A woman who had sex with her nine-year-old son feels disgusted by her actions and blames a "cocktail of medication", her lawyer has told a court.

The 48-year-old cried in the dock of Sydney's Downing Centre District Court where she sat beside her husband, 57, who has also pleaded guilty to sexually assaulting the boy.

The couple, who cannot be named for legal reasons, are facing sentencing for the offences against their son, which occurred between January and November last year.

Some of the offences include streaming footage of the sex acts online.

The woman's lawyer Alex Morris cited a doctor's report that said her client suffered from a dependent personality disorder and referred to a "cocktail of medication to explain why she committed the offences".