Cohort differences in physical health and disability in the United States and Europe.

OBJECTIVES: Declines in mortality have historically been associated with improvements in physical health across generations. While life expectancy in most high-income countries continues to increase, there is evidence that younger generations, particularly in the United States (US), are less healthy than previous generations at the same age. We compared generational trends in physical health in the US, England, and continental Europe to explore whether other regions have experienced a similar pattern of worsening health across cohorts. METHODS: Using data from nationally representative studies of adults aged ≥50 years from the US (Health and Retirement Study, n=26,939), England (English Longitudinal Study of Ageing, n=14,992) and 11 continental European countries (Survey of Health, Ageing and Retirement in Europe, n=72,595), we estimated differences in the age-adjusted prevalence of self-reported chronic disease and disability and observer-measured health indicators across pseudo-birth cohorts (born <1925, 1925-1935, 1936-1945, 1946-1954, 1955-1959). RESULTS: Age-adjusted prevalence of doctor-diagnosed chronic disease increased across successive cohorts in all regions. Trends in disability prevalence were more regionally varied. Still, in both the US and Europe, we observed a structural break in disability trends, with declines observed in pre-war cohorts slowing, stalling, or reversing for cohorts born since 1945. DISCUSSION: In all regions, we found evidence for worsening health across cohorts, particularly for those born since 1945. While more chronic disease in younger cohorts need not necessarily translate to worse quality of life or higher rates of functional limitation, there is some suggestion that worsening chronic disease morbidity may be spilling over into worsening disability.

Gradients in low birthweight by maternal education: A comparative perspective.

Background: Longstanding research has shown strong inequalities in low birthweight by household income. However, most such research has focused on Anglophone countries, while evidence emerging from other developed countries suggest a stronger role of education rather than incomes in creating inequalities at birth. This paper compares gradients in low birthweight by maternal education, as well as explores underlying mechanisms contributing to these gradients, in France, the United States, and the United Kingdom. Methods: Analyses are based on harmonized data from large, nationally-representative samples from France, UK and US. We use regression models and decomposition methods to explore the relative role of several possible mechanisms in producing birthweight inequalities. Results: Inequalities in low birth weight across maternal education groups were relatively similar in the United States, the United Kingdom and France. However, the individual-level mechanisms producing such inequalities varied substantially across the three countries, with income being most important in the US, pregnancy smoking being most evident in France, and the UK occupying an intermediate position. Differences in the mechanisms producing birth health inequalities mirror differences in the policy environment in the three countries. Conclusion: While inequalities in health appear from the earliest moments in many countries, our results suggest research on birth health inequalities, and therefore policies, is not easily generalizable across national contexts, and call for more scholarship in uncovering the "whys" of health inequalities in a variety of contexts.

Educational gradients in the prevalence of medically assisted reproduction births in a comparative perspective.

OBJECTIVE: To study educational gradients in births after medical assisted reproduction across five countries with different institutional arrangements. DESIGN: We use logistic regression and compute predicted probabilities to estimate the association between education and giving birth after assisted reproduction, before and after adjustment for maternal age at delivery and marital/partnership status, using an overall sample of about 3.9 million live births in five countries. SUBJECTS: This study includes survey or register data containing information on births in five countries: N=61, 564 for Denmark, N= 37,533 for France, N=12,889 for Spain, N= 17,097 for the United Kingdom, and N=3,700,442 for the United States. INTERVENTION (FOR RCT) OR EXPOSURE (FOR OBSERVATIONAL STUDIES): None. MAIN OUTCOME MEASURES: Probability of a child being born after medically assisted reproduction for mothers with a university degree relative to those having less than a university degree. RESULTS: University educated mothers are more likely to give birth after assisted reproduction compared to mothers with lower levels of education. After adjustment for socio-demographic characteristics, educational differences disappear in the United Kingdom and to some extent Spain, whilst they attenuate but persist in the other countries. The United States seems to show a larger educational gradient. CONCLUSION: The results suggest that the institutional setting around assisted reproduction may moderate the gradient. A possible explanation may be access to treatments, as the United States - the context with the lowest subsidization - seems to show larger educational gradients than other contexts. In a context of global postponement of childbearing to older ages, mothers with lower levels of socioeconomic resources might find it more difficult to fully realise their fertility intentions in countries with a less generous subsidization of treatments.

