Type 1 diabetes risk in children born to women with fertility problems: a cohort study in 1.5 million Danish children

The risk of Type 1 diabetes in children born after ART: a Nordic cohort study from the CoNARTaS group

STUDY QUESTION

Do children born after ART have a higher risk of developing Type 1 diabetes (DM1) than children conceived without ART?

SUMMARY ANSWER

The risk of DM1 was similar for children conceived with and without ART, and there were no clear differences in risk according to method of fertility treatment.

WHAT IS KNOWN ALREADY

ART is associated with a higher risk of adverse perinatal outcomes, and the risk depends on the method of ART. The Developmental Origins of Health and Disease theory proposes that prenatal stress can provoke changes in endocrine processes which impact health later in life.

STUDY DESIGN SIZE DURATION

A Nordic register-based cohort study was carried out, including all children born in Denmark (birth years 1994-2014), Finland (1990-2014), and Norway (1984-2015). The study included 76 184 liveborn singletons born after ART and 4 403 419 born without ART. Median follow-up was 8.3 and 13.7 years in the ART and non-ART group, respectively.

PARTICIPANTS/MATERIALS SETTING METHODS

The cohort, initiated by the Committee of Nordic Assisted Reproductive Technology and Safety (CoNARTaS), was established by linking national registry data from the medical birth registries and national patient registries available in the Nordic countries. We performed multivariable logistic regression analyses for the birth year intervals 1984-1990, 1991-1995, 1996-2000, 2001-2005, 2006-2010, and 2011-2015, while adjusting for year of birth within each interval, sex of the child, parity, maternal age, maternal diabetes, and maternal smoking during pregnancy as potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

During follow-up, 259 (3.4‰) children born after ART were diagnosed with DM1, while this was the case for 22 209 (5.0‰) born without ART, corresponding to an adjusted odds ratio of 0.98 (95% CI: 0.861.11). Within the different birth year intervals, no significant difference in risk of DM1 between the two groups was found, except for the youngest cohort of children born 2011-2015 where ART was associated with a higher risk of DM1. We found no significant differences in risk of DM1 when comparing children born after IVF versus ICSI or fresh versus frozen embryo transfer, but with only few cases in each group.

LIMITATIONS REASONS FOR CAUTION

The main limitation of the study is the relatively short follow-up time. The incidence rate of DM1 peaks during ages 10-14 years, hence a longer follow-up would benefit all analyses and, in particular, the subgroup analyses.

WIDER IMPLICATIONS OF THE FINDINGS

Overall, our findings are reassuring especially considering the concomitantly increasing number of children born from ART and the increasing incidence of DM1 globally.

STUDY FUNDING/COMPETING INTERESTS

This Nordic registry study has been supported by the Nordic Trial Alliance/NORDFORSK and Rigshospitalets Research Foundation. The funding sources had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. None of the authors has any conflicts of interest to declare regarding this study.

TRIAL REGISTRATION NUMBER

ISRCTN11780826.

Comparison of the performances of survival analysis regression models for analysis of conception modes and risk of type-1 diabetes among 1985-2015 Swedish birth cohort

