Twin births in Yucatan, Mexico during 2008-2020: trends in maternal sociodemographic factors and differences in birth weight and length according to sex of co-twin.

Background: Over the years, there has been a noticeable increase in the incidence of multiple pregnancies, due in part to the increased use of assisted reproductive technologies in recent years. The increase in twin pregnancies constitutes a public health challenge due to the adverse outcomes sometimes they entail. Twin pregnancies inherently carry a higher risk of complications, and one of the critical associated factors is the risk of low birth weight. Twin birth weight discordance among different populations can be attributed to differences in non-shared environmental influences. The presence of two or more fetuses in the uterus may lead to an unequal distribution of nutritional and oxygen resources, increasing the likelihood that at least one of the twins will experience insufficient fetal development. Other factors, such as ethnicity, genetics, sociodemographic characteristics, gestational age, parity, and chorion type, have also been related to the birth weight discordance in twin pregnancies. However, it is unclear to what extent the associations between these factors can explain the differences in birth and length size. The frequency of twin births varies among populations and over time, so it is crucial to gain a deeper understanding of the factors contributing to the rise in the twinning rate. The official records of twins continue to make significant contributions to our understanding of the causes of individual differences, and new twin registries are still being created. The recent availability of data from developing countries allows the analysis of trends in regions with sociodemographic and reproductive profiles. Obtaining a more comprehensive understanding of the epidemiology, as well as the related morbidity and mortality, is clinically crucial. Objectives: The aim of the study was to describe the trends of twin births in Yucatan, Mexico during 2008-2021, analyze their association with maternal sociodemographic factors, and compare birth outcomes between types of twin pairs: female-female, male-male, and female-male. Methods: A retrospective cohort analysis was conducted using data from the Mexican Ministry of Health, encompassing information on all births registered in the State of Yucatán, Mexico, from 2008 through 2021. The data was obtained from both public and private hospitals. The variables, including date of birth, sex, gestational age, birth weight and length of newborns, mother´s date of birth, educational level, and number of previous live offspring, were extracted from each dataset. Multiple births (three or more) were excluded from the study. We graphically analyzed the rates (per 1000 births) and percentages of twins according to maternal age, education level, and parity during the study period. A multiple logistic regression model was used to analyze the association between maternal sociodemographic factors and the occurrence of twin births. Comparisons of the gestational age and birth weight and length between types of twin pairs were performed using analysis of variance. Results: A total of 478,118 live births, including 1.4% twins (accounting 6,766 twin births), were analyzed. The rates increased from 11.21 during 2008-2011 to 13.34 during 2012-2017 and reached 20.08 in 2019. The percentages increased in women aged ≥30 years and those with higher educational levels. Older maternal age (coefficient = 0.03; OR = 1.03, per each year), greater education level (coefficient = 0.55 and OR= 1.74 for medium and coefficient = 1.05; OR = 2.57 for high level, compared with no education) and higher parity (coefficient= 0.26; OR = 1.30 per each previous offspring) increased the odds for having twins. Twins' male-male showed a slightly increased of preterm birth than a co-twin female. Opposite-sex twins showed measurable but small increases in birth weight and length compared with same-sex twins. Conclusion: The rate of twins in Yucatan increased substantially during 2008-2020 in specific sociodemographic groups. Opposite-sex twins were slightly larger than same-sex twins at birth.

Birthweight and its association with cardiometabolic risk parameters in rural Maya children from Yucatan, Mexico.

BACKGROUND: Knowledge about the influence of early developmental factors on cardiometabolic health in the Maya is limited. AIM: To analyse the relationship between birthweight (BW) and cardiometabolic parameters in a sample of rural Maya children from Yucatan, Mexico. SUBJECTS AND METHODS: We took anthropometric measurements and obtained data on BW and fasting blood samples in a sample of 75 children aged 5-14 years. Dependent variables were: fat mass index (FMI), body mass index (BMI), glucose (G), triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), LDL/HDL and TC/HDL ratios and metabolic index (TGxG/HDL2). Outcomes were transformed to y = 100 log(e)x and the resulting estimates are interpreted as symmetrical percentage differences. The main independent variable was BW z-score. Multiple linear regression analyses were used to assess the relationship between BW and outcomes. RESULTS: An increase of one standard deviation in BW predicted 6.6% (95% CI [-11.6, -1.6]) decrease in HDL and 11% (95% CI [3.7, 18.4]), 7.8% (95% CI [2.3, 13.2]) and 19.6% (95% CI [3.1, 36]) increases in LDL/HDL, TC/HDL and metabolic index, respectively. CONCLUSION: Higher birthweights were associated with adverse levels of biochemical parameters in this sample of rural Maya children.

