Beaujouan, Reimondos, Gray, Evans and Sobotka (2019) showed, using two waves of the Australian HILDA survey, that women with a strong short-term intention to have a child become progressively less likely to realise it from about age 35 onwards, while for men the age effect is weak; but their data could not show why intentions fail. The open problem is to disentangle and quantify the relative contributions to this non-realisation of (i) biomedical factors (age-related decline in fecundity, miscarriage, and the use and effectiveness of assisted reproductive technologies), (ii) behavioural responses (attempting to conceive, seeking medical treatment), and (iii) socio-economic and normative factors (partner availability, partner characteristics including within-couple age differences, education, and perceived social age deadlines), over follow-up horizons longer than the four years available to the original study. Later work has mapped parts of this question cross-nationally — notably the gap between fertility intentions, pregnancy attempts, and births across reproductive ages — but no study has yet delivered the decomposition itself, because no dataset combining measured intentions with treatment records, couple-level information, and extended follow-up has been analysed.

Background

In demography, fertility (or reproductive) intentions are respondents' answers to survey questions about whether they plan to have a child within a stated horizon (typically three years); 'strong short-term intentions' are certain, short-horizon positive answers. Realisation means that a birth actually occurs within the horizon, and the intention–behaviour gap is the well-documented fact that intentions predict births only imperfectly. Non-realisation is the absence of such a birth within the horizon; intention abandonment is the downward revision in which a respondent no longer strongly intends to have a child at the follow-up wave, so abandonment is a component of non-realisation (whose remaining component is intentions retained without a birth) rather than a separate, parallel outcome. The Household, Income and Labour Dynamics in Australia (HILDA) survey is a nationally representative annual household panel; the Generations and Gender Survey (GGS) is the main comparative European panel on family formation. Assisted reproductive technology (ART), also called medically assisted reproduction (MAR), comprises clinical treatments such as IVF. Natural fecundity (the monthly probability of conceiving) declines through a woman's thirties and drops steeply after 35, while miscarriage risk rises; combined with the widespread postponement of childbearing, this raises the risk that late childbearing plans are not realised.

A sizeable literature predating and surrounding the source study examined realisation of short-term intentions: Dommermuth, Klobas and Lappegård (2015) compared realisation across intention time frames in Norway; Kuhnt and Trappe (2016) identified channels of social influence on realisation in Germany; Kocourková and Šťastná (2021) compared the realisation of intentions at later childbearing ages in Czechia and France within the postponement transition; Brzozowska and Beaujouan (2021) documented comparability pitfalls of GGS intention questions and analysed realisation for women and men at prime and late reproductive ages. Against this background, Beaujouan and colleagues (2019) asked how the likelihood of having a child within four years varies with age among respondents with strong short-term intentions (HILDA 2011 to 2015; 447 men aged 18–45 and 528 women aged 18–41). They found a steep decline in realisation for women from age 35, a weak and non-significant age gradient for men, the highest plan-abandonment rates among women aged 38–41, and the highest realisation among married and highly educated respondents and those with one child. Crucially, the survey recorded neither treatment use nor the reasons for non-realisation, so the study could not separate the three candidate explanations: biomedical obstacles (infertility, miscarriage, ART use and its effectiveness), behavioural responses (whether and how persistently people attempt to conceive or seek treatment), and socio-economic or normative influences (partner availability and characteristics, within-couple age differences, education, and social age deadlines — shared expectations about ages beyond which childbearing is no longer appropriate). The study also covered only a four-year follow-up, leaving open how retained late intentions evolve and whether treatment eventually converts them into births.

Problem Statement

For women and men who state a strong short-term intention to have a child — especially at higher female ages, where realisation declines steeply — determine the relative contributions to non-realisation and to intention abandonment of three overlapping channels (a mechanism such as assisted-reproduction uptake or treatment-seeking may therefore contribute through more than one channel): (1) biomedical causes, including age-related infecundity, miscarriage, and the uptake and effectiveness of assisted reproductive technologies; (2) behavioural responses, including whether, when, and how persistently individuals attempt to conceive and seek medical treatment; and (3) socio-economic and normative influences, including partner availability, partner characteristics and within-couple age differences, education, and perceived social age deadlines. The question includes how these contributions vary by sex, age, and their interactions (for example age with partnership status or education), and how they play out over follow-up horizons longer than four years, including late realisation of retained intentions and the long-run effectiveness of treatment. Identifying each channel's contribution requires data and a design that can separate the channels — records of intentions together with treatment use and/or reasons for non-realisation, and couple-level measurement of both partners — and an analysis that quantifies the relative contributions with uncertainty, stating which contributions the design identifies and which remain unidentified.

References

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