The association between fertility treatments and the incidence of paediatric cancer: A systematic review and meta-analysis

Medically Assisted Reproduction and Risk of Cancer Among Offspring

Importance

Cancer is a leading cause of death among children worldwide. Treatments used for medically assisted reproduction (MAR) are suspected risk factors because of their potential for epigenetic disturbance and associated congenital malformations.

Objective

To assess the risk of cancer, overall and by cancer type, among children born after MAR compared with children conceived naturally.

Design, Setting, and Participants

For this cohort study, the French National Mother-Child Register (EPI-MERES) was searched for all live births that occurred in France between January 1, 2010, and December 31, 2021 (and followed up until June 30, 2022). The EPI-MERES was built from comprehensive data of the French National Health Data System. Data analysis was performed from December 1, 2021, to June 30, 2023.

Exposure

Use of assisted reproduction technologies (ART), such as fresh embryo transfer (ET) or frozen ET (FET), and artificial insemination (AI).

Main Outcomes and Measures

The risk of cancer was compared, overall and by cancer type, among children born after fresh ET, FET, or AI and children conceived naturally, using Cox proportional hazards regression models adjusted for maternal and child characteristics at birth.

Results

This study included 8 526 306 children with a mean (SD) age of 6.4 (3.4) years; 51.2% were boys, 96.4% were singletons, 12.1% were small for gestational age at birth, and 3.1% had a congenital malformation. There were 260 236 children (3.1%) born after MAR, including 133 965 (1.6%) after fresh ET, 66 165 (0.8%) after FET, and 60 106 (0.7%) after AI. A total of 9256 case patients with cancer were identified over a median follow-up of 6.7 (IQR, 3.7-9.6) years; 165, 57, and 70 were born after fresh ET, FET, and AI, respectively. The overall risk of cancer did not differ between children conceived naturally and those born after fresh ET (hazard ratio [HR], 1.12 [95% CI, 0.96 to 1.31]), FET (HR, 1.02 [95% CI, 0.78 to 1.32]), or AI (HR, 1.09 [95% CI, 0.86 to 1.38]). However, the risk of acute lymphoblastic leukemia was higher among children born after FET (20 case patients; HR 1.61 [95% CI, 1.04 to 2.50]; risk difference [RD], 23.2 [95% CI, 1.5 to 57.0] per million person-years) compared with children conceived naturally. Moreover, among children born between 2010 and 2015, the risk of leukemia was higher among children born after fresh ET (45 case patients; HR, 1.42 [95% CI, 1.06 to 1.92]; adjusted RD, 19.7 [95% CI, 2.8 to 43.2] per million person-years).

Conclusions and Relevance

The findings of this cohort study suggest that children born after FET or fresh ET had an increased risk of leukemia compared with children conceived naturally. This risk, although resulting in a limited number of cases, needs to be monitored in view of the continuous increase in the use of ART.

Long-term health risk of offspring born from assisted reproductive technologies

Since the world's first in vitro fertilization baby was born in 1978, there have been more than 8 million children conceived through assisted reproductive technologies (ART) worldwide, and a significant proportion of them have reached puberty or young adulthood. Many studies have found that ART increases the risk of adverse perinatal outcomes, including preterm birth, low birth weight, small size for gestational age, perinatal mortality, and congenital anomalies. However, data regarding the long-term outcomes of ART offspring are limited. According to the developmental origins of health and disease theory, adverse environments during early life stages may induce adaptive changes and subsequently result in an increased risk of diseases in later life. Increasing evidence also suggests that ART offspring are predisposed to an increased risk of non-communicable diseases, such as malignancies, asthma, obesity, metabolic syndrome, diabetes, cardiovascular diseases, and neurodevelopmental and psychiatric disorders. In this review, we summarize the risks for long-term health in ART offspring, discuss the underlying mechanisms, including underlying parental infertility, epigenetic alterations, non-physiological hormone levels, and placental dysfunction, and propose potential strategies to optimize the management of ART and health care of parents and children to eliminate the associated risks. Further ongoing follow-up and research are warranted to determine the effects of ART on the long-term health of ART offspring in later life.

Polygenic embryo screening: are there potential maternal and fetal harms?

