Implications of childhood adversity for women's perinatal sleep quality and depressive symptoms over time: A serial mediation model.

This study sought to examine the effects of childhood adversity on the longitudinal associations between perinatal sleep quality and depressive symptoms, and to determine the prospective associations between these constructs over time. A cross-lagged autoregressive model was used to examine the longitudinal association between sleep quality and depressive symptoms at four points during the perinatal period: 18 and 32 weeks of pregnancy, and 6 and 12 weeks postpartum. Longitudinal mediation models were used to examine whether sleep quality or depressive symptoms mediated the effects of childhood adversity on these symptoms. Most participants (86%) reported poor sleep quality during pregnancy. Significant cross-lagged effects of depressive symptoms on subsequent sleep quality were observed during pregnancy and postpartum. Depressive symptoms significantly mediated the effects of childhood trauma on sleep quality during pregnancy, but sleep quality did not significantly mediate the effects of childhood trauma on depressive symptoms. While sleep quality and depressive symptoms tend to co-occur, our analyses indicate that perinatal depressive symptoms work as the primary driver of sleep quality over time. Childhood adversity may have long-reaching effects in women as it was associated with more depressive symptoms in the perinatal period, which in turn appeared to undermine sleep quality.

Individual differences in processing speed and curiosity explain infant habituation and dishabituation performance.

Habituation and dishabituation are the most prevalent measures of infant cognitive functioning, and they have reliably been shown to predict later cognitive outcomes. Yet, the exact mechanisms underlying infant habituation and dishabituation are still unclear. To investigate them, we tested 106 8-month-old infants on a classic habituation task and a novel visual learning task. We used a hierarchical Bayesian model to identify individual differences in sustained attention, learning performance, processing speed and curiosity from the visual learning task. These factors were then related to habituation and dishabituation. We found that habituation time was related to individual differences in processing speed, while dishabituation was related to curiosity, but only for infants who did not habituate. These results offer novel insights in the mechanisms underlying habituation and serve as proof of concept for hierarchical models as an effective tool to measure individual differences in infant cognitive functioning. RESEARCH HIGHLIGHTS: We used a hierarchical Bayesian model to measure individual differences in infants' processing speed, learning performance, sustained attention, and curiosity. Faster processing speed was related to shorter habituation time. High curiosity was related to stronger dishabituation responses, but only for infants who did not habituate.

Prenatal anticipatory stress: Baby preparation and worry scale-revised in the Dutch context.

BACKGROUND: Prenatal distress encompasses a range of different emotions, worries, and experiences of stress. The Baby Preparation and Worry Scale (Baby-PAWS) was recently developed to target anticipatory worries during pregnancy about the postnatal period. However, the Baby-PAWS questionnaire was only examined in the United States of America, limiting the questionnaire's generalizability to different countries. To address this issue, we performed a psychometric evaluation of the questionnaire in a Dutch sample and examined associations between the Baby-PAWS questionnaire and established measures of maternal distress (i.e., EPDS, STAI, PRAQ-R) and infant temperament (i.e., IBQ-R). METHODS: Healthy pregnant women (N = 521) completed questionnaires during their third trimester and postnatally, including the Baby-PAWS and distress measures. A subsample of mothers (N = 194) also reported on infant temperament at 12 weeks postpartum. RESULTS: Exploratory factor analysis suggested a four-factor structure for the 16-item questionnaire in our Dutch sample, as compared to the expected three-factor structure found in the original psychometric evaluation with the American sample. The total Baby-PAWS score was related to pre-and postnatal depression, anxiety, stress, and specific scales of infant temperament. American women scored higher on the Baby-PAWS items than Dutch women. LIMITATIONS: Our participants had higher-than-average socioeconomic status, limiting the generalizability of the findings. CONCLUSION: The current analyses indicate good validity of the Baby-PAWS in a Dutch sample. Furthermore, our results highlight cross-cultural differences in perinatal mental health and show the importance of examining instrument structure of context-dependent constructs, such as prenatal worries.

Maternal early life and prenatal stress in relation to birth outcomes in Argentinian mothers.

