Resolution of infertility and number of children: 1386 couples followed for a median of 13 years.

STUDY QUESTION: How common were children among infertile couples?

SUMMARY ANSWER: A total of 61.7% of infertile couples presenting for care subsequently had live born children 13.1 years after first being clinically assessed, with a mean of 1.7 children among those who had at least one.

WHAT IS KNOWN ALREADY: While the prognoses for infertile couples undertaking specific treatments have been well described, less is known about those not undergoing these treatments or the total number of children. This information is necessary for decision-making in many individual cases; not knowing this has been cited by patients and clinicians as impeding implementation of care.

STUDY DESIGN, SIZE, DURATION: The sole provider of specialist fertility care for the two southern-most regions in New Zealand enroled 1386 infertile couples from 1998 to 2005 in a longitudinal study with follow-up on all births until the end of 2014. Couples were followed in care for a median of 1.1 years and median follow-up for births was 13.1 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Clinic-collected data were linked to national maternity data to extend follow-up past the end of clinical contact. The primary outcome was the total number of live born children. Hurdle regression was used to investigate factors associated with resolving infertility and the total number of children.

MAIN RESULTS AND THE ROLE OF CHANCE: Infertility was resolved with a live birth by 61.7% (95% CI 59.1-64.2%) of couples; just over half of all first births were treatment-dependent. Among couples who resolved their infertility, 55.6% (52.2-58.9%) had at least one additional child and the mean number of children was 1.7. While female age strongly influenced outcomes, one-third of women aged 40-41 years had a child, not significantly less than those in their late 30s. The lowest levels of resolution occurred in women aged ≥42 years, couples who were infertile for >4 years and women with a BMI ≥ 35 kg/m2. Moderate obesity did not affect outcomes.

LIMITATIONS, REASONS FOR CAUTION: The main limitation of this study was insufficient data to investigate male factor infertility outcomes. It is also possible that treatment-dependent resolution could be higher in more recent cohorts with the increased use of ART.

WIDER IMPLICATIONS OF THE FINDINGS: Outcomes in these couples are comparable to those seen in other studies in high-income countries despite the relatively low contribution of ART. The prognosis for most infertile couples is positive and suggests many will not require treatment. Further research is needed to inform best practice for women in their early forties or with moderate obesity, and to develop prediction models that are more relevant for the initial management of infertility.

STUDY FUNDING/COMPETING INTEREST(S): This study was co-funded by a University of Otago PhD Scholarship and the Department of Women's and Children's Health, University of Otago. There were no competing interests to declare.