Secular trends in the anthropometric characteristics of children in a rural community in Yucatan, Mexico.

OBJECTIVE: To analyze changes in height, weight, and body mass index (BMI = kg/m2 ) from 1986 to 2022 in 3-11 year old children from Dzeal, a rural Maya community in Yucatan, Mexico. MATERIALS AND METHODS: From October-2022 to February-2023 (third-wave survey), we obtained anthropometric measurements of children (n = 80) and family socioeconomic data and compared them with data obtained in 1986 (n = 38) and 2000 (n = 76). Comparisons of anthropometric parameters by sex between years of measurement were performed graphically and through one-way ANOVA, splitting children into two age groups: 3-7 and 8-11. Bonferroni adjustments for multiple comparisons were used when ANOVAs were statistically significant (p < .05). RESULTS: In girls, significant increases in height and weight between surveys were found in 3-7 and 8-11 age groups; in boys, significant increases were only found in the 8-11 age group. Regarding BMI, there were increases in 2022 compared with 1986/2000 in both sexes from 8 years onwards. Differences indicate increases of 3.9 and 4.4 cm per decade in girls aged 3-7 and 8-11, respectively, and increases in weight of 1.1 and 3.3 kg per decade, respectively. Increases in boys 8-11 years were 2.3 cm and 2.4 kg per decade. CONCLUSION: Significant increases in growth parameters were observed in specific-age children in the community studied in the context of changes in livelihoods and improvements in household material conditions.

The impact of COVID-19 on the number of births in Yucatan, Mexico.

OBJECTIVE: To analyze the impact of COVID-19 on the number of births in Yucatan, Mexico during 2020 and 2021. MATERIAL AND METHODS: A total of 470 651 live births occurred in Yucatan from January 1st, 2008, to December 31st, 2021, and were included in the analysis. The monthly number of births observed during January 2008-February 2020 was used to describe pre-pandemic trends. Time-series analysis was applied to examine whether the number of births observed from December 2020 (9 months after the beginning of the pandemic) to December 2021 differed from the expected values. Trends in the number of births according to maternal age, parity and education were examined to identify changes differentiated by sociodemographic characteristics. RESULTS: The number of births in 2021 decreased by 18% (5869 births) compared with 2019, which represents a reduction from 12.89 to 12.48 per thousand inhabitants. The observed number of births from December 2020 to July 2021 was significantly lower than the figure expected. April (expected = 2863 vs. observed = 1722), May (expected = 2948 vs. observed = 1990), and June (expected = 2997 vs. observed = 1978) 2021 showed the largest differences between expected and observed values. Then, from August to December 2021, the observed number of births fell within the expected range. Birth decline was slightly more pronounced among mothers between 20 and 29 years of age and in those without previous offspring. CONCLUSION: We provide evidence of birth decline in Yucatan during the COVID-19 pandemic. Birth rate reduction in Yucatan doubled the world average and young women without children were the most affected.

Five-year survival after retroperitoneal oncologic resection with and without vascular surgeon intervention.