Environmental influences before and during pregnancy significantly impact offspring development. This study investigates open research questions regarding the associations between maternal early life stress (ELS), prenatal psychosocial stress, prenatal hair cortisol (HC), and birth outcomes in Argentinian women. Data on ELS, prenatal life events, HC (two samples representing first and second half of pregnancy), and birth outcomes were collected from middle-class Argentinian women (N = 69) upon delivery. Linear mixed models indicated that HC increased from the first half to the second half of pregnancy with considerable variability in the starting values and slopes between individuals. Mothers who experienced more ELS, were taller, or more educated, tended to show lower increases in HC. Older age was positively related to HC increases. Our data did not suggest an interaction between ELS and prenatal life events in relation to HC. We found that the change in HC was most likely negatively associated with birth weight. Our data are most compatible with either a weak or the absence of an association between ELS or prenatal life events and absolute values of HC. Mothers with stronger increases in hair cortisol tended to have newborns with slightly lower birth weight. Hence, ELS and birthweight may either have been related to changes in cortisol exposure during pregnancy or to factors that influence accumulation or retention of cortisol in hair.

Development of the gut microbiota in the first 14 years of life and its relations to internalizing and externalizing difficulties and social anxiety during puberty.

Relations between the gut microbiota and host mental health have been suggested by a growing number of case-control and cross-sectional studies, while supporting evidence is limited in large community samples followed during an extended period. Therefore, the current preregistered study ( https://osf.io/8ymav , September 7, 2022) described child gut microbiota development in the first 14 years of life and explored its relations to internalizing and externalizing difficulties and social anxiety in puberty, a period of high relevance for the development of mental health problems. Fecal microbiota composition was analysed by 16S ribosomal RNA gene amplicon sequencing in a total of 1003 samples from 193 children. Through a clustering method, four distinct microbial clusters were newly identified in puberty. Most children within three of these clusters remained in the same clusters from the age of 12 to 14 years, suggesting stability in microbial development and transition during this period. These three clusters were compositionally similar to enterotypes (i.e., a robust classification of the gut microbiota based on its composition across different populations) enriched in Bacteroides, Prevotella, and Ruminococcus, respectively. Two Prevotella 9-predominated clusters, including one reported by us earlier in middle childhood and the other one in puberty, were associated with more externalizing behavior at age 14. One Faecalibacterium-depleted pubertal cluster was related to more social anxiety at age 14. This finding was confirmed by a negative cross-sectional relation between Faecalibacterium and social anxiety in the 14-year-olds. The findings of this study continue to map gut microbiota development in a relatively large community sample followed from birth onwards, importantly extending our knowledge to puberty. Results indicate that Prevotella 9 and Faecalibacterium may be relevant microbial taxa in relation to externalizing behavior and social anxiety, respectively. These correlational findings need validations from other similar cohort studies, as well as well-designed mechanistic pre-clinical investigations before inferring cause and effect.

Commentary: Natural disaster studies on prenatal stress - moving forward - a commentary/reflection on Nomura et al. (2023).

This commentary is based on the premise that the goal of scientific publications is to advance knowledge and inspire scientific discussion. First, the Nomura et al. paper is briefly summarized and shortly discussed to illustrate some of the challenges faced in this field, and suggestions for improvement are made. Then, the reader is invited to take a step back and reflect on how to continue investigating the effects of natural disasters on pregnant women and their children in the best possible manner. Additional suggestions are made for much-needed research on other types of severe maternal prenatal stress and on high-quality interventions for natural disasters. The goal is to stimulate reflection and exchange so that future choices made by researchers, funding bodies, and policymakers lead to substantial advances in the field of prenatal stress.

Effects of daily full-term infant skin-to-skin contact on behavior and cognition at age three - secondary outcomes of a randomized controlled trial.

BACKGROUND: Daily skin-to-skin contact (SSC) during early infancy fosters the long-term development of children born preterm. This is the first randomized controlled trial assessing the potential beneficial effects of daily SSC on executive functioning and socio-emotional behavior of children born full-term. Whether children of mothers who experienced prenatal stress and anxiety benefitted more from SSC was also explored. METHODS: Pregnant women (N = 116) were randomly assigned to a SSC or care-as-usual (CAU) condition. Women in the SSC condition were instructed to perform one hour of SSC daily from birth until postnatal week five. Prenatal stress was measured with questionnaires on general and pregnancy-specific stress and anxiety completed by the mothers in gestational week 37. At child age three, mothers filled in questionnaires on children's executive functioning, and externalizing and internalizing behavior. Analyses were performed in an intention-to-treat (ITT), per-protocol, and dose-response approach. Netherlands Trial Register: NL5591. RESULTS: In the ITT approach, fewer internalizing (95% CI = 0.11-1.00, U = 2148.50, r = .24, p = .001) and externalizing (95% CI = 0.04-2.62, t = 2.04, d = 0.38, p = .04) problems were reported in the SSC condition compared to the CAU condition. Multivariate analyses of variance did not show group differences on executive functioning. Additional analyses of covariance showed no moderations by maternal prenatal stress. CONCLUSIONS: Current findings indicate that early daily SSC in full-term infants may foster children's behavioral development. Future replications, including behavioral observations of child behavior to complement maternal reports, are warranted.