Defining and Identifying Only Children: A Research Note on the Concept and Measurement Illustrated With UK Survey Data.

Despite increasing interest in the circumstances and outcomes of only children in the demographic literature, the conceptualization of this group has received limited scholarly attention. This research note argues for greater engagement by demographers and social scientists in the conceptualization and identification of only children by addressing three aims. First, we outline potential definitions of only children, present a framework to guide researchers' decisions, and evaluate whether only children can be reliably identified using the British birth cohort studies. Second, we show that the prevalence estimates are contingent on the timing of measurement in childhood, indicating the need for caution when deriving only-child status from cross-sectional household grid data. Third, we demonstrate that both the size and the characteristics of the only-child group may differ across definitions, highlighting that the accurate operationalization of some definitions is particularly restricted by survey designs that prioritize mothers for data collection on children and families. We argue that researchers interested in sole children's outcomes must choose the most appropriate measure for a given research question and, given that many datasets limit how accurately any indicator of only children can capture the chosen definition, reflect on how the operationalization of their measure might affect the results.

Generational differences in physical health and disability in the United States and Europe.

Objectives: Declines in mortality have typically been associated with improvements in physical health across generations. While life expectancy in most high-income countries continues to increase, there is evidence that younger generations, particularly in the United States (US), are less healthy than previous generations at the same age. We compared generational trends in physical health in the US, England, and continental Europe to explore whether other regions have experienced a similar pattern of worsening health across cohorts. Methods: Using data from nationally representative studies of adults aged ≥50 years from the US (Health and Retirement Study, n=26,939), England (English Longitudinal Study of Ageing, n=14,992) and 11 continental European countries (Survey of Health, Ageing and Retirement in Europe, n=72,595), we estimated differences in the age-adjusted prevalence of self-reported chronic disease and disability and observer-measured health indicators across pseudo-birth cohorts (born <1925, 1925-1935, 1936-1945, 1946-1954, 1955-1959). Results: Age-adjusted prevalence of doctor-diagnosed chronic disease increased across cohorts in all regions. Trends in disability prevalence were more regionally varied. Still, in both the US and Europe, we observed a structural break in disability trends, with declines observed in pre-war cohorts slowing, stalling, or reversing for cohorts born since 1945. Discussion: In all regions, we found evidence for worsening health across cohorts, particularly for those born since 1945. While more chronic disease in younger cohorts need not necessarily translate to worse quality of life or higher rates of functional limitation, there is some suggestion that worsening chronic disease morbidity may be spilling over into worsening disability.

Medically assisted reproduction and mental health in adolescence: evidence from the UK Millennium Cohort Study.

BACKGROUND: The number and proportion of children conceived through medically assisted reproduction (MAR) is steadily increasing yet the evidence on their mental health in adolescence is inconclusive. Two main mechanisms with opposite effects can explain differences in mental health outcomes by conception mode: while more advantaged parental characteristics could positively influence it, higher parental stress could have a negative influence. METHODS: Linear and logistic estimations on a longitudinal population-based birth cohort study of 9,897 individuals to investigate whether adolescents conceived through MAR are more likely than naturally conceived (NC) children to experience mental health problems at age 17, as reported by adolescents themselves and their parents. We test whether this association is confounded and/or mediated by parental background characteristics collected when the cohort member was around 9 months old (maternal age, maternal education level, ethnicity, income quintile), family structure variables measured in adolescence (number of siblings in the household at age 15, parental household structure at age 14) or maternal distress at age 14. RESULTS: Children conceived naturally and through MAR self-reported similar mental health outcomes. The only differences between MAR and NC adolescents are in the parental reports, with parents who conceived through MAR reporting their children had 3.82 (95% CI: 1.140 to 11.54) and 2.35 (95% CI: 1.145 to 4.838) higher odds of falling within the high category of SDQ total difficulties and emotional symptoms scales, respectively. The results did not change on adjustment for mediators, such as maternal distress, number of siblings in the household and parental household structure. CONCLUSIONS: The results reveal a lack of or small differences in MAR adolescents' mental health outcomes compared to children who were conceived naturally. While the results based on the parental reports could suggest that MAR adolescents are at higher risk of suffering from mental health problems, the differences are small and not supported by adolescents' own reports. The difference between MAR and NC adolescent's parental report might reflect differences in parental concern, their relationship or closeness and can help to reconcile the mixed findings of previous studies.

