Birthweight and gestational age by ethnic group, England and Wales 2005: introducing new data on births

Low birthweight babies and babies born preterm are at increased risk of morbidity and mortality in the first year of life, as well as in the longer-term. Since information on ethnic group is not recorded at birth registration in England and Wales, it has not been possible to produce routine statistics on birthweight or gestational age by ethnic group. A new system, introduced in 2002, for allocating NHS numbers at birth (NN4B) provided the opportunity to obtain ethnic group information. The NN4B record includes information on the ethnic group of the baby classified according to the 2001 Census categories. This paper presents the first analyses of ethnic differences in birthweight and gestational age at birth for England and Wales as a whole. Utilising NN4B records linked with birth registration records for all births occurring in England and Wales in 2005, birthweight and gestational age distributions, including the percentages low birthweight and preterm, are compared between ethnic groups. The paper also examines how parental socio-demographic circumstances vary by ethnic group.     

Physical and behavioral sequelae of low birthweight in spiny mice (Acomys cahirinus)

Physical and behavioral sequelae of low birthweight (LBW) were investigated in spiny mice (Acomys cahirinus). When raised by their biological mother, pups whose Day-2 weights were 1 SD or more below the population mean remained smaller through the first 30 days postpartum than pups born within normal (N) weight ranges. LBW pups fostered onto mothers who gave birth to N pups gained weight more rapidly than LBW pups remaining with their own mother. Similarly, N pups fostered onto mothers of LBW pups displayed reduced weight gain relative to N siblings raised by their biological mother. It appears that rate of weight gain is influenced by an interaction between birthweight and maternal rearing environment. LBW pups also were less responsive than N pups to maternal chemical cues, indicating that low birthweight is correlated with deficits in adaptive behavior.     

Factors affecting birthweight of rural Australian Aborigines

AIM: To examine factors affecting birthweight of Aboriginal infants in the Kimberley region of north-west Australia. Research design: A retrospective study of maternal and infant health records obtained through routine data collection. Subjects and methods: Birthweight and length of 2959 infants born to 1822 women from 1986 to 1994 were analysed. Mothers and infants were matched using unique identification codes. Index births and subsequent births to the same mother were collated in order to examine relative birth order effects and to calculate birth intervals. RESULTS: Regression analysis showed significant associations between weight of the index birth and maternal age (p < 0.001), remoteness of locality (p < 0.01), sex of the infant (p < 0.001) and maternal height (p < 0.001). Length at birth was significantly associated with ethnicity of infant (Aboriginal vs Aboriginal/non-Aboriginal admixture, p < 0.05), sex (p < 0.001), remoteness (p < 0.01) and maternal height (p < 0.001). Similar associations were observed for second and subsequent births. Birth interval was not associated with birthweight or length. Low birthweight was also more common to Aboriginal mothers compared with mothers of Aboriginal/non-Aboriginal admixture (13.1% vs 9.2%; chi(2) = 5.1, p < 0.025) even though there were no differences in height between these two groups. Teenage mothers (< or =19 years) were no more likely to have low birthweight babies than older mothers. Of the variables examined, the only significant predictor of low birthweight was a previous low birthweight baby (relative risk = 4.45, p < 0.001). CONCLUSIONS: Short birth intervals and teenage births were not significant contributors to low birthweight in the present study. The high prevalence and duration of breastfeeding in the Kimberley may contribute to long average birth intervals. Pre-term birth, rather than intrauterine growth retardation, is likely to be the most common cause of low birthweight in this population.     

Trends in live births by mother's country of birth and other factors affecting low birthweight in England and Wales, 1983-2001

This article investigates trends in low birthweight singleton live births by mother's country of birth. 11.4 million birth records from registration data in England and Wales from 1983 to 2001 were used. The analysis focuses on births to mothers born in the UK and countries that contribute to the main ethnic minority groups in England and Wales. The results show that the prevalence of low birthweight babies varies by mother's country of birth. Important differentials also exist by mother's age at birth, multiplicity and registration status.     