Human milk: From complex tailored nutrition to bioactive impact on child cognition and behavior.

Human milk is a highly complex liquid food tailor-made to match an infant's needs. Beyond documented positive effects of breastfeeding on infant and maternal health, there is increasing evidence that milk constituents also impact child neurodevelopment. Non-nutrient milk bioactives would contribute to the (long-term) development of child cognition and behavior, a process termed 'Lactocrine Programming'. In this review we discuss the current state of the field on human milk composition and its links with child cognitive and behavioral development. To promote state-of-the-art methodologies and designs that facilitate data pooling and meta-analytic endeavors, we present detailed recommendations and best practices for future studies. Finally, we determine important scientific gaps that need to be filled to advance the field, and discuss innovative directions for future research. Unveiling the mechanisms underlying the links between human milk and child cognition and behavior will deepen our understanding of the broad functions of this complex liquid food, as well as provide necessary information for designing future interventions.

Maternal sensitivity and child internalizing and externalizing behavior: a mediating role for glucocorticoid receptor gene (NR3C1) methylation?

The early caregiving environment can have lasting effects on child mental health. Animal models suggest that glucocorticoid receptor gene (NR3C1) DNA methylation plays a mediating role in linking more responsive caregiving to improved behavioral outcomes by its impact on the stress regulatory system. In this longitudinal study, we examined whether children's NR3C1 methylation levels mediate an effect of maternal sensitivity in infancy on levels of child internalizing and externalizing behavior in a community sample. Maternal sensitivity of 145 mothers was rated at infant age 5 weeks, 12 months, and 30 months by observing mother-infant interactions. Buccal DNA methylation was assessed in the same children at age 6 years and maternal-reported internalizing and externalizing behavior was assessed at age 6 and 10 years. Higher sensitivity at age 5 weeks significantly predicted lower DNA methylation levels at two NR3C1 CpG loci, although methylation levels at these loci did not mediate an effect of maternal sensitivity on levels of child internalizing and externalizing behavior. Overall, the study provides evidence that maternal sensitivity in early infancy is associated with DNA methylation levels at loci involved in stress regulation, but the significance of this finding for child mental health remains unclear.

A longitudinal study of the gut microbiota during the first three years of life: Links with problem behavior and executive functions at preschool age.

Early life is a sensitive period when microbiota-gut-brain interactions may have important impact on development. This study investigated the associations of the gut microbiota in the first three years of life (two, six, and 12 weeks, and one and three years) with problem behavior and executive functions in N = 64 three-year-old children. Higher relative abundance of Streptococcus at the age of two weeks, as well as its trajectory over time (including ages two, six and 12 weeks, and one and three years), was related to worse executive functions. Higher relative abundance of [Ruminococcus] torques group at the age of three years, as well as its trajectory from one to three years, was associated with less internalizing behavior. Besides, several robust age-specific associations were identified: higher Bifidobacterium relative abundance (age three years) was associated with more internalizing and externalizing issues; higher Blautia relative abundance (age three years) was linked to less internalizing behavior; and increased relative abundance of an unidentified Enterobacteriaceae genus (age two weeks) was related to more externalizing behavior. Our findings provide important longitudinal evidence that early-life gut microbiota may be linked to behavioral and cognitive development in low-risk children.

Are adolescent diet quality and emotional eating predicted by history of maternal caregiving quality and concurrent inhibitory control?

The risk for unhealthy eating behaviour, including poor diet quality and emotional eating, is heightened in adolescence and could result in profound and long-lasting psychological and physical implications. Caregiving quality and adolescents' regulatory skills, such as inhibitory control, may play an essential role in the development of adolescent eating behaviour. This preregistered study investigated whether maternal caregiving throughout the first 14 years of life predicts adolescent diet quality and emotional eating and whether potential associations are mediated by adolescents' inhibitory control. In this low-risk community cohort, maternal caregiving quality was observed at child ages five weeks, 12 months, 2.5, 10, and 14 years. At age 14, diet quality and emotional eating were assessed through self-report. Adolescent inhibitory control was assessed with three behavioural tasks and a maternal report. Mediation analyses were performed with structural equation modelling in R. No evidence was found for links between maternal caregiving quality and adolescent diet quality and emotional eating. Higher levels of adolescent inhibitory control predicted better adolescent diet quality. Longitudinal and experimental studies are needed to investigate directionality, and replication studies are needed in more representative samples (e.g. including high-risk families). Such studies will shed further light on potential links between the history of caregiving behaviour and adolescent regulatory and eating behaviour.

