SAN DIEGO — They used to ring a bell at the Naval Medical Center each time a baby was born. And every baby's name was printed in the base newspaper.

No time for such niceties anymore. A baby boom is under way.

Births among the Navy and Marine Corps wives who come to the center for delivery are up 20 percent since the United States launched its war on terrorism in late 2001.

Naval Medical Center San Diego has the busiest delivery rooms of any Navy hospital in the U.S., averaging about 350 babies a month, officials said. Before 9/11, the figure was about 288.

With many husbands overseas, the military tries to fill the role that a spouse might play. For each new mother, the Armed Services YMCA swoops in with a baby blanket, bonnet, birth announcements and information about support groups, including one for first-time mothers whose husbands are deployed.

For labor, delivery and postpartum recovery, all rooms are single-occupancy, except during peak times. The busiest times are nine to 10 months after troops return from an overseas deployment — not surprisingly.

Marisela Brittingham, 28, was two weeks overdue when she and her doctor decided on a Caesarean section. Her husband, Petty Officer 2nd Class Justin Brittingham, is on the carrier USS Ronald Reagan.

The sight of Justin Jr., at 7 pounds, 13 ounces, and 21 inches long, was more than Marisela could bear. "I cried when I saw him for the first time," she said in the recovery room.

The phone rang. It was her husband calling from the Persian Gulf.

"Where's he at?" he asked.

"He's here in my arms," she said. "He's been checked out: He's just fine."

Statistics about births in military hospitals do not include all babies born to military wives.

Some wives go to private hospitals. Many younger wives return to their parents' homes when their husbands deploy, and give birth at local hospitals. Because the families of National Guard and Reserve soldiers generally do not live on bases, those births are not recorded by military hospitals.

Still, the boost in births among the wives of active duty troops after a deployment has been noted by officials at base hospitals at Camp Lejeune, N.C.; Fort Bliss, Texas; Fort Bragg, N.C.; Camp Pendleton; Twentynine Palms base and Fort Campbell, Ky.

Many battalions are on a rotation known as "seven-and-seven": seven months in Iraq, seven at home, then seven more in Iraq, with no end in sight. For husbands and wives, that uncertainty can lead to soul-searching about starting a family.

"We made it through one deployment with no problem, but then we figured, 'Should we tempt fate? What if something happens this time?' " said Meredith Simpson, 25, whose husband, Lt. Neal Simpson, is an infantry officer.

The Simpsons decided not to wait. She gave birth at the hospital at Camp Pendleton to twins. Her husband was on the phone from Fallujah, Iraq, during the 14 minutes between the arrival of Connor and of Grayson.

Leanne Doring's husband, Gunnery Sgt. JohnPaul Doring, has completed two tours in Iraq. Both of the couple's children were born while he was away.

Although it is difficult to be pregnant while your husband is away, said Leanne, 36, there is joy at the end. "It's a beautiful thing to hand your husband his child when he gets off that bus," she said.

"A war makes you realize your own mortality," she added. "The children are the best part of what our husbands leave behind when they go away to war."