Hannah Rankin failed in her attempt to add the interim WBC super-welterweight title to her IBO belt after losing to Sweden's Patricia Berghult on points.
The 29-year-old Scot faced an uphill battle after being knocked down in the first flurry of punches in Malta. The former Hermitage Academy pupil lost out to the Swede on a unanimous points decision after the bout in Malta on Wednesday night.
Rankin who was recently named Scotland's sportswoman of the year, was also bidding to add the interim WBC super-welterweight title to her crown recovered following a standing eight count, but it allowed her unbeaten opponent to protect her lead on the judges' scorecards.
They scored it at 96-93, 94-93, 95-94 for Berghult at the end of the 10 rounds.
The 25-year-old Swede, who has now won all 14 of her professional bouts, said: "I cannot believe it. Hannah is a really good, tough opponent. All respect to her."
For Rankin, who was crowned Scotland's first female world champion with a unanimous points decision over the USA's Sarah Curran in June, it was a fourth defeat in 12 fights.
Rankin looked to take the fight to her opponent from the first bell, but as she went on the offensive, she was floored by a left hook.
Berghult has a reputation for starting quickly, establishing an early dominance and then frustrating her opponents and, although the Scot recovered her composure, the Swede was keeping her at bay with a dominant jab.
Rankin came to life in the third and fourth rounds, but by the fifth, all three judges gave Berghult a comfortable lead.
The Scot responded by attempting to apply more pressure in the sixth, only to be regularly picked off, and looked to be struggling to work out her opponent in a more cagey seventh.
Despite Rankin looking increasingly frustrated, one judge had the opponents tied by the end of the eighth round.
The Swede was trapped on the ropes in the ninth, but Rankin's hopes of a telling blow were dashed as it was only the result of her opponent's slip and the referee stepped in.
Realising she was still behind, the Scot came out for the final round determined to throw more punches.
She caught her opponent with one superb right hand, but Berghult survived and matched that with some telling punches of her own as Rankin became more desperate and the Swede secured a deserved victory.
Rankin's management company, Kynoch Boxing, said in a post on Instagram after the contest: "Hannah got off to a terrible start - suffering a knockdown in the opening seconds.
"A poor second round followed but Hannah then regrouped and we thought she did enough to narrow the gap at the end to merit a draw.
"Congratulations to Patricia Berghult and her team. Full credit to her as she boxed an excellent fight.
"Hannah has the heart of a lion. She will regroup and bounce back from this setback."