The PedBE clock accurately estimates DNA methylation age in pediatric buccal cells.

The development of biological markers of aging has primarily focused on adult samples. Epigenetic clocks are a promising tool for measuring biological age that show impressive accuracy across most tissues and age ranges. In adults, deviations from the DNA methylation (DNAm) age prediction are correlated with several age-related phenotypes, such as mortality and frailty. In children, however, fewer such associations have been made, possibly because DNAm changes are more dynamic in pediatric populations as compared to adults. To address this gap, we aimed to develop a highly accurate, noninvasive, biological measure of age specific to pediatric samples using buccal epithelial cell DNAm. We gathered 1,721 genome-wide DNAm profiles from 11 different cohorts of typically developing individuals aged 0 to 20 y old. Elastic net penalized regression was used to select 94 CpG sites from a training dataset (n = 1,032), with performance assessed in a separate test dataset (n = 689). DNAm at these 94 CpG sites was highly predictive of age in the test cohort (median absolute error = 0.35 y). The Pediatric-Buccal-Epigenetic (PedBE) clock was characterized in additional cohorts, showcasing the accuracy in longitudinal data, the performance in nonbuccal tissues and adult age ranges, and the association with obstetric outcomes. The PedBE tool for measuring biological age in children might help in understanding the environmental and contextual factors that shape the DNA methylome during child development, and how it, in turn, might relate to child health and disease.

Adolescents' hair cortisol concentrations during COVID-19: Evidence from two longitudinal studies in the Netherlands and the United States.

BACKGROUND: Prolonged stress exposure is associated with alterations in cortisol output. The COVID-19 pandemic represented a stressor for many, including children. However, a high-quality caregiving environment may protect against psychological problems and possibly against elevations in cortisol. We examined adolescents' physiological stress responses to the pandemic and the role of attachment in two longitudinal samples from the Netherlands and the United States (https://aspredicted.org/HHY_8MK). METHODS: Cortisol was assessed from hair samples before and during the pandemic, while attachment was self-reported prepandemic. Study 1 included a Dutch sample (N = 158; examined at ages 10 and later at 14 years old), whereas Study 2 included a US sample (N = 153; examined at ages 9-11 and again 2 years later) and an age-matched prepandemic sample (N = 29, 10-13 years old). Repeated-measures analyses of variance examined changes in cortisol from prepandemic to during the pandemic and the effect of attachment in each sample separately. RESULTS: After accounting for age, both studies revealed nonsignificant changes in hair cortisol and a nonsignificant effect of attachment. A significant effect of sex emerged in Study 1, with Dutch girls showing a significant cortisol increase during the pandemic, which was not explained by puberty. CONCLUSION: These findings suggest differential associations of the pandemic with hair cortisol increases by sex and country.

Maternal anxiety forecasts shorter prolongation of pregnancies complicated by early-onset preeclampsia.

PURPOSE: In early-onset preeclampsia, each additional day of pregnancy prolongation reduces offspring infant mortality about 9%. We evaluated if maternal stress at admission to hospital for early-onset preeclampsia predicted admission-to-delivery intervals in days. METHODS: This prospective, longitudinal cohort-study involved 15 singleton pregnancies with a diagnosis of preeclampsia before 34 weeks gestation with intended expectant management. Upon hospital admission, maternal psychological stress was assessed with questionnaires and physiological stress with hair cortisol. Hair samples were analyzed in three hair segments representing the preconception period, and the first and second trimester of pregnancy. RESULTS: Mean pregnancy prolongation was 16.2 days. Higher maternal anxiety at hospital admission significantly correlated with shorter admission-to-delivery intervals (r = - 0.54, p = 0.04). Chronically increased hair cortisol concentrations (i.e. from preconception through the second trimester) of pregnancy tended to be related to shorter admission-to-delivery intervals (p <. 10). CONCLUSION: Higher reported anxiety is, and chronically high hair cortisol tended to be, related with fewer days of prolongation from admission to delivery in women with early-onset preeclampsia. These findings suggest that maternal stress might be a potential determinant of disease progression. Future research into early innovative stress-reducing interventions for early-onset preeclampsia may shed more light on the etiology and treatment of this disease.

