Secular changes in the association between advanced maternal age and the risk of low birth weight: A cross-cohort comparison in the UK

Unplanned births and their effects on maternal Health: Findings from the Constances Cohort

Unplanned births remain relatively common, even in regions with high contraceptive prevalence and accessible abortion services, such as contemporary France. Previous studies have shown that unplanned births can have numerous negative consequences for the well-being of mothers and children, including poorer maternal health behaviors, delayed and insufficient prenatal care, and depression during or immediately after pregnancy. However, these studies do not provide conclusive evidence on whether the observed outcomes are a consequence of unplanned births or of the conditions in which they likely occur. Furthermore, scant attention has been given to other dimensions of maternal well-being, such as physical health. This study uses longitudinal data from the French Constances Cohort and applies fixed-effects event study models to examine how women's self-rated general health and risk of depressive symptoms are affected in the years following an unplanned birth. Results show that women who had an unplanned birth reported a sudden, significant drop in their general health in the year following the birth, particularly among the youngest, while health outcomes following planned births showed a gradual, slight decrease over the time-period considered. The risk of depressive symptoms increased similarly after birth for both unplanned and planned births. This study contributes to the literature by using a longitudinally constructed measure of unplanned births based on pre-birth fertility intentions, rather than commonly used retrospective measures prone to ex post rationalization. It also distinguishes between unwanted and mistimed births while further examining their consequences on medium-term maternal health.

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.

Effect of medically assisted reproduction (MAR) and pregnancy planning on Bayley-III Screening Test subscales in preterm infants at 12 months of corrected age: a cross-sectional study

Background

The association between medically assisted reproduction and pregnancy planning on overall developmental outcomes of infants has been studied in relatively few studies. The availability of accurate tools for the early detection of developmental delays is a major issue. The purpose of this study is describing the average neurodevelopment of preterm infants and assessing the association between medically assisted reproduction, pregnancy planning and neurodevelopmental outcomes among Hungarian preterm infants.

Methods

Cross-sectional study of preterm infants with gestational age < 37 weeks (N = 171) who underwent developmental assessment using Bayley-III Screening Test (Bayley Scales of Infant and Toddler Development Screening Test – Third Edition) in five developmental domains (cognitive, receptive and expressive language, fine and gross motor) at 12 months of corrected age. We examined the developmental pattern of infants and the potential associations between medically assisted reproduction, pregnancy planning and Bayley-III Screening Test subscales. Information on the mode of conception and pregnancy planning was obtained through parental anamnesis.

Results

Concerning the risk for developmental delay, the language and motor subscales were the most affected. Examination of the mode of conception and developmental outcomes revealed higher neurodevelopmental skills in infants who were conceived through medically assisted reproduction. Significantly lower cognitive, receptive and expressive language skills were found to be associated with unplanned pregnancies. Multi-way analysis of variance was conducted in order to assess the impact of the mode of conception and pregnancy planning on subscales.

Conclusions

We cannot unambiguously conclude that MAR and pregnancy planning had a solely positive effect on the development of preterm infants at 12 months of corrected age, but our results are vital for the design and implementation of further research.

Effects of advanced maternal age and acute prenatal alcohol exposure on mouse offspring growth and craniofacial phenotype

BACKGROUND

Prenatal alcohol exposure (PAE) can result in developmental defects that include growth restriction, craniofacial anomalies, and cognitive behavioral deficits, though the presence and severity of these adverse outcomes can vary dramatically among exposed individuals. Preclinical animal models have demonstrated that the dose and timing of PAE account for much, but not all, of this phenotypic variation, suggesting that additional factors mitigate the effects of PAE. Here, we used a mouse model to investigate whether maternal age modulates the effects of PAE on the severity and variation in offspring growth and craniofacial outcomes.

