Risk of borderline ovarian tumors after fertility treatment - Results from a Danish cohort of infertile women

OBJECTIVE

Results from previous studies examining the association between fertility treatment and borderline ovarian tumors are inconsistent. The aim of this study was to investigate the association between fertility treatment and borderline ovarian tumors in a cohort of infertile women.

METHODS

This cohort study was based on the Danish Infertility Cohort and included all infertile women aged 20-45 years living in Denmark between 1 January 1995 and 31 December 2017 (n = 146,891). Information on use of fertility drugs, borderline ovarian tumors and cancer diagnoses, covariates, emigration, and vital status was obtained by linkage to national registers. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) with adjustment for potential confounders for overall borderline ovarian tumors and for serous- and mucinous borderline ovarian tumors separately.

RESULTS

During a median 11.3 years of follow-up, 144 women developed a borderline ovarian tumor. No marked associations between ever use of clomiphene citrate, gonadotropins, gonadotropin-releasing hormone receptor modulators, human chorionic gonadotropin or progesterone and borderline ovarian tumors were observed, neither overall nor for serous and mucinous borderline ovarian tumors analysed separately. Further, no clear associations with borderline ovarian tumors were found according to cumulative dose, time since first use or parity status for any fertility drugs.

CONCLUSIONS

No marked associations between use of fertility drugs and borderline ovarian tumors were observed. However, the cohort's relatively young age at end of follow-up emphasizes the importance of extending the follow-up period for women who have used fertility drugs.

Maternal use of hormonal contraception and risk of childhood autism spectrum disorders: A Parental Exposures and Child Health (PECH) cohort study

A recent hypothesis suggests that maternal hormonal contraception use has contributed to the increasing incidence of autism spectrum disorders (ASD). We used a nationwide population-based cohort (the PECH cohort) including 1,056,149 Danish children born in the period January 1, 1998, to December 31, 2014, to assess associations between maternal hormonal contraception use and childhood ASD (end of follow-up: December 31, 2017). Maternal hormonal contraception use was grouped as "recent use" (≤ 3 months before pregnancy start or during pregnancy), "previous use" (>3 months before pregnancy start) and "never use", except for few products. Incidence rate ratios (IRRs) were estimated using Poisson regression. During follow-up of nearly 12 million person-years, 19,996 children were diagnosed with ASD. A slightly higher IRR was observed for maternal recent use of any hormonal contraception, compared to previous use. This association was largely driven by the non-oral progestin-only products, and associations were especially seen for infantile autism and other/unspecified ASD. An increased IRR of infantile autism was also observed for recent use of the oral progestin-only products, compared to previous use. Our results suggest that maternal use of hormonal contraception may be associated with ASD risk in children, especially for the progestin-only products.

In Utero Exposure to Hormonal Contraception and Mortality in Offspring with and without Cancer: A Nationwide Cohort Study

Approximately 400 million women of reproductive age use hormonal contraceptives worldwide. Eventually, pregnancy sometimes occurs due to irregular use. Use in early pregnancy is found to be associated with child morbidities including cancer, the main reason for disease-related death in children. Here, we add the missing piece about in utero exposure to hormonal contraception and mortality in offspring, including assessments of prognosis in children with cancer. In utero exposure to hormonal contraception may be associated with death since we found a hazard ratio (HR) of 1.22 (95% confidence interval (CI) 1.01-1.48) compared to children of mothers with previous use. The HRs were 1.22 (95% CI 0.99-1.13) for oral combined products and 2.92 (95% CI 1.21-7.04) for non-oral progestin-only products. A poorer prognosis was also found in exposed children with leukemia (3.62 (95% CI: 1.33-9.87)). If causal, hormonal contraception in pregnancy seems detrimental for offspring health and a marker of poorer prognosis in children with leukemia.

Effects of early maternal cancer and fertility treatment on the risk of adverse birth outcomes

BACKGROUND

Early maternal cancer and fertility treatment each increase the risk for adverse birth outcomes, but the joint effect of these outcomes has not yet been reported. Thus, the aim was to assess the individual and joint effect of maternal cancer and fertility treatment on the risk for adverse birth outcomes.

METHODS

This population-based cohort study included 5487 live-born singletons identified in the Danish Medical Birth Register (1994-2016) of mothers with previous cancer (<40 years) recorded in the Danish Cancer Registry (1955-2014). We randomly selected 80,262 live-born singletons of mothers with no cancer <40 years matched to mothers with cancer by birth year and month. We calculated odds ratios (ORs) for preterm birth, low birth weight (LBW) (<2500 g) and small for gestational age (SGA), mean differences in birth weight in grams, and additional cases of preterm birth (gestational age<259 days) per 100,000 person-years. Multiplicative and additive interaction of maternal cancer and fertility treatment was compared with outcomes of children conceived naturally to mothers with no maternal cancer (reference group).

FINDINGS

Among 84,332 live-born singletons, increased ORs for preterm birth were observed among children born to mothers with previous cancer (1·48, 95% confidence interval [CI] 1·33-1.65) or after fertility treatment (1·43, 95% 1·28-1-61), with 22 additional cases of preterm birth among both group of children (95% CI 15-29; 95% CI 14-30). In the joint analyses, the OR for SGA for children born after fertility treatment to mothers with previous cancer was similar to that of the reference group (OR 1·02, 95% CI 0·72-1·44, P for interaction=0·52). Children with both exposures had increased ORs for LBW (1·86, 95% CI 1·17-2·96, P for interaction=0·06) and preterm birth (2·31, 955 CI 1·66-3·20, P for interaction = 0·56), with 61 additional cases of preterm birth (95% CI 27-95, P for interaction=0.26) over that of children in the reference group. The mean birth weight was also lower in children born to mothers with both exposures (-140 g, 95% CI -215; -65) (P for interaction=0.06) but decreased to -22 g (95% CI -76; 31) after adjustment for GA.