The goal is to examine the risk of conception mode-type-1 diabetes using different survival analysis modelling approaches and examine if there are differentials in the risk of type-1 diabetes between children from fresh and frozen-thawed embryo transfers. We aimed to compare the performances and fitness of different survival analysis regression models with the Cox proportional hazard (CPH) model used in an earlier study. The effect of conception modes and other prognostic factors on type-1 diabetes among children conceived either spontaneously or by assisted reproductive technology (ART) and its sub-groups was modelled in the earlier study. We used the information on all singleton children from the Swedish Medical Birth Register hosted by the Swedish National Board of Health and Welfare, 1985 to 2015. The main explanatory variable was the mode of conception. We applied the CPH, parametric and flexible parametric survival regression (FPSR) models to the data at 5% significance level. Loglikelihood, Akaike and Bayesian information criteria were used to assess model fit. Among the 3,138,540 singletons, 47,938 (1.5%) were conceived through ART (11,211 frozen-thawed transfer and 36,727 fresh embryo transfer). In total, 18,118 (0.58%) of the children had type-1 diabetes, higher among (0.58%) those conceived spontaneously than the ART-conceived (0.42%). The median (Interquartile range (IQR)) age at onset of type-1 diabetes among spontaneously conceived children was 10 (14-6) years, 8(5-12) for ART, 6 (4-10) years for frozen-thawed embryo transfer and 9 (5-12) years for fresh embryo transfer. The estimates from the CPH, FPSR and parametric PH models are similar. There was no significant difference in the risk of type-1 diabetes among ART- and spontaneously conceived children; FPSR: (adjusted Hazard Ratio (aHR) = 1.070; 95% Confidence Interval (CI):0.929-1.232, p = 0.346) vs CPH: (aHR = 1.068; 95%CI: 0.927-1.230, p = 0.361). A sub-analysis showed that the adjusted hazard of type-1 diabetes was 37% (aHR = 1.368; 95%CI: 1.013-1.847, p = 0.041) higher among children from frozen-thawed embryo transfer than among children from spontaneous conception. The hazard of type-1 diabetes was higher among children whose mothers do not smoke (aHR = 1.296; 95%CI:1.240-1.354, p<0.001) and of diabetic mothers (aHR = 6.419; 95%CI:5.852-7.041, p<0.001) and fathers (aHR = 8.808; 95%CI:8.221-9.437, p<0.001). The estimates from the CPH, parametric models and the FPSR model were close. This is an indication that the models performed similarly and any of them can be used to model the data. We couldn't establish that ART increases the risk of type-1 diabetes except when it is subdivided into its two subtypes. There is evidence of a greater risk of type-1 diabetes when conception is through frozen-thawed transfer.

Type 1 diabetes in children born after assisted reproductive technology: a register-based national cohort study

STUDY QUESTION

Do children born after assisted reproductive technology (ART) have an increased risk of developing type 1 diabetes?

SUMMARY ANSWER

Children born after ART were found to have an increased risk of type 1 diabetes in the unadjusted analysis, while after adjustment this association was only significant in children born after frozen embryo transfer.

WHAT IS KNOWN ALREADY?

Some studies raise concerns as to whether fertility treatments may influence long-term morbidity in children born after ART. Elevated blood pressure and altered glucose metabolism have been found after ART in a few studies.

STUDY DESIGN, SIZE, DURATION

A register-based national cohort study that included all children born in Sweden between 1985 and 2015-in total, 3 138 540 children-was carried out.

PARTICIPANTS/MATERIAL, SETTING, METHODS

The study was population-based and all live-born singleton children born after ART (n = 47 938) or spontaneous conception (SC) (n = 3 090 602) were included. The ART cohort comprised 36 727 children born after fresh embryo transfer and 11 211 children born after frozen embryo transfer. Several national registries were used together with data from Statistics Sweden.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 202 children born after ART and 17 916 children born after SC developed type 1 diabetes, corresponding to 43.4 and 35.5 per 100 000 person-years at risk (hazard ratio [HR] 1.23; 95% confidence interval [CI], 1.07 to 1.42). Mean follow-up was 9.7 (SD 6.4) years for ART children and 16.3 (SD 9.2) years for SC children. After adjustment for calendar year of birth, HR for type 1 diabetes was 1.13; 95% CI, 0.98-1.30. After further adjustment for sex, maternal age, country of birth, educational level, smoking and parental diabetes, HR was 1.07; 95% CI, 0.93-1.23. In subgroup analyses, an association was found between frozen embryo transfer and type 1 diabetes (adjusted HR 1.52; 95% CI, 1.08-2.14 and 1.41; 95% CI, 1.05-1.89 for frozen versus fresh and frozen versus SC, respectively). When comparing intracytoplasmic sperm injection to in vitro fertilization, no difference was found (adjusted HR 1.08; 95% CI, 0.77-1.51).