Factors affecting birthweight of rural Australian Aborigines

Aim : To examine factors affecting birthweight of Aboriginal infants in the Kimberley region of north-west Australia. Research design : A retrospective study of maternal and infant health records obtained through routine data collection. Subjects and methods : Birthweight and length of 2959 infants born to 1822 women from 1986 to 1994 were analysed. Mothers and infants were matched using unique identification codes. Index births and subsequent births to the same mother were collated in order to examine relative birth order effects and to calculate birth intervals. Results : Regression analysis showed significant associations between weight of the index birth and maternal age ( p < 0.001), remoteness of locality ( p < 0.01), sex of the infant ( p < 0.001) and maternal height ( p < 0.001). Length at birth was significantly associated with ethnicity of infant (Aboriginal vs Aboriginal/non-Aboriginal admixture, p < 0.05), sex ( p < 0.001), remoteness ( p < 0.01) and maternal height ( p < 0.001). Similar associations were observed for second and subsequent births. Birth interval was not associated with birthweight or length. Low birthweight was also more common to Aboriginal mothers compared with mothers of Aboriginal/non-Aboriginal admixture (13.1% vs 9.2%; &#104 2 = 5.1, p < 0.025) even though there were no differences in height between these two groups. Teenage mothers ( &#114 19 years) were no more likely to have low birthweight babies than older mothers. Of the variables examined, the only significant predictor of low birthweight was a previous low birthweight baby (relative risk = 4.45, p < 0.001). Conclusions : Short birth intervals and teenage births were not significant contributors to low birthweight in the present study. The high prevalence and duration of breastfeeding in the Kimberley may contribute to long average birth intervals. Pre-term birth, rather than intrauterine growth retardation, is likely to be the most common cause of low birthweight in this population.     

Age at placement,adoption experience and adult adopted people's contact with their adoptive and birth mothers: An attachment perspective

Adoption holds particular interest for attachment researchers. Although children adopted as babies experience almost continuous care by their adoptive parents, older placed children experience at least one major change of caregiver when they join their adoptive family. Moreover, in the majority of cases, older placed children have generally suffered a pre-adoption history of abuse, neglect and/or rejection. It is now being recognized that older placed children's attachment histories and internal working models (IWMs) established in relationship with their initial carers remain active in relationship with their new carers. Transactional models have helped both researchers and practitioners to understand the dynamics of parent-child relationships in cases where insecure children with histories of neglect,abuse and rejection findthemselves in new caregiving environments. The present study examines the childhood experiences of adult adopted people and their current levels of contact with their adoptive mothers, and in cases where people had searched for and found a birth relative, current levels of contact with their birth mother. Although no information was collected on the adopted adult's pre-placement history,age at placementwas used as a proxy measure to examine whether older placed children reported different adoption experiences and what their current levels of contact were with their adoptive and birth mothers. The findings show that age at placement was associated with adopted people'sreported experiences of being adopted and current rates of contact with their adoptive and birth mothers, with those placed at older ages most likely to report that they (1) did not feel they belonged in their adoptive families while growing up, (2) did not feel loved by their adoptive mother, (3) were least likely to remain in highfrequency contact with their adoptive mother, and (4) were least likely to remain in high-frequency contact with their birth mother. An attachment perspective is used to interpret the findings. Children adopted at older ages appear more likely to have experienced an insecure attachment relationship with their adoptive mother.     

Gestational age, birthweight, and neonatal mortality for extremely premature inner-city African-American and Latino infants.

This article analyzes birthweight, gestational age, and inhospital survival for 233 extremely premature infants born at an inner-city hospital over the past 5 years. Results for gestation-specific birthweights and survival did not differ between inner-city Hispanic and African-American infants born at 24 to 28 weeks of gestation. For infants with gestation of 23 to 28 weeks, weight at birth increased by approximately 100 g/week gestation. Survival rates increased from 15% at 23 weeks to 75% by 28 weeks gestation. Survival in this sample was strongly affected by respiratory distress syndrome, air leak, and birthweight. Prenatal steroids administered to the mother had a significant effect on improving survival using univariate analysis and was at the limits of statistical significance using logistic regression. Other maternal, obstetric, and neonatal factors had little or no effects on survival in this group of very immature infants.     