Polygenic embryo screening (PES) and its derivate the Embryo Health Score (EHS) have generated interest in both infertile and fertile populations due to their potential ability to select embryos with a reduced risk of disease and improved long-term health outcomes. Concerns have been raised regarding the potential harms of IVF itself, including possible epigenetic changes that may affect the health of the offspring in late adulthood, which are not fully captured in the EHS calculation. Knowledge of the potential impacts of the trophectoderm biopsy, which is a key component of the PES procedure, on the offsprings' health is limited by the heterogeneity of the population characteristics used in the published studies. Nonetheless, the literature suggests a possible increased risk of preterm delivery, birth defects and pre-eclampsia after trophectoderm biopsy. Overall, the risks of PES for prenatal and postnatal health remain uncertain, and further research is needed. Counselling patients regarding these risks before considering PES is important, to provide an understanding of the risks and benefits. This review aims to highlight some of these issues, the need for continued investigation in this area, and the importance of informed decision-making in the context of PES.

Current status and reflections on fertility preservation in China

PURPOSE

With the progress of medical technology and renovated conception of fertility, the prospective studies and practice of fertility preservation are drawing more and more attention from medical workers. With the largest population of over 1.4 billion, China makes the experience accumulated in fertility preservation efforts even more relevant. This article summarizes China's experience and shares it with the world to promote the healthy development of fertility preservation.

METHODS

This study was based on multiple Chinese expert consensuses on fertility preservation issued in 2021 and the current national regulations and principles, compared with the latest advice and guidelines issued by global reproductive authorities such as the ASRM and ESHRE. Summarize the experience and reflection of Chinese scholars in the process of fertility preservation.

RESULTS

This study reports on the current situation of fertility preservation in China, sharing the Chinese experience gained in the process of development, and offering Chinese reflections on worrying issues.

CONCLUSION

Fertility preservation is a medical and social issue of reproductive health security, which is conducive to the sound development of the world population and social production.

Health of singletons born after frozen embryo transfer until early adulthood: a Finnish register study

STUDY QUESTION

Is the health of singletons born after frozen embryo transfer (FET) comparable to that of singletons born after fresh embryo transfer (ET) until early adulthood?

SUMMARY ANSWER

The health of singletons born after FET does not differ from that of singletons born after fresh ET.

WHAT IS KNOWN ALREADY

The differences in perinatal outcomes of children born after FET and fresh ET are well known. FET is associated with an increased risk of large-for-gestational-age but diminished risks of preterm birth (PTB), small-for-gestational-age and decreased perinatal mortality compared to fresh ET. However, knowledge on the long-term health after FET is scarce.

STUDY DESIGN, SIZE, DURATION

This retrospective register-based cohort study compares singletons born after FET (n = 1825) between the years 1995 and 2006 to those born after fresh ET (n = 2933) and natural conception (NC, n = 31 136) with a mean follow-up time of 18-20 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Singletons born after FET were compared to those born after fresh ET and NC regarding the frequencies of diagnoses in the main ICD-10 chapters (International Statistical Classification of Diseases and Related Health Problems, 10th revision), the number of outpatient visits and hospital admissions, and mortality. Adjustments were made for PTB, maternal age, parity, socioeconomic status based on mother's occupation and offspring sex. The study combines data from the Finnish Medical Birth Register, the Finnish Care Register for Health Care (CRHC) and the Cause-of-Death Register at Statistics Finland. The Student's T-test was used for continuous variables, and the Chi-square test was used for categorical variables. Cox regression was used to estimate crude and adjusted hazard ratios (HRs and aHRs, respectively). A general linear model was used to compare the means of outpatient visits, hospital admissions and lengths of hospital stays per person.

