Deciding to have children had become more of an economic decision, Ms Pankhurst said.
Having more than two meant having to upgrade to a people mover vehicle, a bigger house and higher school fees.
"All those things together start to matter collectively."
Women did not necessarily want to put the time and money into getting a good education, then have to stop and have children. We have a choice about that. All those things are impacting the declining birth rate.
"If we had an aging population and an accelerating birth rate, there wouldn't be a problem but because both of those things are now negative, it's not healthy."
Ms Pankhurst highlighted a Treasury report about the country's aging population that said in 1960, there was an average four children per family. In 1980, this had fallen to two and this was a trend predicted to continue.
People also lived 10 years longer than they did 50 years ago.
Tauranga mother Jennifer Hill said there were several factors involved in her decision to wait to have children. "I was 36 when I had my daughter. I didn't actually meet her father until I was 32 and then we moved to Australia so it just took us a while to get round to it," she said.
"Even if we had met earlier, I still think I would have waited until I was thirty something. I was just a bit of a late developer, I was having a good time."
At the Pregnancy Choice Centre, Janice Tetley-Jones said she had not noticed a decrease in births, but she had noticed more people seeking to adopt or whangai (family members as foster parents) out their children.
"I've been doing this for 23 years and this is the first year I've noticed an increase in women who are prepared to go through with their pregnancy and adopt or whangai."
Mrs Tetley-Jones thought this could be because more women were becoming aware of the potential fertility issues if left too late. Adoption was also less taboo than before.
"Adoption has changed so much. It's so much more open, mums can stay in contact with their babies and visit them."
Tauranga LMC midwife Gillian Sims said she had not seen any decrease in births.
"February has been a manic month for me."
- Additional reporting NZME.