Partnership trajectories preceding medically assisted reproduction.

The number of people who undergo medically assisted reproduction (MAR) to conceive has increased considerably in recent decades. However, existing research into the demographics and the partnership histories of this growing subgroup is limited. Using unique data from Finnish population registers on nulliparous women born in Finland in 1971-77 (n = 21,129; ∼10 per cent of all women) who had undergone MAR treatment, we created longitudinal partnership histories from age 16 until first MAR treatment. We identified six typical partnership trajectories and used relative frequency sequence plots to investigate heterogeneity in partnership transitions within and between these groups. The majority of women (60.7 per cent) underwent MAR with their first partner, followed by women who underwent MAR in a second (21.5 per cent) or higher-order partnership (7.1 per cent), while 10.7 per cent underwent MAR without a partner. On average, women undergoing MAR were relatively young (with around half starting treatment before age 30) and were highly educated with high incomes.

Loneliness during the Pregnancy-Seeking Process: Exploring the Role of Medically Assisted Reproduction.

This study explores whether undergoing medically assisted reproduction (MAR) is associated with experiencing loneliness and whether this association varies by gender and having a live birth. Using two waves of the Generations and Gender Survey (n = 2,725) from countries in Central and Eastern Europe, we estimate the changes in levels of emotional and social loneliness among pregnancy seekers in heterosexual relationships and test if they vary by the mode of conception while controlling for individual sociodemographic characteristics. Individuals who underwent MAR experienced increased levels of social loneliness compared to individuals who were trying to conceive spontaneously. This association is entirely driven by respondents who did not have a live birth between the two observation periods, while the results did not differ by gender. No differences emerged in emotional loneliness. Our findings suggest that increased social loneliness during the MAR process might be attributable to infertility-related stress and stigma.

Birth Outcomes Following Assisted Reproductive Technology Conception Among Same-Sex Lesbian Couples vs Natural Conception and Assisted Reproductive Technology Conception Among Heterosexual Couples.

This study uses registry data to compare birth outcomes, including birth weight, gestational age, low birth weight, and preterm delivery, in assisted reproductive technology (ART) pregnancies among same-sex lesbian couples vs natural conceptions and ART pregnancies among heterosexual couples.

ART and the forgotten siblings: a call for research.

A broader definition of infertility is the incapacity to have the intended number of children. However, most literature on ART exclusively focuses on live birth as an outcome, rather than on the capacity to fully realize the reproductive wishes of the couples. This issue has probably received scant attention because the total fertility rate is below replacement levels in affluent countries, and one may simplistically assume that only a minority of couples may be interested in more than one child. This assumption, however, is unproven and presumably erroneous. Unfortunately, evidence on the rate of return in couples who conceived their first child with ART is scant and information on the intended number of children in infertile couples is lacking. In general, we plea for more research on this subject. The documentation of an intended number of children above two and a high return rate in infertile couples may lead to changes in clinical practice, such as the storage of oocytes or embryos prior to initiating embryo transfers. This could improve the chance of conceiving the second child when the couple comes back some years later. In addition, the identification of the determinants for non-return as well as those explaining the gap between the intended and the realized number of children may reveal specific barriers and possibly how to tackle them. However, at present, available evidence is insufficient to advocate any intervention. Thorough research is warranted.

Health outcomes of only children across the life course: An investigation using Swedish register data.

Only children (with no full biological siblings) are a growing subgroup in many high-income settings. Previous studies have largely focused on the short-term developmental outcomes of only children, but there is limited evidence on their health outcomes. Using Swedish population register data for cohorts born 1940-75, we compare the health of only children with that of children from multi-child sibling groups, taking into account birth order, family size, and presence of half-siblings. Only children showed lower height and fitness scores, were more likely to be overweight/obese in late adolescence, and experienced higher later-life mortality than those with one or two siblings. However, only children without half-siblings were consistently healthier than those with half-siblings, suggesting that parental disruption confers additional disadvantages. The health disadvantage was attenuated but not fully explained by adjustment for parental characteristics and after using within-family maternal cousin comparison designs.

Medically assisted reproduction and mental health: a 24-year longitudinal analysis using Finnish register data.

