In her three years as an obstetrician and gynecologist in Brooklyn, Dr. Ngozi Nwankpa-Keshinro delivered several hundred babies, conducted several thousand pelvic exams and diagnosed everything from infections to infertility. But this year, with a little additional training, she has entered a new field: cosmetic medicine.

As one of the owners of a medical spa in Brooklyn that opened in January, she has given dozens of clients Botox injections to relax their wrinkles and Restylane injections to fill out their smile lines and plump their lips.

“The two fields are as alike as an apple and an orange,” Dr. Nwankpa-Keshinro said. “One can be lifesaving, while the other is not. But when you clear up someone’s acne or facial hair, they are as grateful as if you delivered their baby.”

Cosmetic medicine also provides a more relaxing lifestyle, she said. “And it’s very satisfying.”

Five years ago, cosmetic medicine was primarily the domain of plastic surgeons, facial surgeons and dermatologists — medical school graduates who undergo several years of training in facial skin and its underlying anatomy. But now obstetricians, family practitioners and emergency room physicians are gravitating to the beauty business, lured by lucrative cosmetic treatments that require same-day payments because they are not covered by insurance and by a medical practice without bothersome midnight emergency calls.