OBJECTIVES: Retroperitoneal tumor resection commonly disturbs major vessels; therefore, surgical teams can recruit vascular surgeons to prevent injuries and improve the prognosis of oncologic patients. The objective of the present study is to establish long-term survival after retroperitoneal tumor resection surgery with an emphasis on the potential impact of preventing or repairing major vessel injuries when tumors are adjacent to the aorta or vena cava. METHODS: Retrospective case series including all cases of surgical removal of retroperitoneal tumors between 2007 and 2020 in a highly specialized hospital in Mexico City. Long-term survival was defined as 5 years after surgical intervention. Descriptive statistics, group-comparison tests, and regression analysis were performed using Stata 16. RESULTS: From a total of 70 cases, vascular injury occurred in 30 (42.8%) and the vascular surgeon intervened in 19 (27.1%) of them, 4 (21%) were performed by a vascular surgeon with planned intervention, and in 9 (47.3%) cases the vascular surgeon was called to join the surgery due to emergency. Intraoperative bleeding was 2-fold greater in the group with an emergent participation of vascular surgery in contrast with the planned intervention group (4, 235 mL vs 2, 035 mL, p = 0.04). The regression model revealed a significant association between the intervention of a vascular surgeon and long-term survival (OR 59.3, p = 0.03) after adjusting for sociodemographic and characteristics of oncologic nature. CONCLUSIONS: Planned intervention of vascular surgeons in retroperitoneal tumor resection may have a positive impact not only in trans-operatory period, but also on long-term survival.

Análisis de la diversidad dietética en mujeres embarazadas del sureste de México

Objetivo: Describir la diversidad dietética (DD) de un grupo de mujeres embarazadas del municipio de Mérida, Yucatán. Métodos: Se aplicó un cuestionario socioeconómico y tres recordatorios de 24 horas (R-24) en días no consecutivos a 83 mujeres embarazadas. La DD se evaluó a nivel individual de acuerdo a la puntuación Mínima de Diversidad Dietética para la Mujer (MDD-W). Se consideró una DD alta cuando se consumieron ≥5 grupos de alimentos y DD baja cuando el consumo fue <5. Se analizaron las diferencias en el consumo de los grupos de alimentos de acuerdo al nivel de DD mediante pruebas de Chi2. Resultados: La edad promedio de la muestra fue de 27,6 años (±5,2), con una edad gestacional promedio de 23 semanas (±8,3). La media de la DD fue de 4,9 (±1,5) grupos de alimentos. El 39% de la muestra tuvo una DD baja. Las mujeres con DD baja consumieron en menor frecuencia alimentos cárnicos, huevos, vegetales de hoja verde oscuro, frutas y verduras ricas en vitamina A, otras verduras y otras frutas (P= <0,05). La proporción de mujeres con DD baja fue mayor durante los fines de semana (49% vs 68%, Chi2= 7,89, P= 0,005). Conclusiones: La media de la DD obtenida en esta muestra indica una DD baja. Las mujeres en este estudio presentaron un bajo consumo de alimentos ricos en vitaminas mientras que los alimentos ricos en energía y proteína de origen animal presentan un consumo alto.

Objective: To describe the dietary diversity (DD) in a sample of pregnant women from Merida, Yucatan. Methods: We applied a socioeconomic questionnaire and three 24-h dietary recalls, on non-consecutive days, to 83 pregnant women residing in Merida, Yucatan. DD was assessed according to the Minimum Dietary Diversity score for Women (MDD-W). A high DD was considered when a consumption ≥5 food groups occurred, while a consumption <5 groups was considered as a low DD. We analyze the differences in the consumption of food groups according to the level of DD. Chi square test were applied to assess DD. Results: The mean age of participants was 27.6 years (±5.2) and the average gestational age was 23 weeks (±8.3). The mean DD was 4.9 (±1.5) food groups and 39% of the sample had a low DD. Women with low DD consumed less frequently meat foods, eggs, dark green leafy vegetables, fruits and vegetables rich in vitamin A, other vegetables and other fruits (P<=0.05). Low DD was more frequently registered during weekend days (49% vs 68%, P= 0.005). Conclusions: The sample had low DD. Women who participated in this study had a low consumption of foods rich in micronutrients while foods rich in energy and protein of animal origin had a high consumption.

The relationship between pre-pregnancy BMI and energy and macronutrients intakes during pregnancy in women from Yucatan, Mexico.