BACKGROUND: Medically assisted reproduction can negatively affect women's mental health, particularly when the treatments do not result in a live birth. Although the number of women relying on medically assisted reproduction to conceive has grown rapidly, our knowledge about the mental health effects before, during, and after treatment is limited. OBJECTIVE: This study aimed to understand the long-term association between medically assisted reproduction and mental health outcomes for women before, during, and after their treatments, and according to whether the treatment resulted in a live birth. STUDY DESIGN: Using Finnish register data for the period from 1995 to 2018, we estimated the probability of psychotropic purchases (antidepressants, anxiolytics, hypnotics, and sedatives) for 3 groups of women who: (1) gave birth after natural conception, (2) gave birth after medically assisted reproduction treatments, or (3) underwent medically assisted reproduction but remained childless. We followed up women for up to 12 years before and 12 years after the reference date, which corresponded to the conception date for women who had a first live birth either after a natural or a medically assisted conception, or the date of the last medically assisted reproduction treatment for women with no live birth by the end of 2017. We estimated linear probability models before and after adjustment for sociodemographic characteristics. RESULTS: The results show that women who did not have a live birth after undergoing medically assisted reproduction treatments purchased more psychotropics than women who gave birth after conceiving naturally or through medically assisted reproduction, and that these differences did not attenuate over time. Twelve years after the reference date, 17.73% (95% confidence interval, 16.82-18.63) of women who underwent medically assisted reproduction but remained childless purchased psychotropics vs 11.11% of women who gave birth after natural conception (95% confidence interval, 10.98-11.26) and 12.17% (95% confidence interval, 11.65-12.69) of women who gave birth after medically assisted reproduction treatments. In addition, women who conceived naturally and through medically assisted reproduction had very similar psychotropic use patterns from 3 years before conception to 4 years after, and over the long term. Adjustment for women's sociodemographic characteristics did not change the results. CONCLUSION: The similarities in psychotropic purchases of women who had a live birth, whether naturally or through medically assisted reproduction, suggest that the higher psychotropic use among women who remained childless after undergoing medically assisted reproduction were likely driven more by involuntary childlessness than by treatment-related stress. The results highlight the importance of counseling for women undergoing medically assisted reproduction treatments, especially if their attempts to conceive are unsuccessful.

Maternal age and the risk of low birthweight and pre-term delivery: a pan-Nordic comparison.

BACKGROUND: Advanced maternal age at birth is considered a risk factor for adverse birth outcomes. A recent study applying a sibling design has shown, however, that the association might be confounded by unobserved maternal characteristics. METHODS: Using total population register data on all live singleton births during the period 1999-2012 in Denmark (N = 580 133; 90% population coverage), Norway (N = 540 890) and Sweden (N = 941 403) and from 2001-2014 in Finland (N = 568 026), we test whether advanced maternal age at birth independently increases the risk of low birthweight (LBW) (<2500 g) and pre-term birth (<37 weeks gestation). We estimated within-family models to reduce confounding by unobserved maternal characteristics shared by siblings using three model specifications: Model 0 examines the bivariate association; Model 1 adjusts for parity and sex; Model 2 for parity, sex and birth year. RESULTS: The main results (Model 1) show an increased risk in LBW and pre-term delivery with increasing maternal ages. For example, compared with maternal ages of 26-27 years, maternal ages of 38-39 years display a 2.2, 0.9, 2.1 and 2.4 percentage point increase in the risk of LBW in Denmark, Finland, Norway and Sweden, respectively. The same patterns hold for pre-term delivery. CONCLUSIONS: Advanced maternal age is independently associated with higher risk of poor perinatal health outcomes even after adjusting for all observed and unobserved factors shared between siblings.

The Well-Being of Adolescents Conceived Through Medically Assisted Reproduction: A Population-Level and Within-Family Analysis.

Medically assisted reproduction (MAR) plays an increasingly important role in the realization of fertility intentions in advanced societies, yet the evidence regarding MAR-conceived children's longer-term well-being remains inconclusive. Using register data on all Finnish children born in 1995-2000, we compared a range of social and mental health outcomes among MAR- and naturally conceived adolescents in population-averaged estimates, and within families who have conceived both through MAR and naturally. In baseline models, MAR-conceived adolescents had better school performance and the likelihood of school dropout, not being in education or employment, and early home-leaving were lower than among naturally conceived adolescents. No major differences were found in mental health and high-risk health behaviours. Adjustment for family sociodemographic characteristics attenuated MAR adolescents' advantage in social outcomes, while increasing the risk of mental disorders. The higher probability of mental disorders persisted when comparing MAR adolescents to their naturally conceived siblings. On average, MAR adolescents had similar or better outcomes than naturally conceived adolescents, largely due to their more advantaged family backgrounds, which underscores the importance of integrating a sociodemographic perspective in studies of MAR and its consequences.

