While the hospital has delivered more than 5,500 babies in the past year, the latest span of multiple births was definitely out of the ordinary.

"It's rare for us to have this many sets of multiples at the same time," said Justin Paquette, a hospital spokesman. "It seems like we're always busy now."

The rest of July and August also are expected to be busy on the birthing front, hospital officials said.

Last week was pretty hectic too, with 14 babies being delivered in a three-hour period.

In the past 20 years, multiple births have increased nearly 70 percent nationwide, according to the March of Dimes. Now, more than 3 percent of babies born in the country comes in sets of two, three or more, with 94 percent of the multiples being twins.

The increase in multiple births nationally is partially attributed to women waiting longer to become mothers and requiring the use of fertility drugs, said Dr. Joseph Morris, lead OBGYN hospitalist at AAMC.

Of the hospital's recent span of multiple births, four sets of the twins were the result of spontaneous fertility - or without the assistance of drugs - two were done through invitro fertilization; and the triplets were conceived through intrauterine insemination, hospital officials said. Intrauterine insemination is performed by using a catheter to insert sperm into the uterus.

"Sociologically, being pregnant as a teenager is not the best time to get pregnant, but biologically it is. The longer you wait into your 30s and 40s, (the chances of conceiving are lower)." Dr. Morris said. "You can get assistance, and most of the time, you end up with multiples."

Women have higher than average chances of conceiving twins if they have a personal or family history of fraternal twins, or if they are obese or tall. Black women are more likely than white women to have twins, while Asian women are least likely to have multiple births, according to the American Society for Reproductive Medicine.

The families

Last winter, Natalie Cronin's pregnancy began to feel familiar.

It was unlike the pregnancy she had with her toddler son, Tadhg. She felt full and heavy, which was how she felt when she carried twins years before, but those babies didn't survive.

So shortly before Christmas, she told her husband, Tim, that she was having twins. Her doctor later confirmed it.

On Monday, their daughters Maura and Ciara were born at AAMC.

Both girls are doing well and their brother seems to enjoy them, so far, Mr. and Mrs. Cronin said.

"But that's because they're not invading his space yet," Mrs. Cronin said, adding that the babies will be moved into Tadhg's current room because it has more space. "Wait until he's asked to play Barbies for the hundredth time, or dressed like a princess."

Victor Coward still is adjusting to life as a new dad. So much so that there is a crib in his Odenton home waiting to be assembled. He and Yvonne Borresen thought they had another two weeks before they went in for their scheduled C-section.

But the babies had other plans and Ms. Borresen went into labor Tuesday. At 10:20 p.m., 5 pound, 4 ounce Juliana Grace was born, followed by her brother, William Victor, 5 pounds, 2 ounces, a short time later.

The babies should be home this weekend.

Until the crib is put together, the siblings will sleep together in one crib, the new parents said.

Mr. Coward said he thinks Juliana takes after her mother, but he is not sure yet who his son resembles.

"We were very surprised and excited (when we learned we were having twins)," he said. "I've just been trying to get them to wake up enough to eat."