In this observational study, our aim was to analyse the association between pre-pregnancy BMI and adequacy rates of energy and macronutrient intakes in a sample of pregnant women from Yucatan, Mexico. From September to December 2019, we collected data on socioeconomic, pregnancy, and dietary characteristics, and took anthropometric measurements of women during household visits. Pre-pregnancy BMI was calculated from measured height and self-reported body weight. Energy and macronutrient intakes (obtained from three 24-h dietary recalls) were compared with the estimated trimester-specific requirements to calculate adequacies (%). Multiple linear regression models showed that after accounting for maternal socioeconomic characteristics and perinatal variables, each unit increase in pre-pregnancy BMI was associated with decreases of 2%, 2%, and 2.6% in energy, carbohydrate, and total fat intakes, respectively. These results were significant when under- and over-reporters were excluded from the analyses. Women who enter pregnancy with higher BMI values may voluntarily or involuntarily reduce their food intake.IMPACT STATEMENTWhat is already know about this subject? Some studies have analysed the relationship between pre-pregnancy BMI categories (normal weight, overweight, and obesity) and diet quality during pregnancy, but few studies have focussed on quantitative energy and macronutrient intakes or their adequacies in relation to pre-pregnancy BMI.What do the results of this study contribute? In this sample of Mexican women belonging to a middle socioeconomic status, we found that after excluding under- and over-reporters from the analyses and accounting for maternal socioeconomic characteristics and perinatal variables, BMI was negatively associated with adequacy intake rates of energy, carbohydrates, and total fats during pregnancy.What are the implications of these findings for clinical practice and/or further research? Women who enter pregnancy with higher BMI values may voluntarily or involuntarily reduce their food intake. These results can be used to accordingly plan diet counselling during pregnancy.

Differential fetal growth rates mediated by sociodemographic factors in Yucatan, Mexico: an epidemiological study.

BACKGROUND: Fetal growth restriction (FGR) may be related to ethnicity. Additionally, ethnic groups experience adverse socioeconomic circumstances that increase FGR risk. However, the dearth of evidence of the interaction between socioeconomic factors and FGR highlights the need for additional research. OBJECTIVE: To analyze the association between socioeconomic factors and FGR in Maya and non-Maya populations in Yucatan, Mexico. METHODS: A total of 21,320 singleton births in 2017 in Yucatan were analyzed. The student's t-test and the chi-square test were used to compare the means and proportions of maternal and perinatal variables between the FGR group and the birthweight appropriate for gestational age (AGA) group. Path analysis was performed to identify the direct and indirect effects of socioeconomic factors on FGR and mediators between predictors and FGR. RESULTS: The prevalence of FGR at birth was 9.06%; this rate was higher in the Maya population (12.4, 95% CI 11.3-13.5), without differences between socioeconomic levels. Path analysis revealed sociostructural variables (ethnicity and poverty) are reliable predictors of FGR at birth mediated by maternal education (ß = -.152, p < .001) and teenage pregnancy (ß = .065, p = .037). The proposal path model had a good fit index CFI = .968, TLI = .920, RMSEA = .046. CONCLUSION: The prevalence of FGR was higher among Maya women than non-Maya women The socioeconomic conditions associated with FGR at birth were ethnicity, poverty, maternal education, and teenage pregnancy. Maternal education and teenage pregnancy act as mediators between sociostructural variables and FGR at birth.

Development of birthweight and length for gestational age and sex references in Yucatan, Mexico.

OBJECTIVE: To develop sex- and gestational age specific reference percentiles and curves for birth weight and length for Yucatec neonates using data from birth registers of infants born during 2015-2019. MATERIAL AND METHODS: Observational, descriptive, epidemiologic study in a 5-year period including every registered birth in the state of Yucatan, Mexico using birth registries. A total of 158 432 live, physically healthy singletons (76 442 females and 81 990 males) between 25 and 42 weeks of gestation were included in the analysis. We used the LMS method to construct smoothed reference centiles (3rd, 10th, 25th, 50th, 75th, 95th, and 97th) and curves for males and females separately. RESULTS: Mean maternal age was 26 (SD = 6.22) years. Fifty-two percent of births occurred by vaginal delivery, 37% were firstborn and similar proportions were second (33%) and third or more (30%) born. 5.5% of newborns included in the references corresponds to neonates born before 37 weeks of gestation (5.9% boys and 5.1% girls). In both sexes, the percentage of infants with a birthweight less than 2500 g was 6.7%. The birthweight at the 50th percentile for males and females at 40 weeks of gestation in this cohort was 3256 and 3167 g, respectively, and the corresponding values for birth length were 50.23 and 49.84 cm (mean differences between sexes: 89 g and 0.40 cm, respectively). CONCLUSION: The reference percentile and curves developed in this study are useful for research purposes and can help health practitioners to assess the biological status of infants born in Yucatán.

