Taking on motherhood later in life is becoming more common in New Zealand - with figures for last year showing that for the first time women in their late 30s had more babies than those in their early 20s.
The jump in births for the older group was in line with an increasing trend of older mothers, experts said, with many women choosing to wait to have children until they were better settled in their career.
Professor Wayne Gillett of the Otago University medical school said that while many people were aware of decreasing fertility rates for women in their 30s, trying for a second or third child was often the major challenge for people in this age group.
"The real number one issue for these people is that they won't have the family size that they've anticipated at the end of the day.
"It's because of increasing fertility problems as they get older."
Women were most fertile between 20 and 30, said Professor Gillett, who is head of the women's and children's health department at the medical school.
At 35, a woman was about half as fertile as she was before hitting 30, and by 40 this dropped to about a fifth.
Provisional research figures also indicated about 25 per cent of women who tried for babies after 35 were unsuccessful, he said.
In addition to this, from the age of 35 to 39, the risk of fetal anomaly and congenital abnormalities such as Down Syndrome "escalated quite quickly", Professor Gillett said.
Psychiatrist Dr Haluk Aydin said parents who chose to wait until they were older to have children were often better equipped to deal with the challenges of parenthood.
"If parents were older, they might be more mature and maybe able to handle themselves better.
"Younger parents might be more lively and more energetic ... but older parents might be more resourceful."
Older parents were also more likely to be better placed financially, with more time for work and studies before they had a baby, he said.
Executive coach Jayne Muller, who specialises in helping individuals stay on top of their careers while taking time out for parenting commitments, said workplaces could be difficult to navigate for new parents.
"The majority [of women] that I work with are definitely wanting to get their career established.
"They get to a certain level and think, 'I need to start to think about having kids, I'm in my 30s'."
Attitudes of prejudice around maternity and parental leave still existed in many workplaces, she said.
One woman she worked with, who was also on the company's talent programme, was told she was committing career suicide when she revealed her second pregnancy, Mrs Muller said.
"Sadly, it still happens a lot more than you think. It's mostly around flexible working."
Statistics New Zealand says women aged 35-39 had the most babies in 2013.
Mum: I knew time was ticking
Tolotea Lanumata, 39, recently celebrated her daughter Luseane's third birthday.
A visit to the doctor about four years ago revealed the then 35-year-old was unable to conceive naturally.
To help her get pregnant, she took hormone treatments.
"She was kind of half unplanned ... but I was also over 35 and I was starting to become conscious about my biological clock."
The PHD student, who is on track to finish her studies in June, returned to her research about six months after she gave birth in February 2011.
"It was part-time, but it was hard leaving her to come back to school.
"My supervisor was very supportive because she was the one who suggested I check with a doctor as to whether I'm able to have children or not."
The Wellington resident said it took about a year before she got back to a full workload.
Having support from her peers, friends and family had helped with her daughter.
"She's at kohanga now. I'm a single mum. Things happen and you just go with it."