Labour leader David Cunliffe has taken responsibility for wording in his speech that claimed more parents would receive his planned $60 baby bonus than would actually get it.

"The buck stops with me," he said today, after yesterday saying he did not pen the line promising that "for 59,000 families with newborn babies, they will all receive a Best Start investment of $60 per week, for the first year of their child's life".

It turned out that about 25,000 people a year on paid parental leave, worth up to $488 a week, would not receive the payment at the same time.

Cunliffe hit another snag today when he could not explain the details of his policy on extending antenatal checks.

Cunliffe today went to a Trentham kindergarten, where he read a book on dinosaurs to children, to try to switch the focus on the early-childhood components of his policy released on Monday.

His policy promised "to ensure all women have access to free antenatal classes, with a focus on first-time mums and those who would benefit the most".

It said antenatal assessments would be available to all women at 10 weeks, and Labour would set targets for district health boards to deliver that.

The policy said vulnerable groups, including teenagers, were less likely to attend antenatal classes.

It pointed to a 2009 study that found 10 per cent of participants in antenatal classes were Maori and less than 1 per cent Pasifika.

Asked whether free antenatal classes was a new policy, Cunliffe said "free antenatal classes have been to some extent available".

"What we are being very clear about is that we will have them for all expectant mums," he said.

Labour would increase the target for 10-weeks checks to ensuring 80 per cent of mothers would get them.

Asked again whether antenatal classes were free to all mothers now, he said: "Not in every case, but I will have to check on the details."

He said his advice was that it was not generally freely available to everyone, but he could not say who would miss out.

Pressed on his knowledge of policy detail, he said: "When was the last time you asked John Key a question to five decimal places?"

The Ministry of Health's site makes it clear that free maternity and pregnancy services, such as 10-weeks checks, are available to virtually all, including those in the country on some visas.

But it says "there may be some charges for antenatal or childbirth education classes, and some tests at a private laboratory".