Intensive Parenting: Fertility and Breastfeeding Duration in the United States

Best for Whom? Heterogeneous Treatment Effects of Breastfeeding on Child Development

The slogan "Breast is Best" has been popularized by medical organizations and parenting networks to extoll the benefits of breastfeeding, yet the causal effects are widely debated. Our study contributes to the debate by examining whether breastfeeding has differential effects based on the propensity to breastfeed, which is also known as causal effect heterogeneity. Prior studies attempt to isolate the causal effect of breastfeeding by netting out confounding characteristics, but we argue that the effects of breastmilk are unlikely to operate in a vacuum. The social forces that promote or constrain breastfeeding among different populations in American society can also shape its effects. Using rich intergenerational panel data from the NLSY79 Child and Young Adult cohort (n = 7902), we evaluate heterogeneous treatment effects in the relationship between breastfeeding and child development from ages 4 to 14 using stratification-multilevel propensity score models. We find that breastfeeding is associated with small benefits for behavioral development, math scores, and academic ability among those with the highest propensities to breastfeed. By contrast, its small benefits for reading comprehension and vocabulary are concentrated among children with the lowest propensities to breastfeed. Our findings suggest that the social process of selection into breastfeeding cannot be fully disentangled from its estimated effects. The social context not only shapes who breastfeeds in American society, but also who benefits most.

How do reproduction, parenting, and health cluster together? Exploring diverging destinies, life histories and weathering in two UK cohort studies

Life history theory researchers often assume reproductive, parenting and health behaviours pattern across a fast-slow continuum, with 'fast' life histories (typified by short lifespans, early maturation and investing in quantity over quality of children) favoured in poor quality environments and/or when resources are scarce. Some researchers further reduce this down to a simplistic 'fast' versus 'slow' dichotomy. Some of these ideas, with different theoretical motivations, are echoed in the 'diverging destinies' and 'weathering' frameworks developed in the social sciences. Whether clustering of reproductive, parenting and health traits exists has rarely been empirically tested, however. Using latent class analysis on data on mothers from the UK's Millennium Cohort (MCS) and Born in Bradford (BiB) studies, we explored whether reproduction and parenting traits clustered into 'diverging destinies', whether 'weathering' effects tied together health and reproduction, and whether all three domains were combined into either 'fast' vs 'slow' life histories, or into three groups more indicative of a fast-slow continuum. We leveraged ethnic diversity in these samples to examine four groups of mothers separately: 1. MCS White British/Irish (n = 15,423); 2. MCS Pakistani-origin (n = 923); 3. BiB White British (n = 3937); 4. BiB Pakistani-origin (n = 4351), and explored whether faster 'weathering' was evident amongst Pakistani-origin mothers. Both two and three class models emerged as potential descriptions of latent subgroups, potentially providing support for fast and slow life histories or a continuum of traits. However, response profiles provided only limited support for theoretical predictions of which traits should cluster together, with inconsistent and restricted clustering of traits both within and between the domains of reproduction, parenting, and health. In addition, trait clustering was more pronounced amongst White mothers and we found no clear evidence supporting faster 'weathering' amongst Pakistani-origin mothers; the observed clustering instead suggested that cultural constraints may influence linkages between traits. Our results therefore provide some limited support for models which suggest certain traits cluster together in predictable ways, but it is also clear that theoretical frameworks should not emphasise very rigid clustering of large numbers of traits and should allow for contextual influences on clustering.

Assessing weaning stress - Relations between enamel hypoplasia, δ18O and δ13C values in human teeth obtained from early modern cemeteries in Wroclaw, Poland

OBJECTIVES

The aim of this paper is to assess linear enamel hypoplasia (LEH) on canines of adults from early modern Wroclaw cemeteries to compare δ¹³C and δ¹⁸O values in enamel formed before, during and after LEH formation, and to attempt to find a link between the selected indicators of the weaning process.

MATERIAL AND METHODS

15 permanent canines with visible LEH were selected for analysis. Age at LEH formation was estimated using the Reid and Dean method. The perikymata count was used to estimate the duration of LEH formation. Incremental stable oxygen and carbon isotopes analysis was performed on tooth enamel to infer stress related to weaning and dietary patterns. Kruskal-Wallis ANOVA, Mann-Whitney U test and Spearman correlation were used in statistical inference.

RESULTS

The average age of LEH formation was 3.14 years, with an average duration of 111 days. Stable carbon isotope values consistently increase in 73% of the individuals sampled. The values of δ¹⁸O do not show a dominant pattern. The average value of δ¹³C increases over the time of enamel formation. The δ¹³C values collected below LEH were negatively correlated with δ¹⁸O values and the duration of LEH termination.

CONCLUSIONS

Marking of carbon and oxygen isotopes indicates different stages of weaning. Advancements in diet change (determined by higher δ¹³C) corresponds with faster recovery after physiological stress episode. There is no evidence for different breastfeeding models between distinct parishes in early modern Wroclaw.

The association between breastfeeding and attachment: A systematic review

OBJECTIVE

In the popular and scientific literature an association between breastfeeding and attachment is often supposed although this has not been systematically investigated. This is the first review that provides a systematic overview of the current state of research on the association between breastfeeding and attachment. The objective is to determine whether breastfeeding is associated with child attachment as well as if maternal attachment is associated with breastfeeding behaviour.

DESIGN

A systematic electronic literature search for English language articles published from 1963 to 2019 using the databases Web of Science, PubMed, PsycInfo, and PsycArticles was conducted. Studies were included if (1) the association between breastfeeding and attachment of the child or maternal attachment style and breastfeeding was investigated, (2) participants were mothers or mother-child dyads, and (3) quantitative measures of breastfeeding and attachment were used. Study quality was rated using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies.

PARTICIPANTS

Studies examining mothers or mother-child dyads were reviewed. Sample sizes varied between N = 60 and N = 8900 participants. On average, mothers were between 27.56 and 32.50 years old.

FINDINGS

Eleven studies were eligible for inclusion. Of seven studies examining breastfeeding and child attachment, four found that a longer duration of breastfeeding was significantly associated with higher levels of attachment security after controlling for various covariates. No significant differences in attachment security between breastfeeding and bottle-feeding were reported, but one study found higher levels of attachment disorganization for bottle-feeding, although mean levels were below a clinically relevant level. The initiation of breastfeeding directly after childbirth was not related to child attachment. Of four studies examining maternal attachment and breastfeeding, three found a significant association between secure attachment of the mother and breastfeeding behaviour. Secure attached mothers initiated breastfeeding more often and preferred breast- over bottle-feeding than insecure attached mothers. Mixed results were found for breastfeeding duration. Most studies had limitations regarding adequate sample size, and valid and reliable measurement of breastfeeding.

KEY CONCLUSIONS

The findings provide some evidence that breastfeeding might contribute to child attachment security. Furthermore, maternal attachment style might play a role in breastfeeding behaviour. However, more prospective studies are needed to draw a solid conclusion.

IMPLICATIONS FOR PRACTICE

With regard to breastfeeding recommendations, health professionals should be aware of and communicate towards clients that the effect of breastfeeding on child attachment might be rather small. Screening of maternal attachment style as a part of maternity practice could be useful to support insecure attached mothers experiencing breastfeeding difficulties.