INTERPRETATION

Although we did not find any statistically significant additive interaction between maternal cancer and fertility treatment, children born after fertility treatment of mothers with previous cancer were at increased risk for adverse birth outcomes. Thus, pregnant women with both exposures need close follow-up during pregnancy.

FUNDING

The Danish Cancer Society and the Danish Childhood Cancer Foundation.

Association Between Maternal Hormonal Contraception Use and Central Nervous System Tumors in Children

IMPORTANCE

The incidence of central nervous system (CNS) tumors in children appears to be increasing, yet few risk factors are established. There is limited information regarding whether maternal hormonal contraception use increases this risk.

OBJECTIVE

To examine the association between maternal hormonal contraception use and CNS tumors in children (<20 years).

DESIGN, SETTING, AND PARTICIPANTS

In this nationwide cohort study based on population-based registry data, 1 185 063 children born in Denmark between January 1, 1996, and December 31, 2014, were followed up for a diagnosis of a CNS tumor (final follow-up on December 31, 2018).

EXPOSURES

Maternal hormonal contraception use was analyzed according to any use, regimen (combined/progestin only), and route of administration (oral/nonoral), categorized as recent use (≤3 months before start and during pregnancy), previous use (>3 months before start of pregnancy), and no use. For injections, implants, and intrauterine devices that are used for a different time period, the categorization was appropriately altered.

MAIN OUTCOMES AND MEASURES

Hazard ratio (HR) and incidence rate difference (IRD) of CNS tumors diagnosed at younger than 20 years.

RESULTS

After 15 335 990 person-years of follow-up (mean follow-up, 12.9 years), 725 children were diagnosed with a CNS tumor. The mean age at diagnosis was 7 years, and 342 (47.2%) of the diagnosed children were female. The adjusted incidence rate of CNS tumors per 100 000 person-years was 5.0 for children born to mothers with recent hormonal contraception use (n = 136 022), 4.5 for children born to mothers with previous use (n = 778 843), and 5.3 for children born to mothers with no use (n = 270 198). The corresponding HRs were 0.95 ([95% CI, 0.74-1.23]; 84 children with CNS tumors; IRD, -0.3 [95% CI, -1.6 to 1.0]) for recent use and 0.86 ([95% CI, 0.72-1.02]; 421 children with CNS tumors; IRD, -0.8 [95% CI, -1.7 to 0.0]) for previous use, compared with no use. No statistically significant associations were found for recent or previous use of oral combined, nonoral combined, oral progestin only, or nonoral products compared with no use of hormonal contraception.

CONCLUSIONS AND RELEVANCE

Among Danish children, there was no statistically significant association between any maternal hormonal contraception use and CNS tumor risk.

Maternal Medication Use and Childhood Cancer in Offspring-Systematic Review and Considerations for Researchers

Cancer is an important cause of childhood mortality, yet the etiology is largely unknown. A combination of pre- and postnatal factors is thought to be implicated, including maternal medication use. We aimed to provide: 1) a systematic review of peer-reviewed publications on associations between maternal medication use and childhood cancer, with a focus on study design and methodology; and 2) suggestions for how to increase transparency, limit potential biases, and improve comparability in studies on maternal medication use and childhood cancer. We conducted a systematic search in the PubMed, Embase, Scopus, Cochrane, and Web of Science databases to June 8, 2020. Altogether, 112 studies were identified. The reviewed studies were heterogeneous in study design, exposure, and outcome classification. In 21 studies (19%), the outcome was any childhood cancer. Of the 91 papers that reported on specific types of cancer, 62% did not report the cancer classification system. The most frequently investigated medication groups were sex hormones (46 studies, excluding fertility medications), and antiinfectives (37 studies). Suggestions for strengthening future pharmacoepidemiologic studies on maternal medication use and childhood cancer relate to choice of cancer classification system, exposure windows, and methods for identification of, and control for, potential confounders.

Prenatal exposure to nitrofurantoin and risk of childhood leukaemia: a registry-based cohort study in four Nordic countries

Background

Studies have suggested increased risks of childhood leukaemia after prenatal exposure to antibiotics, particularly nitrofurantoin. However, these findings may be related to the underlying maternal infection. This multinational study aimed to investigate the association between prenatal nitrofurantoin exposure and childhood leukaemia while accounting for maternal infection.

Methods

In a population-based cohort study of children born in Denmark, Finland, Norway or Sweden from 1997 to 2013, prenatal exposure to nitrofurantoin or pivmecillinam (active comparator) was ascertained from national Prescription Registries. Childhood leukaemia was identified by linkage to national Cancer Registries. Poisson regression was used to estimate incidence rate ratios (IRRs) and incidence rate differences (IRDs) with inverse probability of treatment weights applied to account for confounding.

Results

We included 44 091 children prenatally exposed to nitrofurantoin and 247 306 children prenatally exposed to pivmecillinam. The children were followed for 9.3 years on average (standard deviation 4.1). There were 161 cases of childhood leukaemia. The weighted IRR for prenatal nitrofurantoin exposure when compared with pivmecillinam was 1.34 (95% confidence interval 0.88, 2.06), corresponding to an IRD of 15 per million person-years. Higher point estimates were seen for first- and third-trimester exposure. There was no evidence of a dose–response relationship.

