Doctors inserted one or two small Jadelle rods into a person's arm and progesterone was released into the bloodstream for three to five years, preventing the ovaries releasing an egg each month.
Some were doing their own thing, possibly travelling, building their careers, or establishing a home first, and making sure they were financially better placed before deciding to start a family.
Since the Government began subsidising Jadelle in 2010, teen pregnancy rates have dropped 37 per cent throughout the country, and better health education around contraception had an effect on the teen pregnancy rates.
Te Whakatipuranga School for Young Parents, run by Otumoetai College but held at the Bay of Plenty Polytechnic, had also noted a trend of fewer teenage mums coming through the school.
Otumoetai College principal Dave Randell said the school had been operating it for about 10 years, and had guaranteed funding for 35 students, but the number of teenage mums coming through the school in the past three years had dropped year on year.
Robyn Merritt, teacher in charge at Te Whakatipuranga, said at any given time there were 25 to 30 students at the school, and during last year a total of 50 students attended, but not for the full year.
We are certainly aware of a decrease in teenage pregnancies, which was primarily due to better long-term contraception.
So far this year there were 26 students enrolled, she said.
Viv Edwards, Plunket's central region clinical services manager, said: "We are certainly aware of a decrease in teenage pregnancies, which was primarily due to better long-term contraception."
Ms Edwards said the increasing number of women delaying parenthood was due to a number reasons, which included building their careers, financial or relationship reasons, and some would also be due to health or fertility difficulties. "Most important is that the environment is right to promote a positive pregnancy and parenting experience so the child is welcomed into the home when all these things are in place," Ms Edwards said.
Tauranga Hospital also had an increase in the number of women over 40 giving birth, steadily rising about 40 per cent in the last 15 years.
College of Midwives midwifery advisor Lesley Dixon said waiting until later in life to have children was becoming more common.
Ms Dixon said advances in fertility treatment comforted those worried about struggling to get pregnant naturally as they got older, she said.
"Women are focusing on their careers as a first step and then thinking about having children later ... There's more support from IVF to become pregnant. In most developed countries women are delaying having children, which means some mothers will become pregnant in their forties."
Mr Randell said at his college the five teachers on maternity leave were all in their 30s, and included some first-time mums.
"There is a definitely a trend of women deciding to delay having children until older. Some were doing their own thing, possibly travelling, building their careers, or establishing a home first, and making sure they were financially better placed before deciding to start a family."
Across the country, mothers over the age of 40 giving birth had jumped 250 per cent in the last 25 years, and mothers over 45 years old had tripled in the same period.