MAIN RESULTS AND THE ROLE OF CHANCE

No significant differences between the FET and fresh ET groups were found in the frequency of diagnoses in any of the ICD-10 chapters or in the parameters describing the need for hospital care. However, compared to the NC group, higher proportions in the FET group had outpatient visits in the hospital (93.5% vs 92.2%, aHR 1.23, 95% CI 1.17, 1.30) or hospital admissions (48% vs 46.5%, aHR 1.28, 95% CI 1.19, 1.37). Compared to the NC group, the FET group had elevated adjusted risks of diagnoses of infectious and parasitic diseases (aHR 1.24; 95% CI 1.11, 1.38), neoplasms (aHR 1.68; 95% CI 1.48, 1.91), diseases of the eye and adnexa, the ear or mastoid process (aHR 1.11; 95% CI 1.01, 1.21), the respiratory system (aHR 1.15; 95% CI 1.06, 1.23), the digestive system (aHR 1.17; 95% CI 1.05, 1.32), the skin or subcutaneous tissue (aHR 1.28; 95% CI 1.14, 1.43) and the genitourinary system (aHR 1.27; 95% CI 1.11, 1.45), as well as congenital malformations or chromosomal abnormalities (aHR 1.31; 95% CI 1.14, 1.50) and symptoms, signs or abnormal clinical or laboratory findings (aHR 1.25, 95% CI 1.16, 1.34).

LIMITATIONS, REASONS FOR CAUTION

Only hospital-based inpatient and outpatient care is covered by the CRHC register, excluding milder cases diagnosed elsewhere. We were not able to study the effect of ART treatments and subfertility separately in our setting. In addition, although our cohort is reasonably sized, even larger cohorts would be needed to reliably study rare outcomes, such as cancer.

WIDER IMPLICATIONS OF THE FINDINGS

For many ICD-10 chapters, we present the first published data on the long-term outcome of singletons born after FET. The results on FET versus fresh ET are reassuring, whereas the results on FET versus NC warrant further investigation.

STUDY FUNDING/COMPETING INTEREST(S)

Finnish government research funding was obtained for this study. Funding was also obtained from the Finnish Medical Society Duodecim, the Päivikki and Sakari Sohlberg Foundation, Orion Research Foundation, Finnish Society of Obstetrics and Gynaecology (research grants to A.M.T.) and Finnish government research funding. The funding sources were not involved in the planning or execution of the study. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Cancer in children born after frozen-thawed embryo transfer: A cohort study

BACKGROUND

The aim was to investigate whether children born after assisted reproduction technology (ART), particularly after frozen-thawed embryo transfer (FET), are at higher risk of childhood cancer than children born after fresh embryo transfer and spontaneous conception.

METHODS AND FINDINGS

We performed a registry-based cohort study using data from the 4 Nordic countries: Denmark, Finland, Norway, and Sweden. The study included 7,944,248 children, out of whom 171,774 children were born after use of ART (2.2%) and 7,772,474 children were born after spontaneous conception, representing all children born between the years 1994 to 2014 in Denmark, 1990 to 2014 in Finland, 1984 to 2015 in Norway, and 1985 to 2015 in Sweden. Rates for any cancer and specific cancer groups in children born after each conception method were determined by cross-linking national ART registry data with national cancer and health data registries and population registries. We used Cox proportional hazards models to estimate the risk of any cancer, with age as the time scale. After a mean follow-up of 9.9 and 12.5 years, the incidence rate (IR) of cancer before age 18 years was 19.3/100,000 person-years for children born after ART (329 cases) and 16.7/100,000 person-years for children born after spontaneous conception (16,184 cases). Adjusted hazard ratio (aHR) was 1.08, 95% confidence interval (CI) 0.96 to 1.21, p = 0.18. Adjustment was performed for sex, plurality, year of birth, country of birth, maternal age at birth, and parity. Children born after FET had a higher risk of cancer (48 cases; IR 30.1/100,000 person-years) compared to both fresh embryo transfer (IR 18.8/100,000 person-years), aHR 1.59, 95% CI 1.15 to 2.20, p = 0.005, and spontaneous conception, aHR 1.65, 95% CI 1.24 to 2.19, p = 0.001. Adjustment either for macrosomia, birth weight, or major birth defects attenuated the association marginally. Higher risks of epithelial tumors and melanoma after any assisted reproductive method and of leukemia after FET were observed. The main limitation of this study is the small number of children with cancer in the FET group.

CONCLUSIONS

Children born after FET had a higher risk of childhood cancer than children born after fresh embryo transfer and spontaneous conception. The results should be interpreted cautiously based on the small number of children with cancer, but the findings raise concerns considering the increasing use of FET, in particular freeze-all strategies without clear medical indications.

TRIAL REGISTRATION

Trial registration number: ISRCTN 11780826.

Assisted Reproductive Technology and Risk of Childhood Cancers

IMPORTANCE

The number of children born through the use of assisted reproductive technology (ART) has been increasing. These children may have higher risks for epigenetic alteration and adverse perinatal outcomes, which may be associated with childhood cancers.

