Women with female infertility seeking medically assisted reproduction are not at increased risk of developing multiple sclerosis.

STUDY QUESTION: Is female infertility among women seeking medically assisted reproduction (MAR) associated with prevalent as well as incident multiple sclerosis (MS)? SUMMARY ANSWER: Women with a record of female infertility did not have an increased risk of developing MS compared with apparent fertile women; however, the prevalence of MS was slightly higher among women undergoing MAR compared with women who had a child without MAR, but this was not related to origin of infertility (i.e. male versus female factor infertility). WHAT IS KNOWN ALREADY: Women with MS have fewer children compared with women without MS. Persons with MS more often have other coexisting autoimmune disorders including hypothyroidism compared with the general population. Thyroid dysfunction is associated with ovarian cause of infertility, miscarriage and ovarian failure. Conversely, women with endometriosis, that is highly associated with infertility, also more often have other coexisting autoimmune diseases including MS and hypothyroidism compared with the general population. However, whether the low fertility rate among women with MS is due to a genetically predisposition to other autoimmune and endocrine disorders that leads to reduced fertility, or an active choice of the woman, disease-related pathology or treatment-specific effect on endocrine and/or ovarian function, is not completely understood. STUDY DESIGN, SIZE, DURATION: A register-based cohort study of a total of 310 357 women from 1996 to 2018. A cross-sectional design was used for analysing prevalence of MS, whereas a cohort design with up to 24 years of follow-up was used for analysing incidence of MS. PARTICIPANTS/MATERIALS, SETTING, METHODS: Three cohorts were included in the study (i) 55 404 women with a female infertility diagnosis registered in the Danish IVF register; (ii) 25 096 women with only male factor infertility recorded in the IVF register and thus no female infertility diagnosis and (iii) 229 857 age- and calendar-matched women with a record of first child birth in the Danish Medical Birth Register (DMBR) and no record ever in the IVF register. The prevalence and incidence of MS in the female infertility cohort were compared with the two control cohorts of apparent fertile women using log-binomial regression and Cox proportional hazard regression, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: The crude prevalence of having MS per 1000 persons was 3.2 for women who had undergone MAR treatment regardless of origin of infertility (i.e. male versus female factor infertility) and 2.3 for fertile DMBR controls. The age, calendar and educational level adjusted prevalence ratio of having a diagnosis of MS at the first MAR treatment was 1.27 (95% CI 1.07-1.52) for infertile women compared with fertile DMBR controls, and 1.00 (95% CI 0.77-1.31) for comparison to women with a male partner with infertility who had also undergone MAR treatment. We found no association between incident MS and female infertility compared with either of the control groups of fertile women. LIMITATIONS, REASON FOR CAUTION: The cohort of infertile women is highly selected on the basis of their choice of having fertility treatment and thus does not include women with unestablished infertility or women who, for some reason, have chosen not to have MAR treatment. Additionally, due to the nature of the observational study design, we cannot exclude the possibility of unmeasured and/or residual confounding. WIDER IMPLICATIONS OF THE FINDINGS: Our results suggest that women with MS may undergo MAR treatment more often than women without MS due to more awareness about the possibility of MAR treatments, sexual dysfunction related to MS disease, but also need for timing of the pregnancy to avoid an unnecessary long time period without disease modifying therapy-especially of high efficacy-and hence a wish to conceive quickly. These findings are important for clinicians dealing with women with MS of childbearing age. STUDY FUNDING/COMPETING INTEREST(S): The authors received no financial support for the study. T.I.K. has served on a scientific advisory board for Novartis and has received support for congress participation from Biogen. M.M. has served on scientific advisory boards for Biogen, Sanofi, Roche, Novartis, Merck, Abbvie and Alexion. She has received honoraria for lecturing from Biogen, Merck, Novartis, Sanofi and Genzyme and has received research support and support for congress participation from Biogen, Genzyme, Roche, Merck and Novartis. The remaining authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Assisted reproductive technology treatment and risk of breast cancer: a population-based cohort study.

