COLUMBIA, S.C. (AP) — An appellate court is preparing to hear arguments over a lawsuit challenging South Carolina’s abortion law.

The court is set to hear arguments Thursday in Planned Parenthood’s case against South Carolina’s measure. The law requires doctors to perform ultrasounds to check for a so-called “fetal heartbeat,” which can typically be detected about six weeks into pregnancy.

If it is, the abortion can only be performed if the pregnancy was caused by rape or incest, or if the mother’s life is in danger.

Opponents say many women don’t know they’re pregnant at six weeks.

Medical experts say cardiac activity isn’t an actual heartbeat but rather an initial flutter of electric movement.