Conclusions

Prenatal exposure to nitrofurantoin was not substantially associated with childhood leukaemia, although a slightly elevated IRR with confidence intervals including the null was observed, corresponding to a small absolute risk. The lack of a dose–response relationship and a clear biological mechanism to explain the findings suggests against a causal association.

Maternal use of hormonal contraception and epilepsy in offspring

STUDY QUESTION

Is maternal use of hormonal contraception associated with the development of epilepsy in the offspring?

SUMMARY ANSWER

We found that maternal use of hormonal contraception was associated with a slightly increased risk of epilepsy in the offspring.

WHAT IS KNOWN ALREADY

Foetal exposure to exogenous hormones has been associated with changes in brain development. However, little is known about maternal hormonal contraception use and development of epilepsy in the offspring.

STUDY DESIGN, SIZE, DURATION

A nationwide cohort of all live born children born in Denmark between 1 January 1998 and 31 December 2014, was followed from day 29 after birth for epilepsy (first diagnosis of epilepsy or first redeemed prescription for anti-epileptic medication) to censoring (emigration, death) or 31 December 2015, whichever occurred first.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Diagnoses of epilepsy were obtained from the National Patient Registry. The Danish National Prescription Registry supplied information on redeemed prescriptions for hormonal contraception and anti-epileptic medication. Maternal hormonal contraception use was categorized as never use (reference group), previous use (prescriptions redeemed >3 months before pregnancy start) and recent use (prescriptions redeemed ≤3 months before or during pregnancy).

MAIN RESULTS AND THE ROLE OF CHANCE

The data show that 17 585 children developed epilepsy during a median follow-up of 9.2 years (9 732 635 person-years). The hazard ratio (HR) for epilepsy was 1.07 (95% CI 1.02-1.13) in children of mothers who had used any type of hormonal contraception recently, compared with children of mothers who had not used hormonal contraception. The HR was similar for recent use of oral combined products, while the HRs for recent or previous use of non-oral combined products were 1.32 (95% CI 0.98-1.77) and 1.16 (95% CI 1.02-1.32), respectively. For non-oral progestin-only products, the HRs were 1.19 (95% CI 1.04-1.38) and 1.53 (95% CI 1.31-1.80), respectively, for recent and previous use.

LIMITATIONS, REASONS FOR CAUTION

There may be some misclassification of maternal hormonal contraception use, as some women may not have used the redeemed prescriptions or used them at a different point in time; potentially leading to an attenuation of the estimates. In addition, although we were able to account for known risk factors for epilepsy, unknown or residual confounding cannot be ruled out.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings are based on nationwide population-based data and can therefore be applied to other similar populations. However, as this is the first study in this field, further studies are needed to confirm our findings.

STUDY FUNDING/COMPETING INTEREST(S)

No specific funding was obtained for this study, which was supported by internal funding at the Unit of Virus, Lifestyle and Genes. All authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Hospital Contacts for Psychiatric Disorders in Parents of Children With Cancer in Denmark

Background

Having a child diagnosed with cancer is a devastating experience that may affect parents' mental health. We aimed to assess the risk of hospital contacts for psychiatric disorders in parents of children with cancer.

Methods

We conducted a nationwide population-based cohort study using Danish registry data. Parents of children diagnosed with cancer between 1982 and 2014 (n = 6689 mothers, n = 5509 fathers) were matched with comparison parents of cancer-free children (n = 67 544 mothers, n = 55 756 fathers). We used Cox proportional hazards models to estimate the risk of hospital contacts for any psychiatric disorder and specific disorders. Cox models were also used to investigate sociodemographic and cancer-related risk factors for psychiatric disorders.

Results

Incidence rates of hospital contacts for any psychiatric disorder were 426 per 100 000 person-years in mothers of children with cancer and 345 per 100 000 person-years in comparison mothers. For fathers, the respective incidence rates were 260 and 262 cases per 100 000 person-years. Compared with parents of cancer-free children, mothers of children with cancer were at an increased risk of hospital contacts for any psychiatric disorder (hazard ratio = 1.23, 95% confidence interval = 1.12 to 1.36), whereas no elevated risk was seen in fathers (hazard ratio = 0.99, 95% confidence interval = 0.87 to 1.13). Among mothers, risks were particularly elevated for affective and stress-related disorders. Parents of deceased children and children diagnosed at a younger age were at particular risk of hospital contacts for psychiatric disorders.

Conclusion

Hospital contacts for psychiatric disorders were overall rare. Health-care professionals should draw attention to subgroups of vulnerable parents to meet their needs of support and adequate treatment.

Ninth-grade school achievement in Danish children conceived following fertility treatment: a population-based cohort study

OBJECTIVE

To assess whether academic achievement among children conceived following fertility treatment is different from that of children born to fertile women while also considering the underlying infertility.

DESIGN

Population-based cohort study.

SETTING

Denmark.

PATIENT(S)

The study population consisted of all 154,536 firstborn, live-born, singleton children in Denmark between 1995 and 2000 who completed their ninth grade with an examination.

INTERVENTION(S)

The Danish Infertility Cohort was used to identify children conceived after fertility treatment (n = 10,099), and information on mean school marks was obtained from Statistics Denmark.

MAIN OUTCOME MEASURE(S)

Linear regression models were used to estimate mean differences (MDs) and 95% confidence intervals (CIs). Multiple logistic regression models were used to estimate odds ratios (OR) and 95% CI of not passing the ninth-grade examination.

RESULTS

The crude overall mean marks for children conceived after the various fertility treatment procedures were in general higher than in children born to fertile women. However, after adjustment for potential confounders, the overall mean marks were statistically significantly lower for children conceived after the various fertility treatment procedures (e.g., any fertility treatment: MD -0.13; 95% CI -0.18, -0.08) compared with children born to fertile women. Further, children conceived after any fertility treatment had a statistically significant lower crude likelihood of not passing the ninth-grade examination (OR 0.66; 95% CI 0.53, 0.81) compared with children born to fertile women, whereas no difference was observed in the confounder adjusted analyses (OR 1.15; 95% CI 0.89, 1.49). When children born to women requiring fertility assistance but without fertility treatment in the index pregnancy were used as a reference group, no differences in the adjusted overall mean marks and the likelihood of not passing the ninth grade with an examination were observed.

CONCLUSION

Our findings indicate that fertility treatment per se is not associated with lower school marks and the likelihood of not passing the ninth grade with an examination. Hence, we suggest that factors related to both fertility problems and cognitive development may more likely explain the slightly lower academic performance (i.e., modest lower mean marks) among children conceived after fertility treatment.

Maternal use of hormonal contraception and risk of childhood ADHD: a nationwide population-based cohort study

Although maternal use of hormones has been suspected of increasing the risk for childhood attention-deficit/hyperactivity disorder (ADHD), no study has examined hormonal contraception use in this context. We examined the association between maternal hormonal contraception use before or during pregnancy and ADHD risk in children. This nationwide population-based cohort study included 1,056,846 children born in Denmark between 1998 and 2014. Prescriptions for hormonal contraceptives redeemed by the mother was categorized as: no use, previous use (> 3 months before pregnancy), and recent use (≤ 3 months before or during pregnancy). Children were followed for ADHD, from birth until 31 December 2015. Cox proportional hazard models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs). During 9,819,565 person-years of follow-up (median: 9.2), ADHD was diagnosed or a prescription for ADHD medication redeemed for 23,380 children (2.2%). The adjusted HR for ADHD was higher in children of mothers who had previously (HR 1.23; 95% CI 1.18-1.28) or recently (HR 1.30; 95% CI 1.24-1.37) used hormonal contraception than in those of mothers with no use. The highest estimates were seen for use of non-oral progestin products with HRs of 1.90 (95% CI 1.59-2.26) for previous use, 2.23 (95% CI 1.96-2.54) for recent use, and 3.10 (95% CI 1.62-5.91) for use during pregnancy. Maternal use of hormonal contraception was associated with an increased risk for ADHD in the offspring; more pronounced for non-oral progestin-only than other products.

The impact of childhood cancer on parental separation, divorce, and family planning in Denmark

BACKGROUND

Childhood cancer is a devastating experience for the family. The objective of the current study was to assess the impact of having a child with cancer on parental separation, divorce, and future family planning among families residing in Denmark.

METHODS

The authors conducted a nationwide cohort study using Danish registry data. Parents of children diagnosed with cancer between 1982 and 2014 (7066 children and 12,418 case parents) were matched with 10 comparison parents of cancer-free children per case parent (69,993 children and 125,014 comparison parents). We used discrete-time Cox regression models to compare the risk of separation (end of cohabitation) and divorce between case and comparison parents, and to identify risk factors for separation and divorce among case parents only. Descriptive statistics were used to compare family planning between case and comparison parents.

RESULTS

Case parents were found to have a slightly lower risk of separation (hazard ratio, 0.96; 95% confidence interval, 0.93-0.99) and divorce (hazard ratio, 0.92; 95% confidence interval, 0.87-0.97) than comparison parents. The authors found that case parents who were aged <45 years, with short education (an International Standard Classification of Education code indicating early childhood education, primary education, and lower secondary education), and who were unemployed were at an increased risk of separation and divorce. Moreover, the parents of children diagnosed with cancer at a young age (aged <15 years) were more likely to separate or divorce. No differences with regard to the total number of children and time to a next child after the cancer diagnosis were observed between case and comparison parents.

CONCLUSIONS

Having a child with cancer was not associated with an overall adverse impact on parents' risk of separation or divorce and future family planning. These encouraging findings should be communicated to parents to support them along their child's cancer trajectory.

Incidence and time trends of childhood cancer in Denmark, 1943-2014

Background: Surveillance of childhood cancer incidence is informative for etiologic research and health policy. However, high-quality data covering several decades of virtually complete cancer diagnosis in children is sparse.Methods: Incident cases of childhood cancer (0-19 years at diagnosis), classified according to Birch and Marsden's International Classification of Childhood Cancer, first edition (ICCC-1), were identified in the Danish Cancer Registry and used to calculate age-standardized incidence rates (ASRs) and estimated annual percentage change (EAPC) separately for 1943-1977 (early period) and 1977-2014 (recent period).Results: During 1943-2014, 15,184 childhood cancer cases were reported. The ASR for any cancer was 13.0 per 100 000 person-years in the early period (EAPC 0.55%; 95% CI 0.30-0.80) and 17.7 per 100 000 person-years in the recent period (EAPC 1.16%; 95% CI 0.96-1.36). In both periods, the increasing trend was seen in both boys (EAPC 0.69%; 95% CI 0.43-0.96/EAPC 0.96%; 95% CI 0.75-1.17) and girls (EAPC 0.37%; 95% CI -0.01-0.75/EAPC 1.41%; 95% CI 1.11-1.72) and in children aged 0-14 years (EAPC 0.53%; 95% CI 0.26-0.80/EAPC 0.86%; 95% CI 0.64-1.08) and 15-19 years (EAPC 0.60%; 95% CI 0.19-1.02/EAPC 1.97%; 95% CI 1.67-2.28). Increasing trends were observed for all main diagnostic groups.Conclusions: The incidence of childhood cancer in Denmark has increased since the 1940s, especially since 1977 and in older children. In recent years the increase has been most pronounced among girls.

