The first person to face court in NSW for alleged female genital mutilation could be retried after a jury failed to reach a verdict.

The jurors - five women and seven men - deliberated for more than 12 hours, but told the District Court in Sydney it would be "absolutely impossible" for them to agree unanimously.

The doctor standing trial, who cannot be named for legal reasons, surgically removed about 60 square centimetres of Carolyn DeWaegeneire's genitals - including her clitoris - by performing a vulvectomy.

He was charged under Section 45 of the Crimes Act, which outlaws female genital mutilation and carries a maximum prison sentence of seven years.

Then 58, Mrs DeWaegeneire was referred to the rural NSW specialist in 2002 with a pre-cancerous lesion on her vulva, measuring roughly two centimetres by 2½ centimetres.