STUDY QUESTION: Is there an increased risk of breast cancer among women after ART treatment including ovarian hormone stimulation? SUMMARY ANSWER: The risk of breast cancer was slightly increased among women after ART treatment compared to age-matched, untreated women in the background population, and the risk was further increased among women initiating ART treatment when aged 40+ years. WHAT IS KNOWN ALREADY: The majority of breast cancer cases are sensitive to oestrogen, and ovarian hormone stimulation has been suggested to increase the risk of breast cancer by influencing endogenous oestrogen levels. Previous studies on ART treatment and breast cancer have varied in their findings, but several studies have small sample sizes or lack follow-up time and/or confounder adjustment. Recent childbirth, nulliparity and higher socio-economic status are breast cancer risk factors and the latter two are also associated with initiating ART treatment. STUDY DESIGN, SIZE, DURATION: The Danish National ART-Couple II (DANAC II) cohort includes women treated with ART at public and private fertility clinics in 1994-2016. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with no cancer prior to ART treatment were included (n = 61 579). Women from the background population with similar age and no prior history of ART treatment were randomly selected as comparisons (n = 579 760). The baseline mean age was 33.1 years (range 18-46 years). Results are presented as hazard ratios (HRs) with corresponding CIs. MAIN RESULTS AND THE ROLE OF CHANCE: During follow-up (median 9.69 years among ART-treated and 9.28 years among untreated), 5861 women were diagnosed with breast cancer, 695 among ART-treated and 5166 among untreated women (1.1% versus 0.9%, P < 0.0001). Using Cox regression analyses adjusted for nulliparity, educational level, partnership status, year, maternal breast cancer and age, the risk of breast cancer was slightly increased among women treated with ART (HR 1.14, 95% CI 1.12-1.16). All causes of infertility were slightly associated with breast cancer risk after ART treatment. The risk of breast cancer increased with higher age at ART treatment initiation and was highest among women initiating treatment at age 40+ years (HR 1.37, 95% CI 1.29-1.45). When comparing women with a first birth at age 40+ years with or without ART treatment, the increased risk among women treated with ART persisted (HR 1.51, 95% CI 1.09-2.08). LIMITATIONS, REASONS FOR CAUTION: Although this study is based on a large, national cohort of women, more research with sufficient power and confounder adjustment is needed, particularly in cohorts with a broad age representation. WIDER IMPLICATIONS OF THE FINDINGS: An increased risk of breast cancer associated with a higher age at ART treatment initiation has been shown. Ovarian stimulation may increase the risk of breast cancer among women initiating ART treatment when aged 40+ years. Age-related vulnerability to hormone exposure or higher hormone doses during ART treatment may explain the increased risk. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by a PhD grant to D.V. from the Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. Funding for establishing the DANAC II cohort was received from the Ebba Rosa Hansen Foundation. The authors report no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Assisted reproductive technology treatment and risk of ovarian cancer-a nationwide population-based cohort study.

STUDY QUESTION: Does hormone stimulation during assisted reproductive technology (ART) treatment increase the risk of ovarian cancer? SUMMARY ANSWER: No increased risk of ovarian cancer was found among ART-treated women, with the exception of ART-treated women with endometriosis. WHAT IS KNOWN ALREADY: Previous studies on the association between ovarian stimulation during ART and ovarian cancer have shown conflicting results. The risk of ovarian cancer varies according to the cause of infertility, and only a few studies on ART treatment and risk of ovarian cancer have had sufficient data to address this issue. Endometriosis has been linked to an increased risk of ovarian cancer. STUDY DESIGN, SIZE, DURATION: Women undergoing ART treatment during 1994-2015 were registered in the Danish IVF register. Data were linked with data from the Danish Cancer Register and socio-demographic population registers using an individual person identification number assigned to people residing in Denmark. PARTICIPANTS/MATERIALS, SETTING, METHODS: All women undergoing ART treatment were age-matched with a random sample of the female background population and followed for up to 22 years. After relevant exclusions, the population consisted of 58 472 ART-treated women and 625 330 untreated women, all with no previous malignancies. Ovarian cancer risk was assessed using multivariable cox regression analyses with adjustment for educational level, marital status, parity and treatment year. Results are shown as hazard ratios (HRs) with corresponding CIs. MAIN RESULTS AND THE ROLE OF CHANCE: In total, 393 (0.06%) women were diagnosed with ovarian cancer during follow-up (mean 9.7 years). Women treated with ART had an increased risk of ovarian cancer (HR 1.20, 95% CI 1.10-1.31), which diminished over time. The increased risk was apparent among women with female factor infertility (HR 1.36, 95% CI 1.25-1.48), whereas no female factor infertility was associated with a lower risk (HR 0.87, 95% CI 0.76-1.00). The risk was increased among women with endometriosis (HR 3.78, 95% CI 2.45-5.84), whereas no increased risk was found among ART-treated women with polycystic ovary syndrome, other female causes of infertility and unexplained infertility. LIMITATIONS, REASONS FOR CAUTION: The association between ART treatment and ovarian cancer is likely influenced by increased detection due to multiple ultrasound scans during ART treatment. WIDER IMPLICATIONS OF THE FINDINGS: Undergoing ART treatment without the presence of endometriosis was not associated with an increased risk of ovarian cancer, which is reassuring. Whether ART treatment increases the risk of ovarian cancer among women with endometriosis needs further investigation. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by a PhD grant to D.V. from the Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. Funding for establishing the Danish National ART-couple II cohort was achieved from Ebba Rosa Hansen Foundation. The funders had no influence on data collection, analyses or results presented. The authors have no conflicts of interest to declare.