ART use is uneven across societies. Access varies by income and education, with some groups far more likely to undergo treatment than others. Even when someone has a child following the use of ART, it remains unclear what would have happened without treatment. Would they have conceived naturally later on? These uncertainties pose challenges to measuring and interpreting the contribution of ART to overall fertility.
Rising use of ART can also give a misleading impression of its overall impact on fertility rates, especially in contexts of declining natural fertility. If overall fertility falls, ART births will make up a larger share of all births, even if the absolute number of ART births is only modestly increasing. Conversely, because ART is needed by a relatively small proportion of the population, its contribution can appear negligible in population-level statistics, despite playing a crucial role for specific groups.
In a new study using 32 years of data from Norwegian Population Registers, Jenny Chanfreau (University of Sussex), Alice Goisis (University College London), and Øystein Kravdal (Norwegian Institute of Public Health) explore the challenges of conceptualising and measuring the contribution ART make to fertility rates.
Their findings highlight the importance of looking at differences across population subgroups, and of using both relative and absolute measures when assessing the contribution that ART makes to fertility. The relative contribution of ART–its share of overall fertility–was highest, rising sharply in recent years among women in their forties. In absolute terms, however, ART births were much more common among women in their thirties.
When the researchers analysed patterns of ART use by education and income, they found that while group differences in naturally-conceived fertility were either small or narrowing over time, disparities in ART-conceived fertility remained. Income-related differences remained consistently high over time, and educational gaps were widening.
The study also presents a thought-experiment: What would fertility rates have looked like if ART had not been available? The authors explored a range of scenarios to estimate ART’s “net” contribution. For example, if some people who had ART-conceived births would have eventually conceived without treatment, the overall impact of ART would be smaller. However, about one in four couples who have a first child through ART go on to have a natural conception. If ART enabled the first birth—and indirectly the second—its impact may in fact be greater than typically assumed.
The study raises important questions about how Assisted Reproductive Technologies are understood in both policy and academic contexts. Framing them as a solution to falling fertility tends to prioritise the fertility of more socially advantaged groups. The authors argue that clearer thinking around counterfactual assumptions, comparisons of different measures, and closer attention to differences across social groups are all needed. Showing both the relative and the absolute contributions of ART can help to clarify its role, while guarding against the misconception that ART can fully compensate for the postponement of childbearing to very late ages.