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.

Height, weight and body mass index by age and sex in children aged 4 to 6 years in Merida, Mexico, as compared to international references after normalization with LMS.

A cross-sectional study was done in 2006-2007 of 458 children (218 boys and 240 girls) aged 4 to 6 years (range 4.00 to 6.99 years) in Merida, Mexico. Height (cm) and body weight (kg) were measured to estimate growth; body mass index (BMI, kg/m2) was calculated to evaluate nutritional status. Results showed significant sex difference with respect to height, weight, and BMI. Increment of height and weight with age was observed. However, age difference in BMI was not consis- tent. Nutritional status was evaluated using International Obesity Task Force (IOTF) classification and BMI cut-off values showed notable rates of overweight (boys 14.41% and girls 17.75%) and obesity (boys 12.43% and girls 7.21%). Anthropometric data of height, weight, and BMI were normalized using LMS methodology and were compared with World Health Organization (WHO) growth reference data. Again, increment of height and weight with age was observed although those were lower in the present study for boys and girls than the corresponding WHO growth reference data. In contrast, mean BMI by age in the present results exceeded WHO reference data, especially above the 85th percentile. Assessment of nutritional status with reference to IOTF and WHO revealed similar trends.

Estimation of stature from upper arm length in children aged 4.0 to 6.92 y in Merida, Yucatan.

OBJECTIVE: To understand age-sex variation of stature and upper arm length (UAL) and to estimate stature from UAL through prediction equations. METHODS: A cross-sectional study was undertaken in 2006-2007 among 458 children (218 boys and 240 girls) aged 4.0 to 6.92 y of south Merida in Yucatan, Mexico. RESULTS: The results show significant age variation (p < 0.001) of stature and upper arm length (UAL) in children. Boys show significantly higher mean stature and UAL compared to the girls. Relative proportion of upper arm length to stature is greater in boys. Interrelationship between stature and upper arm length exhibits significant association with respect to age and sex of children. Reconstruction of stature from upper arm length through regression analysis also gives good prediction models for separate and combined samples of both sexes with age. Regression coefficients for UAL predicting stature account for 0.90 or greater variance in the dependent variable (stature). The difference between reconstructed stature and the actual measurement is less than ±2.00 cm. CONCLUSIONS: UAL appears to be a reliable indicator to estimate stature in children aged 4.0 to 6.92 y old.

Does a seasonal developmental rhythm exist in tropical living populations?

The main aim of this work concerns the answer a question whether the general regularity of seasonal differences in changes of height, weight and body components during ontogeny exist. If so, whether this phenomenon depends on cyclic changes in nature or this rather is an adjustment to local conditions and mode of life. To answer this question the studies took place in the tropical climate of Yucatan and included 49 boys and 47 girls aged 11-12 years and being of the Maya, Mestizo and Creole origin. The youths were attending two schools which were located in rather poor districts of Merida (capital city of the Yucatan State, Mexico). The investigations started in February 2002 and ended in November 2003 and were continued monthly. The standard anthropometric methodology was applied to measure body height, weight, arm, waist, hip and calf circumferences and five subcutaneous fat folds (biceps and triceps brachii, subscapular, suprailiac and calf). Bioimpedance techniques were used to measure fat mass (FM), fat free mass (FFM) and total body water (TBW). The results show that monthly or longer rates of stature increments and increments or declines of body mass do not exist. The similar observations were mentioned according to daily studies of similar type in literature. There are not similar regularities of changes even in groups of coevals of the same gender and within the youths coming from the same district. Each variable shows a quite specific rate of changes.