Minor changes in the incidence of primary and secondary involuntary childlessness across birth cohorts 1916 to 1975, but major differences in treatment success

There have been tremendous advances in assisted reproductive technologies (ARTs) over the past 50 years. The present study assessed infertility outcomes among women of reproductive age during this period. The seventh survey of the Tromsø Study (Tromsø7, 2015–16) recruited Tromsø residents aged 40–98 years. The questionnaire collected information on sociodemographics and infertility, as well as data from a wide range of validated health questionnaires. Primary involuntary childlessness was defined as reporting one or more of the following: the clinical definition of infertility (i.e., infertility period of >1 year), infertility examination, use of ART, and/or the birth of a child conceived during ART. Women with secondary involuntary childlessness were those who reported infertility experience and had least one naturally conceived child. Parous women without infertility experience were classified as fertile, and nulliparous women without infertility experience as voluntarily childless. The main exposure was birth cohort (1916–35, aged 80–98 years; 1936–45, aged 70–79 years; 1946–55, aged 60–69 years; 1956–65, aged 50–59 years; 1966–75, aged 40–49 years). The incidence of primary involuntary childlessness was significantly higher in the 1956–75 cohort (6.0%; 95% CI: 5.4–6.6) than the 1916–55 cohort (3.7%; 95% CI: 3.2–4.3). The incidence of secondary involuntary childlessness was higher than that of primary involuntary childlessness across all birth cohorts and was highest for the 1966–75 cohort (10%), with no differences observed across the other birth cohorts (6–7%). An increasing proportion of women from the oldest to the youngest birth cohorts reported infertility examination and ART. ART success increased substantially with time, reaching 58% for primary and 46% for secondary infertility in the 1966–75 cohort. Voluntarily childless women comprised 5–6% of the 1916–55 cohort and 9–10% of the 1956–75 cohort. There were minor differences in the incidence of primary and secondary involuntary childlessness across the 1916–75 cohorts. Advances in ART over the past 50 years comprised 2.0% and 3.3% of population growth in the 1956–65 and 1966–75 cohorts, respectively: a remarkable achievement.