Assessing the net effect of young maternal age on birthweight

Pregnancy during adolescence presents an increased risk for low birthweight, which is attributed not only to physiologic immaturity but also to socioeconomic and behavioral risk factors associated with adolescence. The independent effect of maternal age on birthweight is difficult to ascertain because age is closely entangled with these risks. We first examined the effect of being an adolescent mother on these risk pathways and then estimated the net effect of maternal age on birthweight (weight in grams or low birthweight (<2,500 g)) after controlling for these risks. We used data on 214 adolescent and 415 adult primiparae and their infants from the Cebu Longitudinal Health and Nutrition Survey, a community‐based survey in Metro Cebu, Philippines. Consistent with findings from other studies, adolescents in this sample were more socioeconomically disadvantaged, had poorer nutritional status during pregnancy, and received less prenatal care than adults. Bivariate analyses showed that infants of adolescents had a lower mean birthweight and were more at risk of low birthweight compared to those born to older mothers. When socioeconomic, biological, and behavioral risk factors were controlled for, young maternal age ceased to have an effect on birthweight in grams but remained a significant predictor of low birthweight. The common pathways through which maternal age influenced both birthweight variables were through its effects on maternal height and weight‐for‐height during pregnancy. In the model predicting birthweight in grams the maternal age effect was further manifested through prenatal care utilization. Am. J. Hum. Biol. 15:733–740, 2003. © 2003 Wiley‐Liss, Inc.     

Undernutrition prevalence and social determinants in children aged 0-59 months,Niterói,Brazil

Objective : With the aim of diagnosing the nutritional status and nutritional social-economic determinants in children aged 0-59 months, 2194 children were studied in the three Health Districts of the city of Niterói, Rio de Janeiro State, Brazil. Materials and methods : Data were obtained through a random sampling survey performed in the city's vaccination centres. Variables collected were maternal schooling, family income, dwelling's connection to safe water, dwelling's sewage connection, birthweight and the anthropometric indicators height / age ( H / A; for stunting), weight/height ( W / H ; for wasting) and weight / age ( W / A ; for underweight). Undernutrition risk factors were identified with the help of logistic regression models for the age ranges 0-12 and 13-36 months. Results : Stunting and underweight levels were found to be above those of the NCHS reference, although, in general, at levels better than those frequently found in Third World countries. Low birthweight prevalence in the city was 9%, also above common levels in more developed countries. Undernutrition risks were, in general, higher for the younger age range. The variables family income, maternal schooling, water connection and birthweight could be characterized as important undernutrition risk factors, being most noticeable the effects of family income and birthweight both for the '0-12 months' and for the 'above 13 months' age ranges. Conclusions : Although the city's problems are mostly concentrated on chronic undernutrition, more attention should be given to children's birthweight deficits, which appear to have effects on children's growth that extend for years after birth.     

Maternal postpartum behavior and the emergence of infant-mother and infant-father synchrony in preterm and full-term infants: the role of neonatal vagal tone

Relations between maternal postpartum behavior and the emergence of parent-infant relatedness as a function of infant autonomic maturity were examined in 56 premature infants (birthweight = 1000-1500 g) and 52 full-term infants. Maternal behavior, mother depressive symptoms, and infant cardiac vagal tone were assessed in the neonatal period. Infant-mother and infant-father synchrony, maternal and paternal affectionate touch, and the home environment were observed at 3 months. Premature birth was associated with higher maternal depression, less maternal behaviors, decreased infant alertness, and lower coordination of maternal behavior with infant alertness in the neonatal period. At 3 months, interactions between premature infants with their mothers and fathers were less synchronous. Interaction effects of premature birth and autonomic maturity indicated that preterm infants with low vagal tone received the lowest amounts of maternal behavior in the postpartum and the least maternal touch at 3 months. Infant-mother and infant-father synchrony were each predicted by cardiac vagal tone and maternal postpartum behavior in both the preterm and full-term groups. Among preterm infants, additional predictors of parent-infant synchrony were maternal depression (mother only) and the home environment (mother and father). Findings are consistent with evolutionary perspectives on the higher susceptibility of dysregulated infants to rearing contexts and underscore the compensatory mechanisms required for social-emotional growth under risk conditions for parent-infant bonding.     

Introducing new data on gestation-specific infant mortality among babies born in 2005 in England and Wales

Gestational age is highly correlated with birth outcomes including birthweight and infant mortality. Since gestational age is not recorded at the registration of live births in England and Wales, it has not been possible to produce routine statistics on gestation-specific infant mortality rates. A new system, introduced in 2002, for allocating NHS numbers at birth (NN4B) provided the opportunity to obtain gestational age information. NN4B records have been linked with birth registration data for all births occurring in 2005, and further linked with registration records for deaths in the first year of life. Thus, for the first time, we produce gestation-specific infant mortality rates for England and Wales as a whole, including in relation to birthweight, multiplicity, age of mother, marital status/registration type, and the National Statistics Socio-Economic Classification.     