The Associations Between Maternal Socioeconomic Factors and Adequacy of Energy and Macronutrient Intakes in Pregnant Women From Yucatan, Mexico.

BACKGROUND: Socioeconomic factors influence diet quality during pregnancy. However, a dearth of evidence about the influence on energy and macronutrients adequacy calls for research. OBJECTIVE: To analyze the association between socioeconomic factors and adequacy rates of energy and macronutrient intakes in pregnant women from Merida, Yucatan, Mexico. METHODS: During September to December 2019, we applied a socioeconomic questionnaire and three 24-hour dietary recalls to 83 pregnant females resident in Merida, Yucatan. Energy and macronutrient intakes were compared with the estimated trimester-specific energy and macronutrient requirements to calculate adequacies (%). Outcome variables were average adequacy of energy, carbohydrates, total fat, and protein intakes and the main predictors were maternal education, monthly family income, working status, and marital status. Descriptive statistics of adequacy were calculated for each category of predictors. The association between socioeconomic factors and outcome variables was analyzed through simple and multiple linear regression models. RESULTS: Adequacy rates of energy and macronutrients decreased as education and familial income levels increased, as well as among unemployed women. Consistently with these results, simple linear regressions showed that years of education, family income, and working status (i.e., women working to earn money), were negatively associated with adequacy rates of energy and macronutrients intakes. When all predictors and covariates were included in a multiple linear regression model, only having a job was significantly associated with adequacy rates. Marital status was not associated with outcomes. CONCLUSIONS: Women in disadvantaged socioeconomic conditions (unemployed and low levels of education and familial income) show greater energy and macronutrient intakes.

Ethnic and sociodemographic correlates of developmental dysplasia of the hip in newborns from Yucatan, Mexico.

OBJECTIVES: To provide an insight of the incidence of congenital developmental dysplasia of the hip in newborns from Yucatan born between 2015 and 2019 and analyze its association with maternal sociodemographic characteristics and neonatal, pregnancy and delivery related aspects. METHODS: Retrospective, population-based study from Birth Registries database in Yucatan, Mexico between 2015 and 2019. Presence of hip dysplasia was described and analyzed considering three aspects (I) Maternal information (II) Pregnancy and birth (III) Neonatal examination. We obtained incidence rates from each year and the complete studied period. Association between hip dysplasia and maternal, neonatal and pregnancy/delivery variables was analyzed using logistic regression, unadjusted odds ratio and an adjusted model. RESULTS: Hip dysplasia occurred in 13 per 10 000 live births. Significant associations were found between hip dysplasia and maternal place of residence in a city <50 000 inhabitants, without a local clinic. Propensity to give birth to a neonate with hip dysplasia increased with maternal age and ethnicity, in female newborns and when total number of pregnancy consultations summed <5. Newborns with hip dysplasia were heavier and less susceptible to be delivered vaginally. Congenital developmental hip dysplasia was comparatively more frequent among offspring of Mayan women and suboptimal access to medical care during pregnancy. Female neonates were affected the most, those first-borns. Neonates with hip dysplasia were heavier and more susceptible to be born by cesarean section. CONCLUSION: Maternal, neonatal, and perinatal factors are associated with DDH in Yucatecan infants born during 2015-2019. Factors that describe living conditions seems to have a more important effect on the presence of this condition.

Maternal Grandmothers' Household Residency, Children's Growth, and Body Composition Are Not Related in Urban Maya Families from Yucatan.

