A GP who spoke to a mother five days before she killed her children had not seen a letter raising concerns about her suicidal thoughts, a coroner heard.
Samantha Ford drowned her 23-month-old twins and tried to take her own life on 26 December 2018.
Her doctor had not seen a warning from a mental health team when they met on 21 December, an inquest heard.
Ford was jailed for 10 years in August 2019 after admitting manslaughter by diminished responsibility.
Dr Robert Immelman told an inquest in Maidstone that Ford appeared "calm and focused" when they met to discuss extending her prescription for anti-depressants.
Had he seen the letter, he said the "consultation would have taken a completely different pathway" and he would have carried out a "mental health risk-assessment".
The letter raising concerns about suicidal thoughts was sent to the Charing Practice on 14 December, but had not been put in the GP's notes on the practice system, the court heard.
Twins Jake and Chloe spent Christmas Day with their father Steven Ford, but were returned to their mother at her home in Margate the following day.
At about 18:25, she undressed them and then held them under water in the bath, the inquest heard.
She then left a note on the kitchen table, the inquest heard, written in pink crayon and saying: "Please forgive my crazy mind".
Mrs Ford drove to Beachy Head, before returning to the Margate area where at 02:48 she drove into the back of the truck at about 100mph (160km/h) on the A299.
She told the police officers who helped rescue her: "I have killed my babies".
The children were found in bed at the house and taken to hospital where they were pronounced dead.
Coroner Christopher Sutton-Mattocks said the inquest would consider the interactions Ford had with healthcare professionals before the children's deaths.
Mrs Ford's mental health had deteriorated following the break-up of her marriage to the children's father, the inquest heard.
The couple had lived in Dubai and Qatar, before moving to Charing in Kent in 2018.
Samantha's mother Collette Emptage said in a statement that her daughter had not wanted to move back to the UK from Qatar and she worsened after she moved into rental accommodation with the children after the break-up.
The inquest continues.