Investigating change across time in prevalence or association: the challenges of cross-study comparative research and possible solutions.

Cross-study research initiatives to understand change across time are an increasingly prominent component of social and health sciences, yet they present considerable practical, analytical and conceptual challenges. First, we discuss the key challenges to comparative research as a basis for detecting societal change, as well as possible solutions. We focus on studies which investigate changes across time in outcome occurrence or the magnitude and/or direction of associations. We discuss the use and importance of such research, study inclusion, sources of bias and mitigation, and interpretation. Second, we propose a structured framework (a checklist) that is intended to provide guidance for future authors and reviewers. Third, we outline a new open-access teaching resource that offers detailed instruction and reusable analytical syntax to guide newcomers on techniques for conducting comparative analysis and data visualisation (in both R and Stata formats). Supplementary Information: The online version contains supplementary material available at 10.1007/s44155-022-00021-1.

Parental fecundability and neurodevelopmental delays and difficulties in offspring.

BACKGROUND: Impaired neurodevelopment is reported among children conceived by assisted reproductive technologies (ART). However, this might be explained by conditions underlying parental subfecundity, rather than the ART procedure. METHODS: We examined associations of parental time-to-pregnancy (TTP) and conception by ART with neurodevelopmental traits up to 8 years of age, including motor and language skills, social delays and difficulties, and inattention-hyperactivity, among 92 142 singletons participating in the Norwegian Mother, Father and Child Cohort Study (MoBa). Mothers reported TTP and neurodevelopmental traits through questionnaires. Mean differences in standardized neurodevelopmental traits were estimated using linear regression, adjusting for maternal age, parity, educational level, body mass index and smoking, and paternal age. RESULTS: A longer TTP was associated with decreased language skills and motor skills at 6, 18 and 36 months (P-values for trend ≤0.01), prosocial skills delay at 36 months (P-values for trend ≤0.001) and increased scores for inattention-hyperactivity traits at all ages up to 8 years (P-values for trend from 0.06 to 0.01). Effect sizes were small, ranging between 0.03 and 0.05 difference in the standardized neurodevelopmental scores. Estimates for ART were imprecise, but there were no differences between children conceived by ART and naturally conceived children of subfecund parents (TTP ≥12 months). CONCLUSIONS: Longer parental TTP is modestly but robustly associated with offspring neurodevelopmental delays and difficulties, with no added impact of ART. Future studies should investigate the underlying causes of-or aspects related to-parental subfecundity which might explain the association with offspring neurodevelopmental delays and difficulties.

Medically Assisted Reproduction Treatment Types and Birth Outcomes: A Between-Family and Within-Family Analysis.

OBJECTIVE: To compare risks of adverse birth outcomes among pregnancies conceived with and without medically assisted reproduction treatments. METHODS: Birth certificates were used to study birth outcomes of all neonates born in Utah from 2009 through 2017. Of the 469,919 deliveries, 52.8% (N=248,013) were included in the sample, with 5.2% of the neonates conceived through medically assisted reproduction. The outcome measures included birth weight, gestational age, low birth weight (LBW, less than 2,500 g), preterm birth (less than 37 weeks of gestation), and small for gestational age (SGA, birth weight less than the 10th percentile). Linear models were estimated for the continuous outcomes (birth weight, gestational age), and linear probability models were used for the binary outcomes (LBW, preterm birth, SGA). First, we compared the birth outcomes of neonates born after medically assisted reproduction and natural conception in the overall sample (between-family analyses), before and after adjustment for parental background and neonatal characteristics. Second, we employed family fixed effect models to investigate whether the birth outcomes of neonates conceived through medically assisted reproduction differed from those of their naturally conceived siblings (within-family comparisons). RESULTS: Neonates conceived through medically assisted reproduction weighed less, were born earlier, and were more likely to be LBW, preterm, and SGA than neonates conceived naturally. More invasive treatments (assisted reproductive technology [ART] and artificial insemination [AI] or intrauterine insemination) were associated with worse birth outcomes; for example, the proportion of LBW and preterm birth was 6.1% and 7.9% among neonates conceived naturally and 25.5% and 29.8% among neonates conceived through ART, respectively. After adjustments for various neonatal and parental characteristics, the differences in birth outcomes between neonates conceived through medically assisted reproduction and naturally were attenuated yet remained statistically significant; for example, neonates conceived through ART were at 3.2 percentage points higher risk for LBW (95% CI 2.4-4.1) and 4.8 percentage points higher risk for preterm birth (95% CI 3.9-5.7). Among siblings, the differences in the frequency of adverse outcomes between neonates conceived through medically assisted reproduction and neonates conceived naturally were small and statistically insignificant for all types of treatments. CONCLUSION: Medically assisted reproduction treatments are associated with adverse birth outcomes; however, those risks are unlikely to be associated with the infertility treatments itself.