METHODS

Nulliparous C57BL/6N dams received either an intraperitoneal injection of ethanol (EtOH) or vehicle solution on gestational day 7.5. Dams were divided into four groups: (1) EtOH-treated young dams (6 to 10 weeks); (2) control young dams; (3) EtOH-treated old dams (6 to 7 months); and (4) old control dams. Neonate offspring growth restriction was measured through body mass and organ-to-body mass ratios, while skeletal craniofacial features were imaged using micro-CT and analyzed for size, shape, and variation.

RESULTS

PAE and advanced maternal age each increased the risk of low birthweight and growth restriction in offspring, but these factors in combination changed the nature of the growth restriction. Similarly, both PAE and advanced maternal age individually caused changes to craniofacial morphology such as smaller skull size, dysmorphic skull shape, and greater skull shape variation and asymmetry. Interestingly, while the combination of PAE and advanced maternal age did not affect mean skull shape or size, it significantly increased the variation and asymmetry of those measures.

CONCLUSION

Our results indicate that maternal age modulates the effects of PAE, but that the effects of this combination on offspring outcomes are more complex than simply scaling the effects of either factor.

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: β  =  0.021, 95% confidence interval (CI): -0.198, 0.241; age 5: β  =  0.21, 95% CI: 0.009, 0.418; age 7: β  =  0.163, 95% CI: -0.148, 0.474; age 11: β  =  0.003, 95% CI: -0.318, 0.325; age 14: β  =  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.

Advanced maternal age and risk of adverse perinatal outcome among women with congenital heart disease: A nationwide register-based cohort study

BACKGROUND

Women with maternal congenital heart disease have a higher risk of preterm birth (PTB) and giving birth to a small for gestational age (SGA) infant. Advanced maternal age (≥35 years) likewise increases the risk of PTB and SGA, probably explained by poorer cardiovascular status. It is likely that advanced maternal age is particularly detrimental in women with congenital heart disease.

OBJECTIVES

We aimed to determine whether the pattern of higher risk of PTB and SGA with higher maternal age varied among women with and without congenital heart disease. We hypothesised that the effect of age is higher among women with congenital heart disease.

METHODS

We did a cohort study using Danish nationwide registers. Births from 1997 to 2014 were included. Cox regressions were used to estimate hazard ratios (HRs) for PTB and SGA. Universal and congenital heart disease-specific references were used for comparison.

RESULTS

We included 932 772 births among 548 314 women. HRs of PTB and SGA were 1.55 (95% confidence interval [CI] 1.37, 1.77) and 1.43 (95% CI 1.29, 1.58) in women with congenital heart disease as compared to women without. For both PTB and SGA, HRs were higher for women ≥35 years as compared to women aged 25-29 years. HRs of PTB and SGA were higher among women with congenital heart disease within all strata of maternal age as compared to women without (eg 3.71, 95% CI 1.80, 7.63 vs 1.63, 95% CI 1.56, 1.70) for SGA for women aged 40-44 years). The pattern of higher risk of PTB and SGA with higher maternal age was, however, similar among women with and without congenital heart disease.

CONCLUSIONS

Women with congenital heart disease had a higher risk of PTB and giving birth to an SGA infant at all maternal ages. These two risk factors did not, however, seem to potentiate each other.

Latest-Late Fertility? Decline and Resurgence of Late Parenthood Across the Low-Fertility Countries

After decades of fertility postponement, we investigate recent changes in late parenthood across low-fertility countries in the light of observations from the past. We use long series of age-specific fertility rates from the Human Fertility Database (1950-2016) for women, and new data covering the period 1990-2016 for men. In 1950, the contribution of births at age 40 and over to female fertility rates ranged from 2.5 to 9 percent, but then fell sharply until the 1980s. From the 1990s, however, the prevalence of late first births increased rapidly, especially so in countries where it was initially lowest. This has produced a late fertility rebound in the last two decades, occurring much faster for women than for men. Comparisons between recent and past extremely late (age 48+) fertility levels confirm that people are now challenging the natural fertility barriers, particularly for a first child.

