For decades, researchers and physicians tended to think about pregnancies as either planned or unplanned. But new data reveals that for a significant group of women, their feelings don’t neatly fit into one category or another. As many as one-fifth of women who become pregnant aren’t sure whether they want a baby.

This fact may reshape how doctors and policymakers think about family planning. For women who are unsure, it doesn’t seem enough for physicians to counsel them on pregnancy prevention or prenatal care.

“In the past we thought of it as binary, you want to be pregnant or not, so you need contraception or a prenatal vitamin,” said Maria Isabel Rodriguez, an obstetrician-gynecologist at Oregon Health and Science University whose research focuses on family planning and contraceptive policy. “But it’s more of a continuum.”

The new data comes from a recent change in the Centers for Disease Control and Prevention’s big survey of new mothers, now allowing them to answer a question about their pregnancy desires by saying “I wasn’t sure.” It shows that some women want to avoid making a decision about becoming pregnant, or have strong but mixed feelings about it. A new analysis of the 2014 results from the Guttmacher Institute combined these results with data from abortion providers. It found that in 9 percent to 19 percent of pregnancies, the woman “wasn’t sure” what she wanted at the time.