Expectant Mothers Maximizing Opportunities: Maternal Characteristics Moderate Multifactorial Prenatal Stress in the Prediction of Birth Weight in a Sample of Children Adopted at Birth

<div><p>Background</p><p>Mothers’ stress in pregnancy is considered an environmental risk factor in child development. Multiple stressors may combine to increase risk, and maternal personal characteristics may offset the effects of stress. This study aimed to test the effect of 1) multifactorial prenatal stress, integrating objective “stressors” and subjective “distress” and 2) the moderating effects of maternal characteristics (perceived social support, self-esteem and specific personality traits) on infant birthweight.</p><p>Method</p><p>Hierarchical regression modeling was used to examine cross-sectional data on 403 birth mothers and their newborns from an adoption study.</p><p>Results</p><p>Distress during pregnancy showed a statistically significant association with birthweight (R² = 0.032, <i>F</i>_{(2, 398)} = 6.782, <i>p</i> = .001). The hierarchical regression model revealed an almost two-fold increase in variance of birthweight predicted by stressors as compared with distress measures (R²<i>Δ</i> = 0.049, <i>F</i>_{(4, 394)} = 5.339, <i>p</i> < .001). Further, maternal characteristics moderated this association (R²<i>Δ</i> = 0.031, <i>F</i>_{(4, 389)} = 3.413, <i>p</i> = .009). Specifically, the expected benefit to birthweight as a function of higher SES was observed only for mothers with lower levels of harm-avoidance and higher levels of perceived social support. Importantly, the results were not better explained by prematurity, pregnancy complications, exposure to drugs, alcohol or environmental toxins.</p><p>Conclusions</p><p>The findings support multidimensional theoretical models of prenatal stress. Although both objective stressors and subjectively measured distress predict birthweight, they should be considered distinct and cumulative components of stress. This study further highlights that jointly considering risk factors and protective factors in pregnancy improves the ability to predict birthweight.</p></div

Summary of hierarchical regression predicting child birthweight from birth mother distress, stressors and protective maternal characteristics in full term infants only.

<p><i>Note</i>. All variables (except interaction terms) were standardized before being entered into the regression model. MW = Material Worry, NLE = Negative life events, SES = Socio-economic Status, CFS = Chronic Family Stress, RC = Relational conflict.</p><p>^α<i>p</i> < .1</p><p>*<i>p</i> < .05</p><p>**<i>p</i> < .01</p><p>Summary of hierarchical regression predicting child birthweight from birth mother distress, stressors and protective maternal characteristics in full term infants only.</p

Model of multiple factors contributing to prenatal stress, maternal characteristics and birthweight.

<p>Model of multiple factors contributing to prenatal stress, maternal characteristics and birthweight.</p

Descriptive statistics for Birth mothers (<i>N</i> = 403).

<p><i>Note</i>. All final scales included in the study were standardized prior to data analysis</p><p>(<i>M</i> = 0, <i>SD</i> = 1).</p><p>^a Based on standardized scores</p><p>BW = Birthweight, PRI = Pregnancy Risk Index, NLE = Negative life events, SES = Socio-economic Status, CFS = Chronic Family Stress, RC = Relational conflict, MW = Material Worry</p><p>Descriptive statistics for Birth mothers (<i>N</i> = 403).</p

Interaction between socio-economic status and maternal characteristics in predicting birthweight plotted at the mean, 1 SD above and 1SD below the mean on maternal characteristics scale.

<p>Interaction between socio-economic status and maternal characteristics in predicting birthweight plotted at the mean, 1 SD above and 1SD below the mean on maternal characteristics scale.</p

Sample demographics.

<p>Sample demographics.</p

Percentage of reported asthma and breathlessness, register based asthma diagnosis and medication by level of reported maternal anxiety in a cross-sectional twin study.

1<p>Maternal anxiety assessed with BAI was only available for study 2.</p>2<p>Breathlessness reported by child was only available for study 2.</p>3<p>At least two purchases of asthma medication, except oral beta-2-agonists, on different days July 2005– December 2009.</p

Descriptive data of the study population.

<p>NA = not available, i.e. questions not included in the questionnaire, Q₁ = 1^st quartile, Q₃ = 3^rd quartile.</p>1<p>Not available for pregnancies before 1982.</p>A<p>Same sex female twin pairs born 1926–1966.</p>B<p>Same sex female and male twin pairs born 1944–1971.</p>C<p>Each twin was living together with a partner in a long-term relationship. The adolescent child was 11–22 years old and was living together with the parents. The cousins were the same sex and not more than 4 years apart in age.</p

Table of inter-correlations final set of study variables of birth mothers and birthweight (<i>N</i> = 403).

<p><i>Note</i>. BW = Birthweight, PRI = Pregnancy Risk Index, NLE = Negative Life Events, SES = Socio-economic Status, CFS = Chronic Family Stress, RC = Relational Conflict, MW = Material Worry.</p><p>*<i>p</i> < .05</p><p>**<i>p</i> < .01.</p><p>Table of inter-correlations final set of study variables of birth mothers and birthweight (<i>N</i> = 403).</p

Crude and adjusted analyses of association between level of maternal anxiety and offspring asthma as reported in questionnaires and recorded in registers.

1<p>Maternal anxiety assessed with BAI was only available for study 2.</p>2<p>Breathlessness reported by child was only available for study 2.</p>3<p>At least two purchases of asthma medication, except oral beta-2-agonists, on different days July 2005– December 2009.</p>4<p>Adjusted for mother’s education, maternal smoking at time of the study, maternal asthma, sex and age of the child, preterm birth, birth weight and caesarean section.</p>5<p>Sample sizes for crude/adjusted analyses.</p