One of the first and largest studies of its kind – drawing on data from thousands of kids here and overseas – suggests couples undergoing fertility treatment needn't fear for their children's development.
Since the first birth of a child by in vitro fertilisation (IVF), questions have been raised aboutthe risks to children conceived this way.
While previous research has shown an increased risk of low birth weight and preterm birth in offspring conceived by assisted reproductive technology (ART), relatively little has been known about long-term growth and weight gain.
In it, an international collaboration of scientists assessed whether conception by ART, which mostly involves IVF, was linked with differences in growth, weight, and body fat from infancy to early adulthood.
It drew on data from 158,000 European, Asian-Pacific, and Canadian children conceived by ART - including more than 6000 Kiwi children whose lives are being tracked under the longitudinal Growing Up in New Zealand Study.
Their findings showed that those conceived using ART were, on average, shorter, lighter, and thinner from infancy up to early adolescence, compared with their naturally conceived peers.
Yet those differences were small across all ages - and reduced with older age.
"Parents and their children conceived by ART can be reassured that this might mean they are a little bit smaller and lighter from infancy to adolescence, but these differences are unlikely to have any health implications," said the study's lead author, Dr Ahmed Elhakeem, of the University of Bristol.
"We acknowledge it is important that as more people conceived by ART become adults, we continue to explore any potential health risks at older age."
Dr Caroline Walker, a University of Auckland senior research fellow who collaborated on the study, noted that New Zealand had similar rates of infertility to the UK.
"In 2019 New Zealand fertility clinics reported nearly 8000 cycles of ART resulting in 1769 babies being born," she said.
"This equates to approximately three percent of births in any given year."
Walker also noted the value in having New Zealand data included in the study.
"Because Growing Up in New Zealand is following the lives of a large cohort from before they were born through to adulthood, we are able understand specifically how things like ART impact New Zealand children over a long period of time," she said.
"Studies like this enable us to speak more confidently about outcomes for these children in a local context," University of Auckland senior research fellow Dr Caroline Walker says. Photo / Supplied
"There are tens of thousands of children in New Zealand born as a result of fertility treatment and studies like this enable us to speak more confidently about outcomes for these children in a local context."
One Kiwi mum, whose now two-year-old son was conceived by ART, said she hoped the findings should offer some relief in what was often a stressful and costly experience for parents.
The 33-year-old suspected a long struggle with endometriosis had affected her own fertility – and it took four rounds of IVF, and plenty of heartbreak, before she and her partner had a baby boy.
All the while, she'd been aware of potential issues around development.
"Our boy was born quite skinny, and under four kilos at full term: but now our wee boy is very tall and very heavy, and weighs about 15kg."
The mother, who asked to be known only as Jane, said couples undergoing IVF treatment also faced much stigma from the public.
"I want this whole process to be normalised – and for people to seek help if they're struggling," she said.
"It's nothing to be ashamed of."
Dr Andrew Murray, group medical director at Fertility Associates, also welcomed the findings, which followed similar research that suggested no increased incidence of cancer or fertility issues among IVF-conceived people.
"A common question we get asked from time to time is, are there any risks going through this treatment compared with conceiving naturally," Murray said.
"So, it's fantastic we now have these large studies to back what our impression has been all along: that the techniques are safe, and that the children at the outcome of this treatment are healthy."