Declining realisation of reproductive intentions with age

STUDY QUESTION

What is the likelihood of having a child within 4 years for men and women with strong short-term reproductive intentions, and how is it affected by age?

SUMMARY ANSWER

For women, the likelihood of realising reproductive intentions decreased steeply from age 35: the effect of age was weak and not significant for men.

WHAT IS KNOWN ALREADY

Men and women are postponing childbearing until later ages. For women, this trend is associated with a higher risk that childbearing plans will not be realised due to increased levels of infertility and pregnancy complications.

STUDY DESIGN, SIZE, DURATION

This study analyses two waves of the nationally representative Household, Income and Labour Dynamics in Australia (HILDA) survey. The analytical sample interviewed in 2011 included 447 men aged 18–45 and 528 women aged 18–41. These respondents expressed a strong intention to have a child in the next 3 years. We followed them up in 2015 to track whether their reproductive intention was achieved or revised.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Multinomial logistic regression is used to account for the three possible outcomes: (i) having a child, (ii) not having a child but still intending to have one in the future and (iii) not having a child and no longer intending to have one. We analyse how age, parity, partnership status, education, perceived ability to conceive, self-rated health, BMI and smoking status are related to realising or changing reproductive intentions.

MAIN RESULTS AND THE ROLE OF CHANCE

Almost two-thirds of men and women realised their strong short-term fertility plans within 4 years. There was a steep age-related decline in realising reproductive intentions for women in their mid- and late-30s, whereas men maintained a relatively high probability of having the child they intended until age 45. Women aged 38–41 who planned to have a child were the most likely to change their plan within 4 years. The probability of realising reproductive intention was highest for married and highly educated men and women and for those with one child.

LIMITATIONS, REASONS FOR CAUTION

Our study cannot separate biological, social and cultural reasons for not realising reproductive intentions. Men and women adjust their intentions in response to their actual circumstances, but also in line with their perceived ability to have a child or under the influence of broader social norms on reproductive age.

WIDER IMPLICATIONS OF THE FINDINGS

Our results give a new perspective on the ability of men and women to realise their reproductive plans in the context of childbearing postponement. They confirm the inequality in the individual consequences of delayed reproduction between men and women. They inform medical practitioners and counsellors about the complex biological, social and normative barriers to reproduction among women at higher childbearing ages.

STUDY FUNDING/COMPETING INTEREST(S)

This research was partly supported by a Research School of Social Sciences Visiting Fellowship at the Australian National University and an Australian Research Council Discovery Project (DP150104248). Éva Beaujouan’s work was partly funded by the Austrian Science Fund (FWF) project ‘Later Fertility in Europe’ (Grant agreement no. P31171-G29). This paper uses unit record data from the HILDA Survey. The HILDA Project was initiated and is funded by the Australian Government Department of Social Services (DSS) and is managed by the Melbourne Institute of Applied Economic and Social Research (Melbourne Institute). The findings and views reported in this paper, however, are those of the authors and should not be attributed to either DSS or the Melbourne Institute. The authors have no conflicts of interest.

Birth prevalence of Down syndrome in Argentina

The aim of this study was to describe the prevalence at birth of Down syndrome in Argentina. The prevalence by jurisdiction and maternal age was calculated for the 2009-2015 period and the prevalence and proportion of prenatal diagnosis was compared according to sub-sector (public and private) and complexity level of the maternity wards. The association of Down syndrome with birth weight and gestational age was analyzed. The data source was the National Network of Congenital Anomalies of Argentina [Red Nacional de Anomalías Congénitas] (RENAC). The prevalence was 17.26 per 10,000 births; by jurisdictions it varied between 10.99 and 23.71; and by maternal age, between 10.32 in women <20 years of age and 158.06 in those ≥45 years of age. In hospitals of the private subsector there was a higher prevalence, attributable to differences in the structure of maternal age, and a greater proportion of prenatal diagnosis. There was a negative correlation between birth weight and Down syndrome (ß=-294.7; p<0.001). No difference in the median gestational age at birth between Down syndrome newborns and newborns without major anomalies was found, but the distribution of gestational age differed. Knowledge of certain epidemiological characteristics of this health issue could contribute to the implementation of health policies.

