For Luke Foreman, seeing double has always been the norm.
Growing up alongside twin Megan, the California-born 16-year-old has never thought twice about the frequency of twins around him. But, late last year, Luke was surprised to learn his school could tie the world record for the most twins in the same academic year at one school.
A dramatic rise in multiple-child pregnancies has left many schools with record-smashing numbers of twins and triplets. Luke Foreman's Staples High School in Westport, Connecticut, tied the Guinness World Record this year for most sets of twins in a grade at 16.
The high school shares the title with Valley Southwoods Freshman High School in West Des Moines, Iowa.
The schools, however, may not hold the record for long. Connecticut's Greenwich High School hopes to beat the world record with 18 pair of twins in its class of 2016.
"I was kind of stunned," Nancy Lanzoni, mother of twins Ben and Willy, said when she learned the Greenwich High School boasts a total 62 sets of twins in four grades.
The surprising numbers reflect a rise in multiple births in the United States.
"There's no question that the number and rate of multiple births has increased substantially in recent years," Joyce Martin, an epidemiologist at the National Center for Health Statistics (NCHS), explains.
In a report published earlier this year, the NCHS found there has been a 76% increase in the incidence of twins from 1980 to 2009. One in every 30 babies born in the United States in 2009 was a twin, compared to 1 in every 53 babies born in 1980.
"The increase of triplets and higher was almost 400%," Martin says. "You don't typically see that kind of change occurring naturally."
The remarkable increase is largely attributed to the increasingly older age of mothers and the increased use of infertility treatments, which gained popularity in the 1980s and 1990s.
"A lot of it is driven by demographics," Martin explains. "Moms tend to be older. When older women give birth naturally, they are more likely to have twins spontaneously and are more likely to have treatments."
It comes as little surprise that two Connecticut high schools have competed for the top twin-related prize. Connecticut saw the highest twin birth rate in 2009 with nearly 5% of all births in the state being twins. Massachusetts, New Jersey, New Hampshire and Rhode Island were not far behind.
"I've noticed there are more twins and triplets," John Dodig, principal of Staples High School, says. "I'm sure (our record) will be very short lived in the Guinness World Record history."