Cortisol and testosterone concentrations during the prenatal and postpartum period forecast later caregiving quality in mothers and fathers.

Given that parental caregiving quality affects child development from birth onwards, it is important to detect parents who are at risk for low-quality caregiving as early as possible, preferably before or soon after birth. This study investigated whether cortisol (CORT) and testosterone (T) measured during the last trimester of pregnancy and six weeks postpartum were associated with observed caregiving quality at child age 3 in mothers (N = 63) and fathers (N = 45). CORT and T were measured during an interaction with a simulator infant (pregnancy) and their own infant (postpartum). In mothers, no associations were found with CORT and T during pregnancy, but higher postpartum CORT during a mother-infant interaction was related to higher caregiving quality during toddlerhood. In fathers, the association between T during pregnancy and caregiving quality in toddlerhood was more negative for fathers with low CORT. In contrast to mothers, higher postpartum CORT in fathers was associated with lower caregiving quality in toddlerhood. These findings proved robust after applying the Benjamini-Hochberg procedure to control for false discovery rate. Our findings indicate that CORT and T during the perinatal period can forecast caregiving quality in both mothers and fathers. Moreover, our results provided evidence for the dual-hormone hypothesis, but only in fathers. These findings contribute to our growing understanding on how endocrine measures explain individual differences in caregiving quality in mothers and fathers.

Parents of young infants report poor mental health and more insensitive parenting during the first Covid-19 lockdown.

BACKGROUND: The Covid-19 pandemic has put an unprecedented pressure on families with children. How parents were affected by the first Covid-19 lockdown during the early postpartum period, an already challenging period for many, is unknown. AIM: To investigate the associations between Covid-19 related stress, mental health, and insensitive parenting practices in mothers and fathers with young infants during the first Dutch Covid-19 lockdown. METHODS: The Dutch Covid-19 and Perinatal Experiences (COPE-NL) study included 681 parents of infants between 0 and 6 months (572 mothers and 109 fathers). Parents filled out online questionnaires about Covid-19 related stress, mental health (i.e. anxiety and depressive symptoms), and insensitive parenting. Hierarchical regression models were used to analyze the data. RESULTS: Parents of a young infant reported high rates of Covid-19 related stress, with higher reported stress in mothers compared to fathers. Additionally, the percentages of mothers and fathers experiencing clinically meaningful mental health symptoms during the pandemic were relatively high (mothers: 39.7% anxiety, 14.5% depression; fathers: 37.6% anxiety, 6.4% depression). More Covid-19 related stress was associated with more mental health symptoms in parents and increased insensitive parenting practices in mothers. CONCLUSIONS: The results emphasize the strain of the pandemic on young fathers' and mothers' mental health and its potential negative consequences for parenting. As poor parental mental health and insensitive parenting practices carry risk for worse child outcomes across the lifespan, the mental health burden of the Covid-19 pandemic might not only have affected the parents, but also the next generation.

Can gut microbiota throughout the first 10 years of life predict executive functioning in childhood?

Animal models suggest that the gut microbiota can influence cognitive development and functioning via various pathways. In line with that, a first human study found associations between infant fecal microbiota composition and cognition at 2 years of age. This longitudinal study investigated whether fecal microbiota composition in infancy and childhood is associated with executive functioning in childhood. We followed healthy individuals from birth to their 10th year of life. Executive functioning was assessed using the Digit Span working memory test at 10 years of age and the ecologically valid Behavior Rating Inventory for executive functioning at 8 and 10 years. Stool samples were collected at month 1, 3 and 4 as well as at 6 and 10 years. The V4 region of the 16S ribosomal RNA was analyzed to determine microbial composition at the genus level. Using established statistical techniques for microbiota analysis, we did not find associations between fecal microbiota composition and executive functioning after accounting for breastfeeding, maternal education, child sex and age. Our study results are most compatible with the absence or only a weak relationship between infant and childhood fecal microbiota composition and executive functioning in childhood in healthy community children.

Effects of skin-to-skin contact on full-term infants' stress reactivity and quality of mother-infant interactions.