Risk of febrile seizures among children conceived following fertility treatment: A cohort study

BACKGROUND

Studies have shown that fertility treatment in mothers is associated with neurological problems in children. However, knowledge about any association between maternal use of fertility treatment and febrile seizures in children is lacking.

OBJECTIVE

To determine whether maternal use of fertility treatment is associated with febrile seizures in children.

METHODS

All liveborn children in Denmark during 1996-2012 (n = 1 065 901) were linked with the Danish Infertility Cohort and the Danish national registers and were followed from one year of age until the first episode of a febrile seizure, death, emigration, loss to follow-up, or end of follow-up (December 2015). Cox proportional hazard regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with adjustment for potential confounders.

RESULTS

Approximately 16% children (n = 172 140) were conceived by infertile women, and approximately 3% (n = 34 082) were diagnosed with febrile seizures during follow-up. Compared with children conceived by fertile women, children conceived following any fertility treatment (HR 1.11, 95% CI 1.06, 1.16), following specific fertility treatment, for example IVF (HR 1.15, 95% CI 1.05, 1.25), ICSI (HR 1.20, 95% CI 1.10, 1.32), and following fertility drugs (HR 1.06, 95% CI 1.00, 1.11) had slight increase in risk of febrile seizures, after adjusting for calendar year of birth, parental age, education, parity status, and maternal smoking during pregnancy. The associations were unchanged when children conceived naturally by infertile women were used as the reference group.

CONCLUSIONS

Children conceived following fertility treatment had slightly increased relative risk for febrile seizures.

Association Between Fertility Treatment and Cancer Risk in Children

IMPORTANCE

An increasing number of children worldwide are born after the use of fertility treatment, although it remains unclear whether the treatment affects the risk of childhood cancer and whether any associations observed are due to the use of specific drugs, the use of specific procedures, or the underlying infertility.

OBJECTIVE

To examine the association between different types of fertility treatments and cancer risk in children.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study based on Danish population-based registry data and the Danish Infertility Cohort (individual record linkage) that included 1 085 172 children born in Denmark between January 1, 1996, and December 31, 2012, linked with parental information. There were a total of 2217 children diagnosed with cancer (follow-up occurred during 1996-2015).

EXPOSURES

Maternal fertility treatment during the index pregnancy, including the use of fertility drugs (clomiphene [n = 33 835], gonadotropins [n = 57 136], gonadotropin-releasing hormone analogs [n = 38 653], human chorionic gonadotropin [n = 68 181], progesterone [n = 41 628], and estrogen [n = 16 948]) and assisted reproductive technology (in vitro fertilization [n = 19 448], intracytoplasmic sperm injection [n = 13 417], and frozen embryo transfer [n = 3356]). Each exposure was examined separately and compared with children born to fertile women.

MAIN OUTCOMES AND MEASURES

Hazard ratios and incidence rate differences for childhood cancer.

RESULTS

After 12.2 million person-years of follow-up (mean, 11.3 years), the incidence rate of childhood cancer was 17.5 per 100 000 for children born to fertile women (n = 910 291) and 44.4 per 100 000 for children born after the use of frozen embryo transfer (n = 3356). Compared with children born to fertile women, the use of frozen embryo transfer was associated with an elevated risk of childhood cancer (14 cancer cases; hazard ratio, 2.43 [95% CI, 1.44 to 4.11]; incidence rate difference, 26.9 [95% CI, 2.8 to 51.0] per 100 000), mainly due to an increased risk of leukemia (5 cancer cases; incidence rate, 14.4 per 100 000; hazard ratio, 2.87 [95% CI, 1.19 to 6.93]; incidence rate difference, 10.1 [95% CI, -4.0 to 24.2] per 100 000) and sympathetic nervous system tumors (<5 cancer cases; hazard ratio, 7.82 [95% CI, 2.47 to 24.70]). There were no statistically significant associations with the use of the other types of fertility treatment examined.

CONCLUSIONS AND RELEVANCE

Among children born in Denmark, the use of frozen embryo transfer, compared with children born to fertile women, was associated with a small but statistically significant increased risk of childhood cancer; this association was not found for the use of other types of fertility treatment examined.

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.

Childhood vaccinations and risk of acute lymphoblastic leukaemia in children

Background

It has been proposed that childhood vaccinations protect against acute lymphoblastic leukaemia (ALL) in children by modulation of future responses to common infections in childhood. However, the available studies provide inconsistent findings, and population-based cohort studies with longitudinal information on vaccinations are lacking.

Methods

In a register-based cohort of all children born in Denmark from 1 January 1990 to 31 December 2008, followed up until age 15 years or 31 December 2009 ( n  = 1 225 404), we evaluated exposure to childhood vaccination and risk of childhood ALL, including information on ALL subtypes. Using Cox regression, we estimated hazard ratios (HRs) comparing vaccinated with unvaccinated children.

Results

Childhood ALL was diagnosed in 490 children during 10 829 194 person-years of follow-up. Neither the total number of vaccine doses received nor exposure to each vaccination given in childhood was associated with altered risk of ALL, including the following: (i) Haemophilus influenzae type b [HR, 1.04; 95% confidence interval (CI), 0.68-1.61]; ii) measles, mumps and rubella (HR, 1.01; 95% CI, 0.76-1.34); iii) whole-cell pertussis (HR, 1.10; 95% CI, 0.51-2.39); and iv) diphtheria, tetanus and inactivated polio (HR, 1.14; 95% CI, 0.42-3.13). Analyses conducted according to ALL subtypes defined by immunopheno- and karyotypes showed no association with childhood vaccination.

