The contribution of medically assisted reproduction to total, age-, and parity-specific fertility in Italy.

study questionWhat is the contribution of medically assisted reproduction (MAR) to total, age-, and parity-specific fertility in Italy? SUMMARY ANSWER: MAR contributed 3.7% to Italy's total fertility rate in 2022 and 5.9% to fertility of first order; MAR's contribution to fertility reached 16% among women aged 40 +  and 31% among women aged 40 +  at first birth. WHAT IS KNOWN ALREADY: Demography, particularly via postponement of the age at childbearing for both women and men, plays a role in the diffusion of MAR techniques, and the diffusion of MAR techniques may contribute to postpone the age at childbearing. Recent studies found that the contribution of MAR to fertility rates is remarkable and increases over time in countries such as Czech Republic, Denmark, Australia, and the USA. Italy is a country distinguished by one of the lowest average number of children per woman globally, as well as the highest maternal age at first birth and among the highest shares of births to mothers aged 40 years and over in Europe. No prior study has focused on Italy. STUDY DESIGN, SIZE, DURATION: This study relies on a unique combination of administrative data sources: the Certificate of Delivery Care Registry dataset based on the entire population of live birth deliveries in Italy in 2022 (N = 393 997), administered by the Ministry of Health; the Register of Live Births to the Resident Population in 2022 (N = 393 333), administered by the Italian National Institute of Statistics; and the resident population by age and sex to identify the female population at risk of having a(n additional) child by age (N = 17 006 665) provided by the Italian National Institute of Statistics. Comparisons are made with the year 2013. PARTICIPANTS/MATERIALS, SETTING,

methodsWe calculate the age-specific fertility rates (total and by parity) for births conceived via MAR and those conceived naturally. These rates are then utilized to assess the contribution of MAR to total and parity-specific fertility, as well as to the mean maternal age at childbearing. This study is the first estimation of its kind for Italy. MAIN RESULTS AND THE ROLE OF CHANCE: The contribution of MAR to the total fertility rate (for women aged 15-59 years) in Italy increased from 2.1% in 2013 to 3.7% in 2022. Among women aged 40 + , the contribution of MAR to the total fertility rate increases to 16.2% in 2022, up from 8.6% in 2013. The contribution of MAR to first-order fertility rate increases to 5.9% and it reaches 30.9% among women aged 40-59 years in 2022. The mean age at first childbirth among women who conceived via MAR equals to 37.8, up from 36.0 in 2013, compared to those who conceived naturally at a mean age at first birth of 30.4 in 2013 and of 31.3 in 2022. LIMITATIONS, REASONS FOR CAUTION: Our approach may underestimate MAR's contribution to the total fertility rate in Italy: mothers in Italy may be more likely to under-report of MAR-births than in other countries, due to social norms that are more resistant to non-conventional paths to parenthood. Our estimates use unconstrained denominators based on the entire population of women in reproductive age, irrespective of parity, to compute fertility rates because the population of women by age and parity is not available from official statistics. In addition, our estimates are somewhat affected by the possibility that couples who underwent MAR treatment would have eventually conceived spontaneously. WIDER IMPLICATIONS OF THE

findingsCountries characterized by low and late fertility offer a unique test ground for studying the contribution of MAR to fertility rates. In Italy, a late transition to parenthood among the general population aligns with the late transition to parenthood among mothers who conceived via MAR, mirroring that they seek infertility treatments at a relatively late age. For Italy, it will be important to monitor MAR's contribution to fertility as a new law came into effect in January 2025, that, by recognizing infertility as a pathology, considerably reduces treatment costs hence likely increases demand for MAR. The extent to which a potentially increased demand will translate into access to treatment is uncertain if additional resources are not made available to expand the health system to meet the expected increased demand. STUDY FUNDING/COMPETING INTEREST(S): We acknowledge funding from Next Generation EU, in the context of the National Recovery and Resilience Plan, Investment PE8-Project Age-It: 'Ageing Well in an Ageing Society' (DM 1557 11.10.2022) and the project 'ALFA-Aligning Law with Family Arrangements' funded by Fondazione Cariplo 2021-1321. Open access funding provided by University of Trento within the CRUI-CARE agreement. The views and opinions expressed are only those of the authors and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. No conflict of interest exists. TRIAL REGISTRATION NUMBER: N/A.