WASHINGTON — A procedural vote on a Senate bill to ban abortions after 20 weeks failed on the evening of Jan. 29, after more than three hours of debate. The cloture motion, which would have prevented a filibuster on the bill, required 60 votes to pass and failed by a vote of 51-46.

The bill will continue to be considered in the Senate and is widely expected to be a topic of debate in 2018 Senate elections.

The United States is one of seven countries in the world that allow abortions after five months of pregnancy.

The Pain-Capable Unborn Child Protection Act proposes that abortion be made illegal after 20 weeks of gestation, on the basis that fetal neural development enables the unborn to experience pain at that point. The bill includes exceptions for an abortion in the case of rape or incest, as well in the circumstances in which the pregnancy threatened the life or the mother.

“After 20 weeks, the unborn child reacts to stimuli that would be recognized as painful if applied to an adult human, for example, by recoiling,” according to the text of the Pain-Capable Act.

Twelve Democrats claiming to be Catholic voted against the bill: Maria Cantwell (WA), Dick Durbin (IL), Kirsten Gillibrand (NY), Heidi Heitkamp (ND), Tim Kaine (VA), Patrick Leahy (VT), Ed Markey (MA), Cortez Masto (NV), Claire McCaskill (MO), Bob Menendez (NJ), Patty Murray (WA) and Jack Reed (RI).

Because of an unborn child’s sensitivity to pain at this stage, anesthesia is regularly administered during in-utero surgery after 20 weeks. An ultrasound can reveal the gender of an unborn child, who can be viewed sucking his or her thumb, yawning or stretching by 20 weeks of pregnancy. The nervous system begins functioning in the fourth month of pregnancy.

The bill, which was passed by the House of Representatives in October 2017, is opposed by most Senate Democrats. To prevent a filibuster, Republicans needed Democratic support, in addition to the votes of the 51 Republican Senators.

Democratic Sens. Bob Casey, Joe Manchin and Joe Donnelly supported the motion. Republican Sens. Susan Collins and Lisa Murkowski voted against it.