This study analyzes the influence of grandmothers' household residency on the presence of low height-for-age and excessive fat (FMI = fat mass [kg]/height [m2]), waist circumference, and sum of triceps and subscapular skinfolds in a sample of 247 6- to 8-year-old urban Maya children from Yucatan, Mexico. Between September 2011 and January 2014, we obtained anthropometric and body composition data from children and mothers, as well as socioeconomic characteristics of participants and households. Grandmothers' place of residence was categorized as either in the same household as their grandchildren (n = 71) or in separate households (n = 176). Multiple logistic regression models were used to analyze the association between grandmothers' residency and outcome variables. Models were adjusted for maternal anthropometric characteristics and the following socioeconomic variables: family size, location, maternal education, monthly family income, and household crowding. Models showed that the presence of grandmothers in their grandchildren's households was not associated with any of the outcome variables. In contrast, larger family size, overcrowding in the household, and lower family income predicted low height-for-age in children. Larger family size decreased the risk for being overweight based on the three parameters of body composition. Overcrowding in the household increased the risk for greater skinfolds thickness, while low family income increased the risk for higher fat mass index. The residency of grandmothers in their adult daughters' households is not significantly associated with the outcome variables in this sample of urban Maya families. Instead, maternal anthropometric characteristics and socioeconomic conditions of the family have a greater influence on the overall growth of children.

The association between maternal and foetal factors with birth weight discordance in twins from Yucatan, Mexico.

Birth weight discordance (BWD) is not an uncommon event in twin pregnancies and can be associated with maternal and newborn characteristics. We aimed to analyse the association between maternal sociodemographic and newborn characteristics with BWD in twin infants born in Yucatan, Mexico, during 2008-2017 (n = 2091 pairs). BWD was calculated as the percentage of birth weight of the heavier twin. We defined three categories of BWD: concordant twins: <15%, mild-discordant: 15-24%, and severe discordant: ≥25%. A multinomial logistic regression model was used to analyse the association between maternal sociodemographic and newborn characteristics with BWD. Seventy-four percent (n = 1547) of twin pairs were classified as concordant, 17% (n = 356) met the criteria for mild-discordance and 9% (n = 188) for severe discordance. The odds for mild-discordance were significantly lower for mothers with medium level of education and in the highest quartile of total twin birth weight (TBW). Opposite-sex twin pairs showed increased odds for mild-discordance compared with same-sex pairs. The odds for severe discordance increased as mothers were in older age groups and decreased as TBW increased. Our rates of BWD are similar to those reported in populations from wealthier countries and maternal age and education, infants' sex, and TBW are associated with BWD.

Cephalopelvic disproportion as primary diagnosis for cesarean section: Role of neonatal birthweight in relation to maternal height at a Hospital in Merida, Mexico.

OBJECTIVE: To analyze the association between newborn and maternal characteristics and the risk for cesarean section (CS) due to cephalopelvic disproportion (CPD) and non-CPD causes compared to vaginal deliveries (VD) in a sample of infants and mothers from Merida, Yucatan, Mexico. METHODS: The final sample consisted of 3453 single, live, and term infants born between January 2016 and May 2017 at the Maternal-Infant Hospital in Merida and their mothers (aged ≥19 years). The mode of delivery was established as the dependent variables: (a) VD, (b) CS due to CPD, and (c) non-CPD CS. Independent variables were maternal height and weight, the number of previous VD, newborn weight, and neonatal birthweight (BW) index/maternal height index. A multinomial regression model was used to analyze the association between newborn and maternal characteristics and outcome variable. RESULTS: By mode of delivery, 2124 (62%) births corresponded to VD, 1042 (30%) to non-CPDCS, and 287 (8%) to CS due to CPD. Mothers who had CS due to CPD weighed more at the end of their pregnancy and were shorter. Maternal age and weight increased the risk for having CS due to CPD compared to VD and maternal height, and the number of previous VD reduces the risk for experiencing CS due to CPD compared to vaginal births. The relative risk ratio for higher neonatal BW/maternal height index was significant for CS due to CPD and non-CPD CS. CONCLUSION: According to our results from a public hospital in Merida, Mexico, CPD is a result of the interrelation of maternal and fetal size, rather than an independent result of maternal height or BW.

Birth weight and body composition in 6-to-8 years old Maya children.