LIMITATIONS, REASONS FOR CAUTION

Limitations were the missing data and residual confounding caused by unknown confounders. Furthermore, the control group consisted of all children not conceived by ART and not non-ART children from subfertile mothers. The study was also performed in only singletons and not in the total ART population.

WIDER IMPLICATIONS OF THE FINDINGS

Type 1 diabetes is a serious disease, affecting human life in several ways, including risk of serious complications, reduced life span and a life-long treatment. Our results are generally reassuring, showing no increase in diabetes in ART children compared to children born after SC after adjustment for relevant confounders. The observation of an association between children born after frozen embryo transfer and type 1 diabetes, although based on subgroup analyses with a limited number of children and modest in size, is however a reason for concern.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by Nordforsk 71450, the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement 70940, and the Hjalmar Svensson Foundation. The authors have no competing interests.

TRIAL REGISTRATION NUMBER

ISRCTN 11780826.

The Danish National Register of assisted reproductive technology: content and research potentials

The Danish National Register of assisted reproductive technology (ART) was initially established in 1994. The register comprises complete information on all ART procedures in public and private clinics in Denmark from 2013 and onwards, including baseline information on the cause of infertility and a number of health-related patient characteristics. The register enables monitoring and research on infertility treatment and reproductive topics in single women or couples seeking assisted reproduction, and the register is thus a key component of the Danish health information system within human reproduction. We aimed to provide an updated description of the register including advantages and pitfalls when using the register for reproductive epidemiological research, and a description of the accessibility for researchers. The Danish ART register is a valuable tool for epidemiological research. However, the inherent strengths and limitations ought to be in perspective when designing studies and interpreting the study results. Reports with annually aggregated data on ART treatments, can be accessed on the Danish Health Data Authority web page and researchers may obtain access to individual pseudonomized data via secure servers at the Danish Health Data Authority and Statistics Denmark.

Increased risk of metabolic dysfunction in children conceived by assisted reproductive technology

AIMS/HYPOTHESIS

Assisted reproductive technology (ART) is the most widely used treatment for infertility and has resulted in millions of births worldwide. The safety of the offspring has been of the utmost concern. Previous studies suggested an increase in metabolic disorders in offspring later in life. The aim of the present study was to investigate metabolic changes at age 6-10 years in offspring conceived as a result of in vitro fertilisation/intracytoplasmic sperm injection (IVF/ICSI).

METHODS

A total of 380 children born from IVF/ICSI and a matched control group of 380 naturally conceived children, all aged 6-10 years, were recruited. Anthropometric measures, ultrasound and serum tests were performed for body mass, glucose metabolism and lipid profiles, and examination of vasculature structure.

RESULTS

The children conceived by ART showed significantly higher fasting blood glucose and serum insulin levels and HOMA-IR (adjusted β [95% CI]: fasting blood glucose 0.49 [0.42, 0.55]; log_e-transformed insulin 0.28 [0.20, 0.35]; log_e-transformed HOMA-IR 0.38 [0.30, 0.46]), as well as a lower HOMA-B and serum apolipoprotein A (ApoA) levels (adjusted β [95% CI]: log_e-transformed HOMA-B -0.19 [-0.27, -0.11]; ApoA -0.17 [-0.21, -0.13]), when compared with the control group. Furthermore, the ultrasound scan indicated elevated carotid intima-media thickness in children conceived by ART (β 0.13 [95% CI 0.12, 0.13]).

CONCLUSIONS/INTERPRETATION

Children conceived by IVF/ICSI have a less favourable glucose and cardiovascular metabolic profile in childhood when compared with naturally conceived children. The underlying mechanisms and potential long-term consequences need to be elucidated in future studies. Graphical abstract.

The Challenges of Identifying Environmental Determinants of Type 1 Diabetes: In Search of the Holy Grail

Type 1 diabetes is the result of autoimmune-mediated destruction and inflammation of the insulin-producing β-cells of the pancreas. The excess morbidity and mortality from its complications coupled with its increasing incidence emphasize the importance to better understand the etiology of this condition. It has a strong genetic component, but a genetic predisposition is not the sole contributor to disease development as only 30% to 50% of identical twins both develop the disease. In addition, there are multiple lines of evidence to support that environmental factors contribute to the pathogenesis of type 1 diabetes. Environmental risk factors that have been proposed include infections, dietary factors, air pollution, vaccines, location of residence, childhood obesity, family environment and stress. Researchers have conducted many observational studies to identify and characterize these potential environmental factors, but findings have been inconsistent or inconclusive. Many studies have had inherent methodological issues in recruitment, participation, defining cases and exposures, and/or data analysis which may limit the interpretability of findings. Identifying and addressing these limitations may allow for greatly needed advances in our understanding of type 1 diabetes. As such, the purpose of this article is to review and discuss the limitations of observational studies that aim to determine environmental risk factors for type 1 diabetes and propose recommendations to overcome them.

Risk of juvenile idiopathic arthritis among children conceived after fertility treatment: a nationwide registry-based cohort study

STUDY QUESTION

Is the risk of juvenile idiopathic arthritis (JIA) increased in children conceived after fertility treatment, and is an observed association caused by specific types of fertility treatment or by factors associated with the underlying infertility?

SUMMARY ANSWER

The risk of JIA in children conceived after fertility treatment (any and specific types of fertility treatment) was not convincingly affected when compared with children born to fertile women.

WHAT IS KNOWN ALREADY

It has been suggested that fertility treatment may affect the development of the immune system and thereby increase the risk of developing autoimmune diseases, including JIA.

STUDY DESIGN, SIZE, DURATION

This retrospective population-based cohort study included all live-born children in Denmark between 1 January 1996 and 31 December 2012 (n = 1 084 184). The study population was followed from date of birth until first diagnosis of JIA as registered in the Danish National Patient Registry, date of 16th birthday, date of emigration, date of death or end of follow-up (31 December 2014), whichever occurred first.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study cohort was linked to the Danish Infertility Cohort in order to identify children born to women with fertility problems (n = 174 702) and fertility treatment (n = 89 931). Cox proportional hazard regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

During a median follow-up period of 10.3 years, 2237 children were diagnosed with JIA. Children born to women with fertility problems had an increased risk of JIA (HR 1.18, 95% CI 1.05-1.32) compared with children born to fertile women. However, the risk was not increased in children conceived after any fertility treatment (HR 1.11; 95% CI 0.95-1.29), or after specific types of fertility treatment being ART (HR 1.05; 95% CI 0.83-1.33), IVF (HR 1.01; 95% CI 0.73-1.38), ICSI (HR 0.98; 95% CI 0.64-1.50) or any fertility drugs (HR 1.10; 95% CI 0.94-1.28) compared with children born to fertile women. The associations between fertility treatment and JIA were also assessed by using children born to women with fertility problems without fertility treatment in the index pregnancy as a reference group, however, the findings did not change substantially.

LIMITATIONS REASONS FOR CAUTION

Despite a large study population, the statistical precision in some subgroup analyses may be affected due to the low number of JIA cases. There may be some misclassification of fertility problems, as some women have undiagnosed fertility problems and are therefore not included in the Danish Infertility Cohort; potentially leading to slight attenuation of the association between fertility problems and JIA.

WIDER IMPLICATIONS OF THE FINDINGS

The results are based on national data and our findings can therefore be applied to other similar populations. Our results indicate that fertility treatment per se do not increase the risk of JIA but merely that the increased risk of JIA observed among children born to women with fertility problems may be due to underlying factors related to both infertility and JIA. However, as this is the first large study in this field, further studies are needed to confirm our findings.

STUDY FUNDING/COMPETING INTEREST(S)

The study was supported by grants from the Jascha Foundation, the Aase and Ejner Danielsens Foundation and The Danish Rheumatism Association. All authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.