Seasonal Changes in Birth Weight in a Semi Urban Community in the Gambia: A 4 Year Retrospective Study and Lessons for the Future

Objective: Birth weights are determined by several factors, including seasonal changes in host behavior, environmental and maternal factors. Human birth seasonality can impact on the pattern of diseases and demand on the health system. The objective of this retrospective study was to review the pattern of birth weight of babies born in a community health centre over a period of four years. Materials and Methods: A four year retrospective study of live singleton births at Fajikunda Health centre from 2007 to 2010. Data that included birth weight, gender, age and parity of mother were obtained from the records of the health centre. Statistical analyses were done using random effects model. Results: There were 8521 live singletons births over the four years, 4402 (51.7%) males and 4119 (48.3%) females. The proportion of low birth weight (<2500 g) in the population was less than 5% of the total singleton births per year. Strong evidence of monthly variation in birth weight was found after adjusting for year, parity, gender, mother`s age and date of birth (month/ year) specific error terms (p<0.0001). Birth weight was higher from May to September and reached peak in May to July. The average birth weight declined progressively over the four years (p<0.001): from 2007 to 2008 (p=0.99), 2008 to 2009 (p=0.03) and from 2009 to 2010 (p=0.06). Birth weight increased by 127.3 (95% CI: 107.2; 147.6) g per unit increase in parity up to the 5th and the decreased (p<0.0001). Average birth weight of female babies was 114.1 (93.3; 135.0) g lower than the males (p<0.0001). Mother’s age was not associated with birth weight. Conclusion: We have observed a progressive decline of birth weight with a striking seasonal variation in The Gambia. Further understanding of the reasons behind these changes is required to guide programmes and interventions.