LINCOLN - Twenty state legislators joined Sen. Julie Slama in introducing a bill in Nebraska’s 107th Legislature to adopt the heartbeat act that bans abortion after a fetal heartbeat is detected.

The act will require physicians to perform an ultrasound to determine if there is a heartbeat prior to an abortion. Physicians can usually detect cardiac activity at about six weeks.

Violations will be a class 3A felony, but the act says the existence of a medical emergency is a defense. Mothers can not be prosecuted under the act, but abortions after a heartbeat is detected would be “unprofessional conduct" on the part of the provider.

Slama introduced LB 781 on the first day of the Legislature.

In a tweet, Sen. Slama said the bill has a chance of passing as there are 33 state senators who are consistently pro-life, which is needed to defeat a filibuster.

Sen. Megan Hunt of Omaha has vowed to resist restrictions on abortion rights. She introduced a bill that will allow advanced nurses, physician assistants and certified midwives to offer abortion services.