Sibling group size and BMI over the life course: Evidence from four British cohort studies.

Only children, here defined as individuals growing up without siblings, are a small but growing demographic subgroup. Existing research has consistently shown that, on average, only children have higher body mass index (BMI) than individuals who grow up with siblings. How this difference develops with age is unclear and existing evidence is inconclusive regarding the underlying mechanisms. We investigate BMI trajectories for only children and those with siblings up to late adolescence for four British birth cohorts and across adulthood for three cohorts. We use data on BMI from ages 2-63 years (cohort born 1946); 7-55 years (born 1958); 10-46 (born 1970) and 3-17 years (born 2000-2002). Using mixed effects regression separately for each cohort, we estimate the change in BMI by age comparing only children and those with siblings. The results show higher average BMI among only children in each cohort, yet the difference is substantively small and limited to school age and adolescence. The association between sibling status and BMI at age 10/11 is not explained by differential health behaviours (physical activity, inactivity and diet) or individual or family background characteristics in any of the cohorts. Although persistent across cohorts, and despite the underlying mechanism remaining unexplained, the substantively small magnitude of the observed difference and the convergence of the trajectories by early adulthood in all cohorts raises doubts about whether the difference in BMI between only children and siblings in the UK context should be of research or clinical concern. Future research could usefully be directed more at whether only children experience elevated rates of disease, for which high BMI is a risk factor, at different stages of the life course and across contexts.

The cognitive development from childhood to adolescence of low birthweight children born after medically assisted reproduction-a UK longitudinal cohort study.

BACKGROUND: Previous research has documented that children conceived through medically assisted reproduction (MAR) are at increased risk of poor birth outcomes, such as low birthweight (LBW), which are risk factors for stunted longer-term cognitive development. However, parents who undergo MAR to conceive have, on average, advantaged socioeconomic backgrounds which could compensate for the negative effects of being born LBW. Previous studies have not analysed whether the negative effects of LBW are attenuated among MAR conceived children. METHODS: We draw on the UK Millennium Cohort Study (sweeps 1-6) which contains a sub-sample of (N = 396) MAR-conceived children. The dependent variable measures cognitive ability at around ages 3, 5, 7, 11 and 14. We examine the cognitive development of four groups of children: MAR-conceived low birthweight (MAR LBW); MAR-conceived non-low birthweight (MAR NLBW); naturally conceived low birthweight (NC LBW); naturally conceived non-low birthweight (NC NLBW). We estimate the two following linear regression models for each sweep: (i) a baseline model to examine the unadjusted association between cognitive development and low birthweight by mode of conception; and (ii) a model adjusted by socio-demographic family characteristics. RESULTS: In baseline models, MAR LBW children [age 3: ß = 0.021, 95% confidence interval (CI): -0.198, 0.241; age 5: ß = 0.21, 95% CI: 0.009, 0.418; age 7: ß = 0.163, 95% CI: -0.148, 0.474; age 11: ß = 0.003, 95% CI: -0.318, 0.325; age 14: ß = 0.156, 95% CI: -0.205, 0.517], on average perform similarly in cognitive ability relative to NC NLBW at all ages, and display higher cognitive scores than NC LBW children until age 7. When we account for family characteristics, differences are largely attenuated and become close to zero at age 14. CONCLUSIONS: Despite the higher incidence of LBW among MAR compared with NC children, they do not seem to experience any disadvantage in their cognitive development compared with naturally conceived children. This finding is likely explained by the fact that, on average, MAR children are born to socioeconomically advantaged parents.