Correction: A previous version of this story incorrectly said that in 2010, two out of three enlisted female soldiers became pregnant while in the Navy. The data came from a 2010 survey, but the pregnancies occurred during the women’s full tenure in the Navy, not just that year. This version has been corrected.

Shortly after Bob MacDonald was hired by the Navy in 1999 to offer training in HIV prevention and treatment, he realized that sailors and Marines were not that interested in talking about sexual diseases. What they did want to discuss was unplanned pregnancy.

So MacDonald, a civilian who manages public health activities for the Navy, started collecting data on the topic. He discovered that rates of unintended pregnancy in the armed services were higher than he expected, given the medical attention and access to contraception available to sailors.

This was a big concern. Unplanned pregnancies and births were disrupting the working lives of Navy parents and straining their budgets as well as their health. Duty assignments were being rearranged and sailors were being removed from ships as their pregnancies progressed. Such adjustments might increase as more combat roles opened for women.

MacDonald, now 55, began to shape a sex education/sexual health promotion plan called SHARP, or Sexual Health and Responsibility Program. Under his direction since 2004, it has become the most comprehensive program of its kind in the military. Reducing unplanned pregnancies is its top priority, with lowering the rates of sexual disease a strong second. (The Army and Air Force run interventions for specific health concerns, such as the Air Force’s chlamydia program for women in boot camp. But neither offers a servicewide program like the Navy’s).

With MacDonald’s encouragement, the Navy revised training films to concentrate on the social consequences of unplanned pregnancy and the possible impact of it on a career. It replaced outdated films about sexually transmitted infections, shifting the focus from scare tactics (photos of genital lesions, for example) to advice on risk reduction.

MacDonald and others updated and expanded the Navy’s sexual health screenings and built a Web page that included downloadable resources on pregnancy and sexual disease. Sailors began being asked questions about sexual health in the service’s Web-based health risk assessment. The Navy Surgeon General’s office made sexual health criteria part of its annual health and wellness program for sailors.

With support from Navy brass, he became an outspoken champion for free and easy access to all forms of contraception. He is particularly enthusiastic about long-acting reversible contraceptives, or LARCs, such as the IUD and a hormone-releasing implant that prevents pregnancy for two years.

LARCs are 99 percent effective, which beats the 72 to 94 percent rate of methods such as the pill and the vaginal ring. But only about 15 percent of enlisted sailors use LARCs, so MacDonald began a promotional campaign in collaboration with the Navy’s Bureau of Medicine.

It’s too early to tell how well these efforts are working. What is clear is how serious an unintended pregnancy problem the U.S. military has. A study published in February in the journal Obstetrics and Gynecology found that about 11 percent of active-duty women ages 18 to 44, from all branches of the military, said they had had an unplanned pregnancy within the past year. This was a small increase from three years earlier and, adjusted for age, 50 percent higher than the rate for American women of similar age in the general population.

MacDonald, using data from a Navy survey, found similarly troubling trends. In an article this year for the journal Public Health Reports, he reported that according to a 2010 survey, two of every three enlisted female sailors became pregnant during their tenure in the Navy. Of those who got pregnant that year, 36 percent said their pregnancies were planned, a slightly lower proportion than in women of similar age in the general population. Navy officers fared better: 70 percent said their pregnancies were planned. There are about 52,000 women in the Navy and about 271,000 men.

Of particular concern to MacDonald were enlisted women ages 21 to 25. About half had been using no birth control prior to getting pregnant. A majority of these women said they had not used protection because they weren’t planning to have sex. Other women said they didn’t want to use birth control or their partners didn’t want them to.

“I have been in public health all my life,” MacDonald says. “Sexual health is more challenging than any other area.”

In terms of their sexual energy, young adults in military service are like young people in college and away from home for the first time. In the Navy, that energy may become particularly intense living in extremely close quarters for long periods, sometimes in dangerous circumstances.

They also may have trouble getting prescriptions refilled or accessing different methods of contraception while at sea.

Almost all women who get pregnant while in the Navy, whether intentionally or unintentionally, remain in the service before and after giving birth, according to Lt. Hayley Sims, a Navy public affairs officer. In light of that, the Navy recently designed a “family planning education encounter” that every sailor takes in boot camp. They learn about every form of reliable birth control and are offered a choice of contraception. Should they choose a long-acting form of contraception, they can go to a Navy clinic before deployment.

And after they’re deployed? Their new care providers may know Navy guidelines but be hesitant to bring up sexual matters until their patients do, MacDonald says. The health professionals need to get over that reluctance.

“ ‘Are you planning to have children?’ should be your first question,” he recently said during a webinar for health-care providers. “And ‘What are you doing to protect yourself?’ your second. Sailors are willing and ready to have a conversation about sex.”

Stepp is a former Washington Post writer.

For more information:

Navy and Marine Corps Public Health Center: med.

Reproductive and sexual health in the Navy:

CDC webinar on STDs in the military: