A doctor, who said he is the best friend of a nanny accused of poisoning two baby girls under her care, told a district court yesterday that she had earlier sought treatment from a psychiatrist.

But Dr Peter Looi did not reveal what Sa'adiah Jamari, now 38, was suffering from at the time.

On the fourth day of the trial, Dr Looi told District Judge John Ng that he was working for Changi General Hospital's accident and emergency department at the time of Sa'adiah's alleged offences.

He added: "I would say I am her best friend. I've been her mentor, her adviser, her confidant, her doctor - and I know a fair bit of her life."

The court heard that the two have had this relationship for at least 15 years.

Sa'adiah is accused of two counts of administering medication or "poisons" to the babies with the intention of hurting them.

One of the infants was just five months old, while the other was 11 months old. They are not related to each other.

The Singaporean freelance nurse allegedly committed the offences in November and December 2016.

Sa'adiah is accused of giving the babies medication such as sleeping drug zolpidem, antihistamine chlorpheniramine, muscle relaxant orphenadrine, as well as alprazolam and diazepam, which are used to treat anxiety disorders.

Yesterday, Dr Looi told the court that he had passed Sa'adiah "simple flu or cough" medication when she was unwell. He testified that he could "possibly" have given her chlorpheniramine for a runny nose, as well as orphenadrine, but said he had never given any drugs to the two babies.

He also said that he had never given Sa'adiah sleeping pills or sedatives.

Dr Looi told Judge Ng that Sa'adiah's psychiatrist had given her some of the medication. He did not say which ones.

The court had heard earlier that Sa'adiah had been prescribed the substances later found in the infants' bodies.

On Dec 29, 2016, items including an empty pack of zolpidem, a handkerchief and a milk bottle were found in her Hougang flat.

Diazepam was later detected on the handkerchief, while the bottle had traces of zolpidem.

The 29-year-old mother of the younger baby had earlier testified in court that her child was hospitalised for several days after being found to be "very drowsy" and "cranky".

The 22-year-old mother of the older baby had also testified earlier that her child was hospitalised after Sa'adiah looked after her.

Both women cannot be named to protect their children's identities.

Sa'adiah is now out on bail of $10,000 and her pre-trial conference will take place on March 11.