A Bethesda obstetrician was fined $1,000 in Montgomery County District Court yesterday and placed on probation before judgment--a sentence that means he may have no criminal record--in an assault case that resulted from an argument over a traffic incident on Christmas Day.

The obstetrician, Dr. Zakaria Mohamed Oweiss, 39, had been found guilty in April of assaulting Heather Cox-Carr of Bethesda, who was in the late stages of pregnancy and was being driven to Holy Cross Hospital in Silver Spring after experiencing apparent labor pains when the incident occurred.

At sentencing yesterday, Judge C. W. Woodward, who originally found Oweiss guilty, imposed the fine and six months' probation before judgment, which means that if the doctor is charged with no offenses in the next half year he will have no record of conviction.

The judge acted after defense attorney Steven A. Hamilton argued that Oweiss had no prior convictions and that the charge grew out of an incident in which he was defending himself in a fight.

Judge Woodward said he imposed the fine because of the seriousness of the incident.

The incident that led to Oweiss' prosecution occurred about 9 p.m. last Christmas on Cedar Lane in Bethesda near the Capital Beltway. Oweiss testified at his trial, according to court sources, that the car driven by Michael Carr, Cox-Carr's husband, was going too slowly and blocking his car. Oweiss stopped his car in front of Carr's, witnesses testified, and an altercation ensued, the sources said.

Oweiss was originally charged with assaulting both the husband and wife, but the judge found him innocent of assaulting Carr.

Carr was treated for nerve injuries after the incident and was in traction for 10 days, according to the court sources. His wife, who turned out to be experiencing false labor at the time of the incident, gave birth to a healthy son, Michael Jasu n Carr, At the Washington Hospital Center on Jan. 9.