OBJECTIVE: To test the hypothesis that fetal growth, indexed by birth weight (BW), induce metabolic adjustments in the fetus that will be reflected in differences in body composition in a sample of 6-to 8-years old urban Maya children from Yucatan, Mexico. METHODS: We measured height (cm), weight (kg) and triceps skinfold (mm) in 260 children (boys: 132, girls: 128), and height (cm) and weight (kg) in their mothers. Body composition was estimated in children through bioelectrical impedance analysis. Outcome variables were fat free-mass index (FFMI = fat-free mass [kg]/height [m]2 ) and fat mass index (FMI = fat mass [kg]/height [m]2 ). The main independent variable was BW z-scores. Multiple linear regression models were used to analyze the association between BW z-scores and outcome variables measured during childhood. Separate analyses were done for boys and girls. Complementary models were run using outcomes as z-scores. Models were adjusted for location, children's and mothers' age, mother's body mass index and household overcrowding index. RESULTS: BW in boys was positively associated with FFMI and FMI. FFMI increase 0.34 kg/m2 per 1-SD increase in BW and FMI increase 0.40 kg/m2 per 1-SD increase in BW. When outcomes were used as z-scores, FFMI increase 0.24 SD and FMI increase 0.18 SD per 1-SD increase in BW, respectively. CONCLUSION: Our results are in contrast with previous findings that birth weight is more consistently associated with subsequent lean mass than with fat mass. Associations, detected only in boys, may be explained by sex differences in sensitivity to early life environments.

The association of sex of co-twin and birth size in twins born in Yucatan, Mexico between 2008 and 2017.

Background: Birth measures of twins are potentially influenced by sex of co-twin.Aim: To analyse the association between sex of co-twin and birth weight, length and ponderal index in twin infants from Yucatan, Mexico.Subjects and methods: A total of 2057 twin pairs born during 2008-2017 were analysed. Female-female (F-F), male-male (M-M) and male-female (M-F) twin pair types were defined. Multiple linear regression models were used to analyse the association of (1) being female from M-F pairs and birth measures among overall female infants (M-F and F-F), and (2) being male from M-F pairs and birth measures among overall male infants (M-F and M-M). The length of gestation and mothers' age and level of education were used as covariates.Results: Models showed that being male from M-F pairs was associated with increases of 81 g in birth weight and 0.61 cm in length, compared to males from M-M pairs, and being female from opposite-sex pairs was associated with increases of 0.36 cm in length, compared to females from same-sex pairs.Conclusions: Males from M-F pairs show greater birth size than males from same-sex pairs, which supports the hypothesis that birth measures of twins are influenced by sex of the co-twin.

Birth weight, birth order, and age at first solid food introduction influence child growth and body composition in 6- to 8-year-old Maya children: The importance of the first 1000 days of life.

OBJECTIVES: To analyze the relationship of birth weight, birth order, breastfeeding duration, and age of introduction of solid foods with height, fat mass, and fat-free mass in a sample of Maya children when aged 6 to 8 years old. METHODS: We collected data on anthropometry, body composition, children's birth weight, birth order, early feeding practices, and household socioeconomic characteristics in a sample of 260 Maya children aged 6 to 8 years living in Merida and Motul, two cities in Yucatan, Mexico. Multiple regression models were performed to identify variables associated with height-for-age (HAZ), fat mass index (FMI), and fat-free mass index (FFMI). The predictors included in the models were birth weight (kg), birth order, duration of breastfeeding (months), age at introduction of solid foods (months), maternal age (years), and height (cm). Models were adjusted for the influence of children's age and sex, maternal educational level, and household overcrowding. RESULTS: HAZ was positively associated with child birthweight and maternal height and age, but inversely associated with birth order and age of introduction of solid foods. FMI was positively associated with birth weight, maternal age, and height, and negatively associated with birth order. FFMI was positively associated with maternal age and birth weight. CONCLUSIONS: These results are evidence of the importance of the first 1000 days of life for the growth and body composition of Maya children and contributed to understand the development of nutritional dual burden in this population.

Body Mass Index in Mother and Child Dyads and its Association With Household Size and Parents' Education in 2 Urban Settings of Yucatan, Mexico.