Conclusions

This nationwide cohort study provides no support of the proposed protective effect of childhood vaccination against childhood ALL.

Coffee, tea and caffeine consumption and risk of primary infertility in women: a Danish cohort study

INTRODUCTION

The aim of this study was to investigate whether consumption of coffee, tea and caffeine affects the risk of primary infertility in women.

MATERIAL AND METHODS

We selected nulliparous Danish women aged 20-29 years from a prospective cohort and retrieved information on coffee and tea consumption from a questionnaire and an interview at enrollment. We assessed the women's fertility by linkage to the Danish Infertility Cohort and retrieved information on children and vital status from the Civil Registration System. All 7574 women included for analysis were followed for primary infertility from the date of enrollment (1991-1993) until 31 December 2010. Analyses were performed with Cox proportional hazard models.

RESULTS

During follow up, primary infertility was diagnosed in 822 women. Compared with never consumers, the risk of primary infertility among women who drank coffee or tea was not affected. The risk of primary infertility was neither associated with an increasing number of daily servings of coffee (hazard ratio 1.00; 95% confidence interval (CI), 0.97-1.03) or tea (hazard ratio 1.01; 95% CI, 0.99-1.03) in consumers only. Concerning total caffeine consumption (from coffee and tea), the risk of infertility was similar among consumers compared with never consumers. Finally, none of the additional daily 100 mg of caffeine affected the risk among consumers only (hazard ratio 1.00; 95% CI 0.98-1.02).

CONCLUSIONS

In this population-based cohort study, not restricted to women seeking pregnancy, we found no association between coffee, tea or total caffeine consumption and the risk of primary infertility in women.

Maternal fertility problems and risk for transient neonatal diabetes mellitus

AIMS

The study of imprinting disorders in the context of infertility and its treatment is important, as studies have indicated an increased risk. In this study, we evaluated the risk of transient neonatal diabetes mellitus (TNDM), defined here as diabetes mellitus presenting within the first six weeks of life, in children born to women with fertility problems.

METHODS

This nationwide register-based cohort study comprised all 2,107,837 children born in Denmark between 1977 and 2010. Of these, 121,044 (5.7%) children were born to women with fertility problems. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between maternal fertility status and the risk for TNDM.

RESULTS

A total of 103 children developed TNDM during the follow-up period. Children born to women with fertility problems had an elevated risk for TNDM, after adjustment for birth year, maternal age at birth and parental history of diabetes, although this was not statistically significant (HR = 1.49; 95% CI 0.73-3.03). The risk of children born in the period 1994-2010 (a period with more comprehensive information on maternal fertility problems and with more invasive fertility treatment procedures) was increased almost twofold (HR = 1.92; 95% CI 0.92-4.00) but was still not statistically significant.

CONCLUSIONS

Our results indicate that children born to women with fertility problems, particularly after 1993, may be at an elevated risk for TNDM. As the increased risks were not statistically significant, however, the finding may be due to chance.

Mental disorders in childhood and young adulthood among children born to women with fertility problems

STUDY QUESTION

Is the risk of hospital admission or outpatient contact for mental disorders increased in children born to women with fertility problems compared with children born to women without fertility problems?

SUMMARY ANSWER

We found an increased risk of hospital admission or outpatient contact for mental disorders in children born to women with fertility problems.

WHAT IS KNOWN ALREADY

Few studies have investigated the risk of mental disorders in children born after fertility treatment and although some studies have pointed to an increased risk, others found no association. The inconsistent results may be due to methodological constraints in many previous studies, including small sample size and short follow-up, resulting in imprecise risk estimates and lack of information on risk patterns of mental disorders in adulthood.

STUDY DESIGN, SIZE, DURATION

This nationwide retrospective register-based cohort study included all 2 412 721 children born in Denmark between 1969 and 2006. All children were followed from date of birth until date of hospital contact for a mental disorder, date of emigration, date of death or 31 December 2009, whichever occurred first.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Information concerning maternal fertility status for all children in the cohort was obtained by linkage to the Danish Infertility Cohort, which contains data on nearly all women with fertility problems in Denmark since 1963. A total of 124 269 (5%) children were born to women with fertility problems and 2 288 452 (95%) to women without fertility problems. To identify children hospitalized for a mental disorder, the cohort was linked to the Danish Psychiatric Central Research Registry. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between maternal fertility status and the risk of hospital admission or outpatient contact for various groups of mental disorders, including any mental disorder and all 11 main discharge diagnostic groups, classified according to the International Classification of Diseases, version 10.

MAIN RESULTS AND THE ROLE OF CHANCE

During a mean follow-up period of 21 years (range, 0-40 years), 168 686 (7%) children were admitted to hospital or had an outpatient contact for a mental disorder. Children born to women with fertility problems had a significantly higher risk of any mental disorder (HR 1.23; 95% CI 1.20-1.26) and for most of the 11 main discharge groups, including schizophrenia (HR 1.16; 95% CI 1.07-1.27), mood (affective) disorders (HR 1.21; 95% CI 1.15-1.28) and disorders of psychological development (HR 1.15; 95% CI 1.09-1.21) as well as the subgroup of attention-deficit/hyperactivity disorders (HR 1.36; 95% CI 1.29-1.45) compared with children born to women without fertility problems. The risk estimates did not change markedly when analyses were performed separately for mental disorders diagnosed during childhood (0-19 years) and in young adulthood (20-40 years).

