He said it would be "very unwise" to take time off for childcare, and possibly would not be permissible under the Australian governing body's rules.
But an NZVA spokeswoman said as soon as the association was alerted to the ad it had spoken to the business involved and had the ad amended.
The paragraph about parental leave has since been removed.
Advertisers had full responsibility for their ads, but the NZVA tried to catch anything discriminatory before posting, she said.
"We need to be more vigilant but we're making a real effort to make sure discriminatory practices are not happening."
She said Robson was not an NZVA member but he "sort of understood the comments" criticising the post.
"I think in our way we're helping to educate the profession through our members but we may need to do a bit more in that regard to make sure everybody recognises that things have changed."
A spokeswoman for the Human Rights Commission said it had not received any complaints about the ad.
"Under section 67 of the Human Rights Act, it is unlawful to publish an advertisement which indicates, or could reasonably be understood as indicating, an intention to breach the unlawful discrimination provisions," she said.
"The commission doesn't make a ruling on whether there is a breach of the Human Rights Act but we would consider a complaint from a person who is qualified for the job, through our usual process."