having had two previous miscarriages, Kristi Larson was prescribed the fertility drug Clomid. The ovulation stimulant results in twins in about 7 percent of pregnancies in clinical trials and triplets in about 0.5 percent.

A report released this month by the Centers for Disease Control and Prevention noted a marked increase in multiple births over the past 30 years. The study found that nationally the twin birth rate rose 76 percent from 1980 through 2009, from roughly 19 to 33 twins born per 1,000 births.

That means 1 in every 30 babies born in the United States is a twin.

Hawaii was one of five states where the increase in twin birth rates rose by more than 100 percent.

The report cites the growing number of women who are delaying pregnancies until they are past 30, when multiple births are more likely, and increased use of fertility treatments as reasons for the rising rate of twin births.

Lana Fernandez, 36, of Waipio is expecting twins — a girl and a boy — in mid-April.

Her twins were conceived through in vitro fertilization, in which egg cells are fertilized with sperm outside the body in a laboratory. Once an embryo forms, it is transferred to the mother’s uterus. Fernandez’s firstborn, 2-year-old Leya, was also conceived through IVF.

Fernandez and her husband, Reynold, had been together for 17 years with no luck at having children before their daughter was born. They had gone through a battery of tests but were unable to find anything wrong. So they tried several different treatments, eventually opting for IVF.

"We got lucky," she said. "It happened the first time (cycle)."

Fernandez says she has a circle of friends who also have sought fertility treatment — one is expecting twin girls.

"It’s interesting how we’re all going through the same thing," she said. "A lot of us didn’t have any indications why we couldn’t get pregnant. Our families don’t have histories."

Dr. Carl Morton, co-director of the Pacific In-Vitro Fertilization Institute at Kapiolani Medical Center, says there are more women in their late 30s and early 40s coming to the clinic than in years past.

The clinic was the first of its kind in the state when it opened in 1985.

Today there are five such clinics on Oahu that report their birth outcome statistics to the Society for Assisted Reproductive Technology, a professional standards organization based in Birmingham, Ala.

Nationally about 33 percent of IVF patients under 35 had twins in 2009, according to the society. For women ages 35 to 37, the number was 27 percent, and for women ages 38 and 40, 21 percent.

For all age ranges, fewer than 2 percent had triplets.

Morton said there are guidelines on how many embryos to transfer, based on a woman’s age, but that each patient makes her own personal decision on the matter.

"There’s no way we can say for any woman who’s going through IVF, she’ll definitely have twins," said Morton. "It’s too much an individual response."

Hawaii is one of 15 states that mandate some insurance coverage for infertility treatments, which could be a contributing factor to the islands’ twin-baby boom. Hawaii law requires certain insurance plans to provide one cycle of IVF for patients with certain conditions. (The average U.S. cost for an IVF cycle is $12,400, according to the American Society of Reproductive Medicine.)

Helping moms with multiples cope and meet one another is part of the mission of Aloha Mothers of Multiples, a club on Oahu that started in 1967.

About 20 to 25 members show up at monthly meetings where a baby sitter is available, according to club co-president Lara Cody.

It’s a great way for mothers of twins, triplets or more to network, get professional advice and support, and swap clothes and baby equipment.

Lana Pinera-Pasquino, 32, of Hickam Air Force Base gave birth to identical twin girls Ava and Isabella, who will turn 3 in March, without the help of fertility treatments. She says one of the challenges of having multiples is to give each child enough individual attention.

"You have two kids that need the exact thing from you at the exact same time," she said. "They want to do everything together and everything the same. When we’re out, and when one says she has to go, the other says, ‘I have to pee-pee, too.’"

Getting both girls on the same feeding and napping schedule right out of the neonatal intensive care unit was helpful, she said. A sense of humor is also essential.

"It’s double, sometimes triple the work, but you get it all back," she said.

Only a mother of triplets can understand what another mother of triplets is going through, according to Larson. Through Aloha Mothers of Multiples she has met five other triplet families.

The equipment swaps have been a great help, especially since some gear, such as an in-line stroller for triplets, is available only by special order online.

Larson, 29, passes on her baby stuff to other triplet parents and gets advice from a mother of triplets who are a few years older than her children.

At first she had a color system for each infant to keep track of them and their bottles, but now has fun coordinating their outfits.

Sticking to a schedule is key to managing all three, she said.

"We’re a very schedule-oriented family," said Larson. "We can’t skip a nap or they get really grumpy and dad and I get grumpy."

The triplets have a special bond, she says, and even a language between themselves. One sibling will go to another, making a "doca-doca" sound, which Larson has interpreted to mean, "I’ll trade this toy for yours."

Benjamin, Blake and Brooklynn reached the milestones of teething, crawling and walking at the same time, although that doesn’t always happen with triplets, according to Larson.

When they visit Hono­lulu Zoo — an activity they love — the three hold hands and walk instead of ride in a stroller.

She chose to use cloth diapers as a more economical choice than going through disposables (at an average of six to eight diapers a day for each infant). She’s also decided it makes sense to potty-train them at different times, starting with Brooklynn first.

Both parents make an effort to go out with each child for one-on-one time.

Initially, there were nights without much sleep, but now the focus is on chasing after the toddlers busy exploring their world.

Looking back, Larson says she wouldn’t have done anything differently. What does she find the most rewarding?

"Just being their mom and watching them grow up," she said. "I get three times the kisses and hugs."