LIMITATIONS, REASON FOR CAUTION

The true risk of mental disorders may be somewhat underestimated, as only severe disorders requiring hospital admission or outpatient contact were considered as events. Furthermore, we could not determine whether the increased risks observed were due to factors related to the underlying infertility or to fertility treatment procedures.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first report on mental disorders in adulthood among children born to women with fertility problems. Furthermore, we have assessed the risk of several severe mental disorders not previously studied (e.g. neurotic, stress-related and somatoform disorders and disorders of adult personality and behaviour). These important findings should be investigated further in large epidemiological studies designed to differentiate between factors related to fertility treatment and to the underlying infertility.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by internal funding from the Unit of Virus, Lifestyle and Genes at the Danish Cancer Society Research Center. All authors report no conflicts of interest.

Maternal use of fertility drugs and risk of cancer in children--a nationwide population-based cohort study in Denmark

Large population-based studies are needed to examine the effect of maternal use of fertility drugs on the risk of cancer in children, while taking into account the effect of the underlying infertility. A cohort of 123,322 children born in Denmark between 1964 and 2006 to 68,255 women who had been evaluated for infertility was established. We used a case-cohort design and calculated hazard ratios (HRs) for cancer in childhood (0-19 years) and in young adulthood (20-29 years) associated with maternal use of six groups of fertility drugs (clomiphene, gonadotropins [i.e., human menopausal gonadotropins and follicle-stimulating hormone], gonadotropin-releasing hormone analogs, human chorionic gonadotropins, progesterone and other fertility drugs). We found no statistically significant association between maternal use of fertility drugs and risk for overall cancer in childhood or young adulthood. However, with regard to specific cancers in childhood, our results showed that maternal use of progesterone before childbirth markedly increased the risks of their offspring for acute lymphocytic leukemia (any use: HR, 4.95; 95% CI, 1.69-14.54; ≥ three cycles of use: HR, 9.96; 95% CI, 2.63-37.77) and for sympathetic nervous system tumors (any use: HR, 5.79; 95% CI, 1.23-27.24; ≥ three cycles of use: HR, 8.51; 95% CI, 1.72-42.19). These findings show that maternal use of progesterone may increase the risk for specific cancers in the offspring. Additional large epidemiological studies are urgently needed to confirm our finding.

Hospital contact for mental disorders in survivors of childhood cancer and their siblings in Denmark: a population-based cohort study

BACKGROUND

Survivors of childhood cancer are known to be at risk for long-term physical and mental effects. However, little is known about how cancers can affect mental health in the siblings of these patients. We aimed to assess the long-term risks of mental disorders in survivors of childhood cancer and their siblings.

METHODS

Hospital contact for mental disorders was assessed in a population-based cohort of 7085 Danish children treated for cancer by contemporary protocols between 1975 and 2010 and in their 13 105 siblings by use of data from the Danish Psychiatric Central Research Registry. Hazard ratios (HRs) for first hospital contact were calculated using a Cox proportional hazards model. We compared these sibling and survivor cohorts with two population-based cohorts who were not childhood cancer survivors or siblings of survivors.

FINDINGS

Survivors of childhood cancer were at increased risk of hospital contact for mental disorders, with HRs of 1·50 (95% CI 1·32-1·69) for males and 1·26 (1·10-1·44) for females. Children younger than 10 years at diagnosis had the highest risk, and increased risks were seen in survivors of CNS tumours, haematological malignancies, and solid tumours. Survivors had higher risk of neurodevelopmental, emotional, and behavioural disorders than population-based comparisons and siblings, and male survivors had higher risk for unipolar depression. Overall, siblings had no excess risk for mental disorders. However, our data suggest that siblings who were young at the time of cancer diagnosis of the survivor were at increased risk for mental disorders, whereas those older than 15 years at diagnosis were at a lower risk than the general population.

INTERPRETATION

Childhood cancer survivors should be followed up for mental late effects, especially those diagnosed in young age. Further, clinicians should also be aware that siblings who were young at the time of cancer diagnosis might be at increased risk for mental health disorders.

Fertility treatment and childhood cancer risk: a systematic meta-analysis

OBJECTIVE

To clarify the association between fertility treatment and the risk for cancer in children.

DESIGN

Meta-analysis.

SETTING

None.

PATIENT(S)

Twenty-five cohort and case-control studies involving children born after fertility treatment as the exposure of interest and cancer as the outcome.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Medline was searched through September 2012 to identify relevant studies. The study-specific estimates for each cancer outcome were combined into a pooled relative risk (RR) with 95% confidence interval (CI) by a meta-analytic approach.

RESULT(S)

We found that children born after fertility treatment were at increased risk for all cancers (RR = 1.33; 95% CI, 1.08-1.63) and for hematological cancers (RR = 1.59; 95% CI, 1.32-1.91), central nervous system/neural cancers (RR = 1.88; 95% CI, 1.02-3.46), and other solid cancers (RR = 2.19; 95% CI, 1.26-3.80). For specific cancer types, we found increased risks for leukemias (RR = 1.65; 95% CI, 1.35-2.01), neuroblastomas (RR = 4.04; 95% CI, 1.24-13.18), and retinoblastomas (RR = 1.62; 95% CI, 1.12-2.35) associated with fertility treatment.

CONCLUSION(S)

The results of the largest meta-analysis on this topic to date indicate an association between fertility treatment and cancer in offspring. However, our results do not rule out that factors related to underlying subfertility, rather than the procedure itself, are the most important predisposing factors for childhood cancer.