The role of perinatal problems in risk of co-morbid psychiatric and medical disorders in adulthood

BACKGROUND: Perinatal problems may be associated with an increased risk for psychological and physical health problems in adulthood, although it is unclear which perinatal problems (low birthweight, preterm birth, low Apgar scores, and small head circumference), or what clusters of problems, are more likely to be associated with later health problems. It is also not known whether perinatal problems (singly or together) are associated with co-morbidity between psychological and physical health problems. METHOD: A regional random sample (from Baltimore) of mothers and their children (n=1525) was followed from birth to adulthood (mean age 29 years). Perinatal conditions were measured at delivery. Psychological problems (depression and suicidal ideation) were measured with the General Health Questionnaire-28 (GHQ-28) and physical problems (asthma and hypertension) with the RAND-36 Health Status Inventory. RESULTS: Children with perinatal problems were generally at increased risk for depression, suicidal ideation and hypertension, and co-morbid depression and hypertension even after controlling for confounders. One possible underlying condition, preterm low birthweight (LBW), extracted by cluster analysis, considering all of the four perinatal problems, was associated with increased risk for psychological and physical health outcomes as well as co-morbidity of the two. CONCLUSIONS: LBW, preterm birth and small head circumference singly increased the risk for both psychological and physical health problems, as well as co-morbid depression and hypertension, while low Apgar scores were only associated with psychological problems. Delineating different etiological processes, such as preterm LBW, considering various perinatal problems simultaneously, might be of benefit to understanding the fetal origin of adult illness and co-morbidity.     

Influence of chest/head circumference ratio at birth on obstetric and neonatal outcomes: The Japan environment and children's study

Objectives

Some newborns that are not small-for-gestational-age (non-SGA, birthweight ≥10th percentile for a given gestational age) may have pathologic growth restrictions. This study examined the association of adverse obstetric and neonatal outcomes with chest/head circumference ratio at birth in non-SGA and SGA newborns.

Methods

This study was a cross-sectional evaluation of data from a nationwide prospective birth cohort study, the Japan Environment and Children's Study. We analyzed 93 690 non-anomalous singletons born at 34–41 gestational weeks. We defined low, normal, and high chest/head circumference ratio as <10th percentile, 10th–90th percentile, and >90th percentile, respectively, according to the internally constructed chest/head circumference percentile chart. Modified Poisson regression was used to estimate adjusted prevalence ratios (aPR) for the outcomes studied.

Results

Compared with non-SGA newborns with a normal ratio, those with a low ratio had an increased occurrence of low birthweight (1.75, 1.58–1.94 [aPR, 95% confidence interval]), cesarean delivery (1.34, 1.29–1.38), Apgar score <7 at 5 min (1.57, 1.14–2.17), respiratory complications (1.20, 1.04–1.39), and prolonged hospitalization (1.36, 1.30–1.42). In contrast, the high-ratio group had a lower rate of low birthweight (0.71, 0.59–0.86), cesarean delivery (0.82, 0.77–0.87), and prolonged hospitalization (0.83, 0.78–0.89). In SGA newborns, a low ratio was associated with increased aPRs for low birthweight, cesarean delivery, hypoglycemia, and prolonged hospitalization, whereas a high ratio showed no such association.

Conclusions

Findings indicate that the chest/head circumference ratio at birth influence obstetric and neonatal outcomes regardless of the birthweight status.     

Low birthweight in African Americans: does intergenerational well-being improve outcome?

The primary antecedent of infant mortality is low birthweight. Vital statistics data have shown that women of low socioeconomic status, regardless of race, are at greater risk for delivering low birthweight infants; however, prevailing data show that black women of the same socioeconomic status as white women have a twofold higher risk of giving birth to an infant weighing < 2500 g and a threefold risk of delivering a very low birthweight infant weighing < 1500 g. There is also evidence that intergenerational effects on birth outcome exist. However, virtually all studies of the effect of socioeconomic status on perinatal outcome have been cross-sectional; the effect of sustained intergenerational well-being has not been measured. To address this gap, this study was designed to demonstrate that in an African-American population with sustained high socioeconomic status and equal risk factors, the birthweight distribution and other reproductive outcomes are the same as those for comparable US white populations. Preliminary findings are reported here.     