Medically assisted reproduction and birth outcomes: a within-family analysis using Finnish population registers

BACKGROUND

Children born after medically assisted reproduction are at higher risk of adverse birth outcomes than are children conceived naturally. We aimed to establish the extent to which this excess risk should be attributed to harmful effects of treatment or to pre-existing parental characteristics that confound the association.

METHODS

We used data from Finnish administrative registers covering a 20% random sample of households with at least one child aged 0-14 years at the end of 2000 (n=65 723). We analysed birthweight, gestational age, risk of low birthweight, and risk of preterm birth among children conceived both by medically assisted reproduction and naturally. First, we estimated differences in birth outcomes by mode of conception in the general population, using standard multivariate methods that controlled for observed factors (eg, multiple birth, birth order, and parental sociodemographic characteristics). Second, we used a sibling-comparison approach that has not been used before in medically assisted reproduction research. We compared children conceived by medically assisted reproduction with siblings conceived naturally and, thus, controlled for all observed and unobserved factors shared by siblings.

FINDINGS

Between 1995 and 2000, 2776 (4%) children in our sample were conceived by medically assisted reproduction; 1245 children were included in the sibling comparison. Children conceived by medically assisted reproduction had worse outcomes than did those conceived naturally, for all outcomes, even after adjustments for observed child and parental characteristics-eg, difference in birthweight of -60 g (95% CI -86 to -34) and 2·15 percentage point (95% CI 1·07 to 3·24) increased risk of preterm delivery. In the sibling comparison, the gap in birth outcomes was attenuated, such that the relation between medically assisted reproduction and adverse birth outcomes was statistically and substantively weak for all outcomes-eg, difference in birthweight of -31 g (95% CI -85 to 22) and 1·56 percentage point (95% CI -1·26 to 4·38) increased risk of preterm delivery.

INTERPRETATION

Children conceived by medically assisted reproduction face an elevated risk of adverse birth outcomes. However, our results indicate that this increased risk is largely attributable to factors other than the medically assisted reproduction treatment itself.

FUNDING

European Research Council, the Academy of Finland, and the Signe and Ane Gyllenberg Foundation.

Advantages of later motherhood

BACKGROUND

In high-income countries childbearing has been increasingly postponed since the 1970s and it is crucial to understand the consequences of this demographic shift. The literature has tended to characterize later motherhood as a significant health threat for children and parents.

OBJECTIVES

We contribute to this debate by reviewing recent evidence suggesting that an older maternal age can also have positive effects.

MATERIALS

Literature linking the age at parenthood with the sociodemographic characteristics of the parents, with macrolevel interactions, and with subjective well-being.

METHODS

Comprehensive review of the existing literature.

RESULTS

Recent studies show that there can also be advantages associated with later motherhood. First, whilst in past older mothers had low levels of education and large families, currently older mothers tend to have higher education and smaller families than their younger peers. Consequently, children born to older mothers in the past tended to have worse outcomes than children born to younger mothers, whilst the opposite is true in recent cohorts. Second, postponement of childbearing means that the child is born at a later date and in a later birth cohort, and may benefit from secular changes in the macroenvironment. Evidence shows that when the positive trends in the macroenvironment are strong they overweigh the negative effects of reproductive ageing. Third, existing studies show that happiness increases around and after childbirth among older mothers, whereas for younger mothers the effect does not exist or is short-lived.

CONCLUSION

There are important sociodemographic pathways associated with postponement of childbearing which might compensate or even more than compensate for the biological disadvantages associated with reproductive ageing.