The impact of assisted reproductive technology for second births: a follow-up study

Abstract Study question What is the probability and the modality of conception of a second birth according to the modality of conception of the first one? Summary answer Assisted reproductive technology (ART) plays a minor role in the achievement of second births and the fulfilment of the desired family size. What is known already Although fertility rate has been declining and is currently at 1.30, the number of desired children of Italian couples is reported to be at two. Moreover, the desire for children is high even after the age of forty. Recent evidence suggests that ART mainly helps women to obtain their first child, rather than satisfying the desired family size. However, evidence regarding the rate of women who underwent ART and returned to ART centres for other children is very limited and the role of ART in fulfilling couples’ reproductive intentions is a challenging issue to investigate. Study design, size, duration We conducted a population-based study based on administrative data from regional healthcare databases of Lombardy Region, including 431,333 first deliveries conceived naturally and 16,837 first deliveries occurred after ART between January 1st, 2007 and December 31st, 2017. The probability of a second live birth was longitudinally assessed up to 2021. Participants/materials, setting, methods The probability of a second delivery after a natural or medically induced pregnancy, stratified by maternal age at first birth, was estimated with the Kaplan-Meier method. Cox proportional hazard models were fitted for estimating the hazard ratio (HR) and 95% confidence interval (CI) of the association with the mode of conception of the first pregnancy. Right censorship occurred if a woman moved out of region, died, or did not deliver by the end of follow-up. Main results and the role of chance The probability of a second birth after a first pregnancy with ART was half of that observed in women with a previous natural pregnancy, being 32.1% and 58.6%, respectively (HR = 0.68, 95%CI:0.66-0.70). The probability to have a second natural pregnancy in women who conceived naturally was 59.3%, while 1.1% had ART. However, among women who conceived with ART the probability of a new spontaneous pregnancy was also higher (25.2%) compared to those who had a baby with ART (11.5%). Natural pregnancy after a first successful ART attempt was overall less frequent than a second natural conception in fertile women. Thus, a consistent proportion of infertile women did not achieve the most common intended number of children. Determinants of this results could not be reliably assessed with our study. Limitations, reasons for caution We have no information on women who underwent ART and failed; this may underestimate of the actual return rate to ART. Furthermore, we do not know if women changed the partner between the first and second child. Wider implications of the findings In the ART field, more attention should be given to satisfy the desired family size, as the main goal is to not only reduce childlessness. Studies are warranted to reveal the determinants behind the infrequent return to ART. Identifying possible solutions could help women achieving their intended number of children. Trial registration number not applicable