Serum insulin-like growth factor-I concentrations in late middle age: no association with birthweight in three UK cohorts

BACKGROUND: Small body size at birth and during infancy is associated with an increased risk of adult osteoporosis and cardiovascular disease. Fetal programming of the growth hormone-insulin-like growth factor (GH-IGF) axis may provide a mechanism for these epidemiological findings. AIMS: To determine whether measurements of GH and IGF-I in late middle age were related to size at birth and in infancy. METHODS: Overnight urinary GH excretion and fasting serum IGF-I were measured in 309 men and 193 women from Hertfordshire (born 1920-1930) for whom birthweight and weight at 1 year were recorded. Serum IGF-I was measured in men and women from Preston (n=254, born 1935-1943) and Sheffield (n=215, born 1939-1940) whose birthweight and other birth measurements were recorded. RESULTS: Urinary GH and serum IGF-I were not related to birthweight, other measurements at birth, or weight at 1 year. CONCLUSION: In contrast to previous studies in children or young adults, these data do not support the hypothesis that IGF-I concentrations are programmed by intra-uterine events, as assessed by birthweight, in late middle age.     

The seasonality of live birth is strongly influenced by socio-demographic factors.

The number of births varies markedly by season, but the causes of this variation are not well understood. The proposed explanations include temperature or photoperiod (affecting hormonal concentrations, sperm quality or sexual activity), seasonal variation in pregnancy loss, or cultural factors. In this paper we examined whether birth seasonality is influenced by socio-demographic factors. We used data on all live births registered in the Czech Republic in 1989-1991 (n = 387 496). Differences in the degree of seasonality between socio-demographic groups (defined by maternal age, marital status, education and birth order) were examined by inspection of curves, by comparing coefficients of variations of monthly numbers of births, and by calculating the ratios of the number of births in the 3 peak months (March to May) to the number of births in the 3 lowest months (October to December). We found large differences in the size of the seasonal variation in births by socio-demographic factors. The seasonal variation was highly pronounced in mothers who were 25-34 years old, had higher education, were married, and were pregnant with their second or third child. By contrast, birth seasonality was weak in mothers who were < or =19 years or > or =35 years old, unmarried, had low education, and expected their first or fourth or higher order birth. In a multivariate model, all four socio-demographic variables contributed significantly to seasonal variation. These results suggest that the seasonality of births is, at least in this population, strongly influenced by socio-demographic factors.     

Infant birthweight in the US: the role of preconception stressful life events and substance use

The purpose of this study was to determine the relationships among preconception stressful life events (PSLEs), women’s alcohol and tobacco use before and during pregnancy, and infant birthweight. Data were from the Early Childhood Longitudinal Study-Birth Cohort (n?=?9,350). Data were collected in 2001. Exposure to PSLEs was defined by indications of death of a parent, spouse, or previous live born child; divorce or marital separation; or fertility problems prior to conception. Survey data determined alcohol and tobacco usage during the 3 months prior to and in the final 3 months of pregnancy. We used staged multivariable logistic regression to estimate the effects of women’s substance use and PSLEs on the risk of having a very low (<1,500 g, VLBW) or low (1,500–2,499 g, LBW) birthweight infant, adjusting for confounders. Women who experienced any PSLE were more likely to give birth to VLBW infants (adjusted odds ratio [AOR]?=?1.35; 95 % confidence interval [CI]?=?1.10–1.66) than women who did not experience any PSLE. Compared to women who never smoked, women who smoked prior to conception (AOR?=?1.31; 95 % CI?=?1.04–1.66) or during their last trimester (AOR?=?1.98; 95 % CI?=?1.56–2.52) were more likely to give birth to LBW infants. PSLEs and women’s tobacco use before and during pregnancy are independent risk factors for having a lower birthweight baby. Interventions to improve birth outcomes may need to address women’s health and health behaviors in the preconception period.     

