Suzanne Severy Comeau and her sister, Jennifer, as 12-year-old twins entwined in the same bed after the death of their grandfather, awoke simultaneously with the same nightmare.
In college, the phone would ring and one would know it was the other on the line. Even today, the twins end up buying the same birthday card for each other 75 percent of the time.
"There was a special bond between us, and we felt unique," said Comeau, now 37 and a teacher, who grew up in the 1970s when multiple births were oddities.
But today, with more women postponing marriage and resorting to fertility treatments, twins are a fact of modern life. Between 1980 and 2002, the incidence of twins jumped 65 percent, according to statistics from the Centers for Disease Control and Prevention.
When Comeau goes back to her kindergarten in Carlisle, Mass., this fall, 15 of the 70 children -- or 20 percent of the entire class -- will be either a twin or a triplet.
"We've been aware of the increase in twins for a while because it's a small community, and we know who are families are," said Patrice Hurley, principal at the public school in Carlisle, an affluent town of 5,500. "It's really an exciting situation."
The National Center for Health Statistics reports that 136,328 — or about 3 percent of the babies born in the United States in 2002 — were multiples. Of those, 128,665 were twins, 7,110 triplets, 468 quintuplets and 85 higher-order births.
In the three decades since Comeau and her twin were born, the average age of mothers for all births rose from 24.6 years to 27.2 years. The largest increase is for women in their 30s and 40s, with a jump in birthrate from 2 percent to 9.1 percent.
The trend in delayed childbirth is "universally observed" nationwide and among all groups in the population, according to the CDC's Web site.
Comeau, who has taught for nine years, has also observed that her students' parents are "a little older than the norm."
"It's not a surprise to have so many twins in the class," joked Comeau. "People say there's something interesting in the water in Carlisle."
Teachers like Comeau work hard to get to know twins individually and not to mix them up, but mistakes happen.
"We are only human, after all," she said. "But we try to let them be who they are and celebrate all the things that make them different."
Twins can occur in two ways. In the case of identical -- or monozygous -- twins, a single fertilized egg splits, creating two embryos of the same sex with the same DNA.
With fraternal — or dizygous — twins, the woman releases two eggs, which are fertilized by two different sperm. The twins are genetically like ordinary siblings, only born at the same time, and can be different sexes.
Identical twins are a random occurence, although anecdotally families say they can skip generations. Comeau's paternal grandmother had stillborn twin boys. The rate among identical twins has remained relatively unchanged.
But fraternal twins are on the rise. Some of the increase can be attributed to a woman's age, but more often fertility treatment is the cause, says Dr. F. Sessions Cole, director of newborn medicine at St. Louis Children's Hospital in St. Louis.
Hormone treatments stimulate the ovaries to produce more than one egg; and in in vitro fertilization, doctors harvest, fertilize and reimplant multiple eggs to increase a woman's chance of conception. The more eggs, the better the odds.
Mary Beth Stevenson gave birth to triplets — a set of identical girls and a boy — who last spring completed kindergarten where Comeau attended decades earlier. At 34, she turned to IVF and conceived after six tries.
"You know there's an increased risk, but you may never have children on your own," said Stevenson, who had been pregnant before and had a miscarriage. "I just wanted one healthy child."
On the day of her ultrasound, Stevenson feared there would be no heartbeat, but when the doctor heard the second and third beats she thought, "First they tell me I won't have children, and now I have three children."
Their life was a whirlwind of breast-feeding for three, triple cases of formula and — at year's end — a total of 6,600 diapers. Friends showered them with gifts, and every relative and neighbor fought to feed or cuddle the babies.
Today Stevenson, at 41, runs a window treatment business at home and encourages her triplets' independence.
In Massachusetts, as in many other states, parents are legally allowed to make the decision about whether twins are separated or kept together in school.
Her triplets chose to have separate teachers so they could have "their own birthday parties and friends," said Stevenson. "One of my daughters had a set of twins in her class and said, 'Mommy, they don't know how to separate.' My kids went into the classroom the first day and never looked back."
But, said Cole, not all multiple birth stories have a rosy ending. As the number of babies in the womb rises, so does the risk of premature birth -- a danger to both mother and her babies.
Any birth before 37 weeks gestation — three weeks before the due date — is considered premature. And even as advances in neonatology help many survive, they are at greater risk for cerebral palsy, hearing problems, lung and heart complications and learning disabilities, according to Cole.
In the recent Arizona case of the Masche sextuplets — all of whom survived — their mother suffered heart failure during the arduous birth.
In some cases, women and their doctors must make the painful decision to abort one or more of the growing fetuses in a multiple pregnancy for the viability of the others.
"Parents struggle with these decisions," said Cole. "It's very important to find those boundaries and not go fishing around in the middle of a pregnancy for impossible answers."
Still, many multiple births go smoothly, and parenting multiples can be both a "big blessing and very challenging," said Pamela Fierro, author of "Everything Twins, Triplets and More," who also writes on the topic for About.com.
Fierro raised twin girls, now 12, who are "very competitive but deeply connected."
"Babies can really put a strain on a marriage, finances and other siblings in a house," she said. "Babies are everything in your life and very consuming."
She urges parents to respect each child as an individual and avoid comparisons. Mothers need to ask for help and keep a sense of perspective.
Teachers, too, need to revere the special bonds that make multiples emotionally inseparable. Comeau needs only to look to her own twin.
"We have the most unique relationship in the world," said Comeau's twin, Jennifer Ward of Melrose, Mass. "I love my husband, but everything is better with her company. We will be together in our high heels and our rockers."