The survey shows 47 percent said they are pro-life and 45 percent are pro-choice.
This is the third consecutive time Gallup has found more Americans siding for pro-life than pro-choice since May 2009.
The pro-life side has maintained a lead in the poll for a year now, reaching as high as 51 percent to 42 percent last May.
Gallup said more Republicans and Independents have moved to the pro-life side. And the pro-choice label has become popular among Democrats.
The poll, which was conducted May 3-6, is based on phone interviews with 1,029 adults aged 18 and older.