BACKGROUND: Overweight/obesity (OW/OB) coexists in mother-child dyads. However, a dearth of evidence on the factors associated with this phenomenon calls for research. OBJECTIVE: To analyze the association of sociodemographic factors with OW/OB in a sample of 260 Maya mother-child dyads from Yucatan, Mexico. METHODS: During 2011 to 2014, we measured height and weight in children and their mothers and calculated their body mass index (BMI). The OW/OB cutoff points were defined, for mothers, as having a BMI >25 kg/m2 and, for children, as having a BMI-for-age >2 standard deviation of the World Health Organization references. Mother-child dyads were grouped according to their BMI status: (1) normal weight mother and child, (2) normal weight mother and OW/OB child, (3) OW/OB mother and normal weight child, and (4) OW/OB mother and child. A multinomial logistic regression model was used to analyze the interrelationships among BMI status in mother-child dyads, household size, and parental education. RESULTS: Overweight/obesity coexisted in 40% of dyads. Compared to normal weight dyads (1), each unit increase in household size and in years of maternal education decreased the risks of the coexistence of OW/OB in mother-child dyads (odds ratio [OR] = 0.72, 95% confidence interval [CI] 0.55-0.94, P = .015; OR = 0.70, 95% CI 0.52-0.94, P = .019, respectively). Conversely, each year increase in paternal education increased the risk for OW/OB in dyads (OR = 1.47, 95% CI 1.08-1.99, P = .015). CONCLUSIONS: Results suggest that household size and parental education contribute to shape BMI-based nutritional status in this sample of mother-child dyads.

Body proportionality and adiposity are not related in 6- to 8-year-old Yucatec Maya children.

OBJECTIVE: The aim of this study was to analyze the association between relative leg length (RLL) (leg length × 100/height) and adiposity in a sample of 6- to 8-year-old children of Maya ancestry from Motul and Merida, Mexico. METHODS: This cross-sectional study included 260 children (128 girls) measured between 2011 and 2015. The RLL was used as a measure of body proportionality. Linear regression models were performed to examine the association between RLL (predictor) and three adiposity indicators (outcome variables): fat mass index (kg/m2 ), waist circumference (z-score), and sum of triceps and subscapular skinfolds (z-score). RESULTS: The prevalence of stunting was 12%, and a higher prevalence (19%) of short RLL (leg stunting) was found. The prevalence of overweight and obesity were 16% and 20%, respectively, but the highest prevalence was found for abdominal obesity (40%). None of the adiposity indicators were related to RLL (P > .05), even after adjusting for the influence of children's sex and age. CONCLUSIONS: Our results suggest that the coexistence of short RLL and high body adiposity is not observed in all populations. Our findings do not discount the possibility that a negative association between RLL and adiposity is expressed at older ages.

Caesarean birth and adiposity parameters in 6- to 8-year-old urban Maya children from two cities of Yucatan, Mexico.

OBJECTIVES: The purpose of this study was to analyze the association between birth mode and fat mass index (FMI = fat mass [kg]/height [m]2 ), and z-score values of waist circumference (WCZ) and sum of triceps and subscapular skinfolds (SumSkfZ) in a sample of 256 6- to 8-year-old urban Maya children from the cities of Merida and Motul in Yucatan, Mexico. METHODS: From September 2011 to January 2014, we measured height, weight, waist circumference and skinfolds in children, and height and weight in their mothers. Body composition was estimated in both generations through bioelectrical impedance analysis. Data on children's birth mode and birth weight were obtained from birth certificates. A pre-validated questionnaire for mothers was used regarding household living conditions. Multiple regression models were used to analyze the association between birth mode and adiposity parameters, adjusting for the effect of place of residence, household crowding index, children's birth weight, and maternal fat mass. Separate regression models were run for boys and girls. RESULTS: Caesarean-born children comprised 43% of the entire sample. Caesarean section (CS) was found to be associated with higher values of body adiposity in girls, but not in boys. Specifically, our models predicted that girls born by CS had an increased value of 0.817 kg/m2 in FMI and showed higher SDs values for WCZ and SumskfZ (0.29 and 0.32 SD, respectively) than girls who were delivered vaginally. DISCUSSION: Our results support the hypothesis that CS is associated with increased levels of adiposity in childhood, but only in girls.