Increased risk for cancer among offspring of women with fertility problems

Some studies have indicated that children born after fertility treatment have a potential risk for cancer, but the results are inconsistent. Furthermore, any negative effects of fertility treatment might be due to the underlying infertility rather than to the procedure itself. In the largest cohort study to date with information on fertility, we examined whether the offspring of women with fertility problems had a higher risk for cancer than offspring of women without fertility problems. The study cohort consisted of 2,830,054 offspring born in Denmark between 1964 and 2006. Of these, 125,844 were offspring of women evaluated for infertility. Cox regression models were used to estimate the possible effect of being the offspring of a woman evaluated for infertility on the risk for cancer. Analyses were performed separately for cancer during childhood (0-19 years) and cancer in young adulthood (>20 years). We found that offspring born to women with fertility problems had higher overall risks for cancer in childhood (hazard ratio (HR), 1.18; 95% confidence interval (CI), 1.05-1.32) and in young adulthood (HR, 1.22; 95% CI, 1.04-1.43) than offspring of women without fertility problems. Offspring of women with fertility problems had significantly increased risks for leukemia in childhood (HR, 1.30; 95% CI, 1.06-1.60) and for cancer of the endocrine glands in young adulthood (HR, 2.67; 95% CI, 1.35-5.29). These findings suggest that offspring born to mothers with fertility problems are at increased risk for cancer in both childhood and young adulthood. If real, our findings of an ∼18% overall increase in risk for cancer in childhood and an ∼22% overall increase in risk for cancer in young adulthood would mean about four additional cases of childhood cancer and about nine additional cases of cancer in young adults per 100,000 exposed offspring.

[Continuous regular use of mild analgesics in Denmark]

INTRODUCTION

In spite of the negative health effects associated with the use of analgesics, little is known about the prevalence of continuous regular use of analgesics or about the factors associated with their use. The objective of this article is to describe continuous regular use of acetaminophen, ibuprofen and aspirin in Denmark and to examine factors associated with their use.

MATERIAL AND METHODS

The study is based on data from two surveys and includes a random sample of women and men aged 18-45 years from the general Danish population. A total of 22,199 women (response rate 81%) and 23,080 men (response-rate 71%) were included in the study. Data was analyzed using multivariate logistic regression.

RESULTS

More women than men reported a regular monthly use of acetaminophen, ibuprofen and aspirin during the past year. Acetaminophen was the most commonly used type of analgesic of which 20% of the women and 13% of the men reported a regular monthly use. Besides poor self-rated health, we found that increasing age, low level of education, living in lesser urbanized areas, smoking and being overweight were associated with a higher risk of having a continuous regular weekly use of acetaminophen, ibuprofen or aspirin.

CONCLUSION

Continuous regular use of analgesics is generally prevalent amongst young Danish men and women. This study demonstrates social inequalities in the use of analgesics, which make this a potential area for intervention that deserves further attention.

Factors associated with a continuous regular analgesic use - a population-based study of more than 45,000 Danish women and men 18-45 years of age

PURPOSE

Widespread use of and serious adverse effects associated with use of analgesics accentuates the need to consider factors related to analgesic use. The objective of this study was to describe continuous regular analgesics use and examine factors associated with a continuous regular analgesic use.

METHODS

The study was based on data from two surveys and included a random sample of women and men aged 18-45 years from the general Danish population. Information on analgesics use, self-rated health, demographic and lifestyle factors was collected using a self-administered questionnaire. A total of 28,000 women and 33 000 men were invited to participate and 22,199 women (response-rate 81.4%) and 23,080 men (response-rate 71.0%), respectively, were included in the study. Data were analyzed using multivariate logistic regression.

RESULTS

We found that 27% of the women and 18% of the men reported a regular monthly use of at least seven analgesic tablets during the last year (continuous regular analgesics use). Besides poor self-rated health we found in both sexes that increasing age, poor self-rated fitness, and smoking were related to a continuous regular analgesics use. Nulliparity, low level of education, overweight/obesity, binge drinking, and abstinence were associated with a continuous regular analgesics use for women, while underweight and marital/cohabiting status were associated with a continuous regular analgesics use only for men.

CONCLUSIONS

Regular monthly analgesic use during the last year was generally prevalent. Besides self-rated health, several socio-demographic and lifestyle factors were associated with a continuous regular analgesic use, although with some gender differences.

[Gender differences in stress among physicians]

INTRODUCTION

It is difficult to evaluate gender differences in relation to health because occupation and position are different for males and females. It is therefore necessary to evaluate how health is affected for both genders with the same working conditions. The purpose of this study was to evaluate: 1) gender differences in relation to different stressors within daily life, working life and health, 2) how these stressors affect the correlation between stress and gender.

MATERIALS AND METHOD

A questionnaire was sent out in 2001 to a total of 1414 physicians; 707 males and 707 females. The response rate was 58%. Using SPSS, the answers were reviewed by gender differences in relation to selected stressors in daily life, working life and health. Finally, a logistic regression was run where the correlation between gender and stress was controlled for all significant stressors.

RESULTS

It was found that female physicians more often experience stressors in relation to daily life and health while male physicians experience stressors in relation to their working life. It was also shown that female physicians had more than twice the risk of being stressed on a daily basis compared to male physicians, when controlling for cohabitant/spouse working hours, own working hours, conflicting demands at work, the feeling of never having enough time for oneself and depression.

CONCLUSION

Female physicians had more than twice the risk of being stressed on a daily basis compared to their male colleagues, in spite of control for stressors in relation to daily life, working life and health.

[Gender and stress]

Stress is an independent risk factor for developing e.g. heart diseases and depression. There are marked gender differences which need to be examined in depth. Some of the explanation seems to be related to the traditional pattern of gender roles--men as breadwinners and women with responsibility for the family as well as paid work in addition to housework. But gender differences in biological factors also seem to play an important role in chronic stress and stress-related diseases. We need to know more about gender differences, but we can already incorporate the known ones in the prevention of stress-related disorders.