Objective: To examine the relationship, if any, between the geographical season in which a baby is born and the baby's birth weight and sex.
Methods: The birth weights and sexes of 6141 babies delivered over a five- year period in a Nigerian mission hospital were prospectively recorded according to the month and year of delivery. The mean birth weights and sexes of infants born in the wet season (May to October) were compared with those of their counterparts born in the dry season (November to April).
Results: Comparison of the mean birth weight during the wet and dry seasons showed that for male infants it was 3333 (542)g versus 3197 (566)g (p<0.01), while for female infants it was 3203 (559)g versus 3110 (601)g (p<0.01). When both sexes were combined, the mean birth weights were 3249 (488)g and 3164 (524)g in wet and dry seasons respectively(p<0.01). Slightly more boys than girls were born in the dry season compared with the wet season (p>0. 05).
Conclusion: Irrespective of gender, babies born during the wet season were significantly heavier than their counterparts born during the dry season. There was a higher probability of a boy birth in the dry season.