OBJECTIVE

To determine the associations between different modes of conception and childhood cancers and potential mediation by preterm birth and low birth weight.

DESIGN, SETTING, AND PARTICIPANTS

This nationwide, population-based cohort study included registry data from 2 308 016 eligible parents-child triads in Taiwan from January 1, 2004, to December 31, 2017. A total of 1880 children with incident childhood cancer were identified. Data were analyzed between September 1, 2020, and June 30, 2022.

EXPOSURE

Mode of conception, defined as (1) natural conception, (2) subfertility and non-ART (ie, infertility diagnosis but no ART-facilitated conception), or (3) ART (ie, infertility diagnosis and ART-facilitated conception).

MAIN OUTCOMES AND MEASURES

Diagnosis of childhood cancer according to the International Classification of Childhood Cancers, Third Edition.

RESULTS

The mean (SD) paternal and maternal ages were 33.28 (5.07) and 30.83 (4.56) years, respectively. Of the 2 308 016 children, 52.06% were boys, 8.16% were born preterm, and 7.38% had low birth weight. During 14.9 million person-years of follow-up (median, 6 years [IQR, 3-10 years]), ART conception was associated with an increased risk of any type of childhood cancers compared with natural conception (hazard ratio, 1.58; 95% CI, 1.17-2.12) and subfertility with non-ART conception (hazard ratio, 1.42; 95% CI, 1.04-1.95). The increased cancer risk of children conceived with ART was mainly owing to leukemia and hepatic tumor. The increased cancer risk associated with ART conception was not mediated by preterm birth or low birth weight.

CONCLUSIONS AND RELEVANCE

In this cohort study, children conceived via ART had a higher risk of childhood cancers than those conceived naturally and those born to parents with an infertility diagnosis did not use ART. The increased risk could not be explained by preterm birth or low birth weight.

Neonatal Adverse Outcomes of Induction and Expectant Management in Fetal Growth Restriction: A Systematic Review and Meta-Analysis

Background and Objective: Fetal growth restriction (FGR) is a pathological condition in which the fetus cannot reach its expected growth potential. When it is diagnosed as a suspected FGR, it remains an unsolved problem whether to direct induction or continue expectant management. To effectively reduce the incidence of neonatal adverse outcomes, we aimed to evaluate whether either method was associated with a lower incidence of neonatal adverse outcomes. Methods: We searched the relevant literature through the PubMed, Web of Science, and Cochrane Library from inception to January 10, 2020. We defined induction as the experimental group and expectant management as the control group. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using random-effects models owing to heterogeneity. Furthermore, we conducted a sensitivity analysis to explore the robustness of the included literature. We used the Newcastle-Ottawa scale (NOS) to evaluate the quality of the available studies. We applied the funnel plot to describe the publication bias. Additionally, subgroup analysis based on the study method, sample size, area, NOS score, Apgar score <7 at 5 min, definition of suspected FGR, severity, and neonatal adverse outcomes were performed to further evaluate the differences between the induction and expectant management. Results: Our study included a total of eight articles with 6,706 patients, which consisted of four randomized controlled trials (RCTs), three retrospective cohort studies, and one prospective cohort study. The total pooled OR and 95% CI between the induction group and the expected management group was 1.38 (95% CI, 0.84-2.28) in the random model. The heterogeneity was I 2 = 84%, P < 0.01. The sensitivity analysis showed that the neonatal adverse outcomes of induction vs. expectant management still presented similar outcomes after omitting of any one of these studies. The funnel plot and linear regression equation showed that there was no publication bias in our study (P = 0.75). Subgroup analysis showed that induction increased the neonatal adverse outcome risks of hypoglycemia and respiratory insufficiency (ORneonatal hypoglycaemia = 8.76, 95% CI: 2.57-29.90; ORrespiratory insufficiency = 1.74, 95% CI: 1.35-2.24, respectively). However, no significant differences were observed based on the other subgroups (all P > 0.05). Conclusion: Regardless of induction or expectant management of a suspected FGR, the neonatal adverse outcomes showed no obvious differences. More studies should be conducted and confounding factors should be taken into consideration to elucidate the differential outcomes of the two approaches for suspected FGR.