Maternal pelvic size,measured by dual energy X-ray absorptiometry,predicts infant birthweight

Indicators of infant birthweight are important because infant birthweight is related to later health outcomes. This study developed and validated new measures of the pelvis from dual energy absorptiometry (DEXA). Predictors of the new measures of maternal pelvic size were examined and the pelvic size measures were examined as predictors of infant birthweight. Data were drawn from a sample of 326 women in Hawaii and their 608 infants. The women were 45–60 years old at the time of the DEXA bone scan and when they recalled the birthweights of their infants. The birthweights were validated with birth certificate data. The women were participants in the Early Postmenopausal Interventional Cohort (EPIC) to study the effects of alendronate on bone density. Questions on birth histories were added to that study. Adolescent milk consumption and age at menarche were positively associated with the DEXA hip measure, while Asian ethnicity was negatively associated with the hip measure in multiple regression analysis. In multiple regression analysis, the hip measure, together with infant gender and gestational age predicted infant birthweight; mother's height, weight, and ethnicity did not add significantly to the model. DEXA provided measures of the pelvis, which varied by ethnicity, hormonal and nutritional variables, and which were indicators of infant birthweight. Am. J. Hum. Biol. 12:552–557, 2000. © 2000 Wiley-Liss, Inc.     

Intergenerational effects of high socioeconomic status on low birthweight and preterm birth in African Americans

As socioeconomic status (SES) increases, the incidence of low birthweight and preterm birth decreases irrespective of social class. However, low birthweight remains twice as high for African-American women as for white women even when SES is controlled. This study examines to what extent second generation high SES African-American women experience improvement in birthweight and gestational age. One hundred eighty-nine former Meharry students were surveyed. Identified were 934 births that are the children and grandchildren of these students who matriculated at Meharry. These infants are compared with a cohort of white mothers from a study in the School of Public Health at Yale University. Low birthweight was reduced in the third generation high SES African-American children (6.9%) from the second generation (11.4%) but remained higher than white children (3.3%). Results showed that African-American third generation children remained at higher risk for low birthweight than were white children (relative risk [RR], 1.78; 95% confidence interval [CI], 1.03, 3.09). Similar results were observed for preterm delivery where the increased risk to third generation African-American children was 3.16 (1.89, 5.27). Persistent strong ethnic differences in birthweight in this high SES cohort (OR = 3.16, 95% CI, 1.89-5.27) support a conclusion that African-American women have birthweight distributions that are somewhat lighter than white women. This may explain a portion of current ethnic differences in birthweight. It is also possible that persistent psychosocial and behavioral factors continue to negatively influence birthweight, even in second generation high SES African-American mothers. This explanation will require identification of powerful risk factors, which are largely unrelated to those presently under investigation.     

Secular trend in birthweight among the Purari delta population, Papua New Guinea

The aim of this analysis was to examine the extent and possible seasonal nature of the secular trend in mean birthweight in the Purari delta, Papua New Guinea. This is a country undergoing rapid modernization, and with this has come a secular trend toward increased adult body size in some parts of the country but not others. Birthweight data, collected by month of delivery at Kapuna Hospital in the Purari delta between the years 1969 and 1996, was analysed by year of birth and by season, using one-way analysis of variance and post hoc Scheffé tests with the statistical software SPSS-PC+. A total of 927 birthweights for the years 1969, 1972, 1977, 1994 and 1996 were included in the analysis. Twin births were excluded from analysis, as were births below 1.5 kg. There is clear evidence of a secular trend in increasing mean birthweight between the period 1969 and 1996, with the largest significant difference being between 1977 and 1994, from 2.70 to 2.92 kg. There were no significant differences in mean birthweight between the sexes. The rate of birthweight increase between 1977 and 1994 was 130 g per decade, lower than the gain of 200 g per decade in the period 1994-1996. The decline in birthweight of 90 g per decade during the period 1969-1977 is not statistically significant. The proportion of infants born with low birth weight (< 2.5 kg) shows an increase between 1969 and 1972, and a decline thereafter. While seasonal differences in birthweight during any of the years examined is non-significant, significantly greater mean birthweight across the period 1969-1996 was found for births during the wet season (April to July), and the drier season (August to November), respectively. The secular increase in mean birthweight is likely to be a consequence of the improvements in maternal diet and increased maternal body size that have come with economic modernization. The secular trend of seasonality in mean birthweight among the Purari delta population may be a function of seasonally varied displacement of traditional diet by non-local bought foods, as well as reduced seasonality of maternal workload associated with the processing of the traditional staple food.