Skin-to-skin contact (SSC) between mothers and their infants has beneficial effects in both preterm and full-term infants. Underlying mechanisms are largely unknown. This randomized controlled trial assessed whether daily SSC in full-term mother-infant dyads: (1) decreases infants' cortisol and behavioral reactivity to a mild naturalistic stressor, and (2) facilitates interaction quality between infants and mothers (i.e., improved maternal caregiving behavior and mother-infant adrenocortical synchrony). Pregnant Dutch women (N = 116) were recruited and randomly allocated to an SSC or care-as-usual condition. The SSC condition performed 1 h of SSC daily, from birth until postnatal week 5. In week 5, mothers bathed the infant (known mild stressor). Infant and maternal cortisol was sampled at baseline, 25 and 40 min after bathing, and infant and maternal behavior was rated. Results did not indicate effects of SSC on infant behavioral and cortisol reactivity to the bathing session. Similarly, no effect of SSC was found on maternal caregiving behavior and mother-infant adrenocortical synchrony. In conclusion, the findings provide no evidence that daily mother-infant SSC is associated with full-term infants' behavioral and adrenocortical stress reactivity or mother-infant interaction quality. Future studies should replicate these findings and unveil other potential mechanisms underlying beneficial effects of SSC.

Can Maternal Prenatal Self-Reported and Physiological Distress Predict Postnatal Caregiving Practices?

Maternal prenatal distress is associated with child outcomes, including health, neurocognitive, and socio-emotional development. Knowledge on underlying mechanisms is limited, yet relevant for prevention and intervention. This study investigated whether maternal prenatal distress predicts specific caregiving practices that are known for their effects on child outcomes. Caregiving practices studied were maternal caregiving quality and the initiation and course of breastfeeding and room-sharing. We hypothesized that more maternal prenatal distress would be associated with altered caregiving practices. Participants were 174 healthy mother-child dyads. During the 37th week of pregnancy maternal self-reported distress was assessed using questionnaires, and physiological stress by collecting saliva cortisol. Maternal caregiving quality was observed in postnatal week 5 during infant bathing. Weekly diaries on breastfeeding and daily diaries on room-sharing were completed during the first 6 postnatal months. In a regression analysis, no associations between maternal prenatal distress and caregiving quality were found. Multilevel analyses indicated that maternal prenatal evening cortisol was positively related to the initiation of breastfeeding and room-sharing. Replications are warranted, but these results suggest that breastfeeding and room-sharing initiation may be part of a mechanism underlying links between maternal prenatal physiological stress and child outcomes. As other prenatal cortisol markers and self-reported distress were not found to be related to the caregiving practices, it is likely that alternative mechanisms (co-)exist in explaining links between maternal prenatal distress and child outcomes. Future replication research including child outcomes and (other) potential mechanisms will inform prevention and intervention programs fostering healthy pregnancies and child development.

Daily skin-to-skin contact in full-term infants and breastfeeding: Secondary outcomes from a randomized controlled trial.

This randomized controlled trial evaluated the effect of a 5-week daily skin-to-skin contact (SSC) intervention between mothers and their full-term infants, compared with care-as-usual, on exclusive and continued breastfeeding duration during the first post-natal year. Healthy pregnant women (n = 116) from a community sample were enrolled and randomly allocated to the SSC or care-as-usual condition. SSC mothers were requested to provide one daily hour of SSC for the first five post-natal weeks. Twelve months post-partum, mothers indicated the number of exclusive and continued breastfeeding months. Multiple regression analyses were conducted using intention-to-treat, per-protocol and exploratory dose-response frameworks. In intention-to-treat analyses, exclusive and continued breastfeeding duration was not different between groups (exclusive: 3.61 ± 1.99 vs. 3.16 ± 1.77 months; adjusted mean difference 0.28, 95% confidence interval [CI] -0.33 to 0.89; p = 0.36; continued: 7.98 ± 4.20 vs. 6.75 ± 4.06 months; adjusted mean difference 0.81, 95% CI -0.46 to 2.08; p = 0.21). In per-protocol analyses, exclusive and continued breastfeeding duration was longer for SSC than care-as-usual dyads (exclusive: 4.89 ± 1.26 vs. 3.25 ± 1.80 months; adjusted mean difference 1.28, 95% CI 0.31-2.24; p = 0.01; continued: 10.81 ± 1.97 vs. 6.98 ± 4.08 months; adjusted mean difference 2.33, 95% CI 0.13-4.54; p = 0.04). Exploratory dose-response effects indicated that more SSC hours predicted longer exclusive and continued breastfeeding duration. This study demonstrates that for the total group, the 5-week daily SSC intervention did not extend exclusive and continued breastfeeding duration. However, for mothers performing a regular daily hour of SSC, this simple and accessible intervention may extend exclusive and continued breastfeeding duration by months. Future studies are required to confirm these promising findings. Trial registration: Netherlands Trial Register (NTR5697).