The three branches of the armed forces will begin next month charting the care that pregnant women receive in military hospitals as part of a year-long study prompted by a consultant's report critical of Air Force obstetrical care.

Dr. J. Jarrett Clinton, deputy Defense secretary for professional affairs and quality assurance, said yesterday that each service will record births, note complications that occur during those births and follow the progress of each mother and child for six weeks.

Each service will analyze the data it collects and one branch will prepare an overall report, Clinton said.

"We want to see if obstetrical care here is consistent with what is happening elsewhere . . . the odds are that it won't tell us anything we don't know about how we deliver babies. We do an outstanding job," Clinton said.

Obstetrics is among the most common forms of medical care provided by military hospitals. According to an independent study of Air Force data in 1982, childbirth accounted for 12 percent of all admissions.

Health Data Institute Inc., which compiled the study for the Defense Department, raised questions about the rate of complications that occurred during births at Air Force hospitals in 1982.

According to its survey, the rate of severe tears and cuts during delivery was occurring at twice the national rate of 20 to 22 per 1,000 births. That data revealed a "pattern of probable poor performance," Health Data Institute said.

Defense analysts later criticized the report, saying it was based on inconsistent hospital records and conflicting definitions of postsurgical complications. Yesterday, Defense personnel said the three services agreed to the internal study because they are "anxious to show that they have better care than the HDI study showed."

"If there's a difference among the three services, it will be debated," said Clinton, adding that the results from the three services will be published. "We'll be looking at the outcome to see what happened to mom, what happened to baby."