Seasonality and other variation trends in birth weights of 4000g and above: A preliminary report from the University of Port Harcourt Teaching Hospital, Nigeria.

Abstract

BACKGROUND: Anecdotal evidence appears to suggest a progressive increase in the proportion of large babies born at the University of Port Harcourt Teaching Hospital (UPTH), Nigeria. The objective of this study is to examine retrospectively the profile of birth weights at the UPTHover a defined time frame. METHODS: The birth weights of all babies born in the hospital from January 1, 1990 to December 31, 1999 were analyzed with the focus on weights = 4000g. The ten-year period was elongated into 20 six-monthly observation points and the periodic fluctuations in the proportion of birth weights = 4000g smoothed by using exponentially weighted moving averages with a weighting factor of 0.18. Seasonal variations in rates of birthweight = 4000g were calculated using Ratchet Circular Scan Test for a short seasonal peak. Proportions were compared using chi-square statistic. RESULTS: Fourteen thousand three hundred and seven birth weights were recorded; 7111 males and 7196 females. Nine hundred and four (12.7%) and 434 (6.0%) of males and females respectively were 4000g and above. There was a sustained increase in the proportion of the = 4000g category during the observation period although the slope was steeper among the males (slope with [95% Confidence Interval] for males = 0.4131 [0.3213 to 0.5050] and for females 0.1801 [0.05565 to 0.3045]. There was a significant 3-month peak August to October of males only of birth weight = 4000g, (3-month peak; August to October, 30.3% of events. Test Statistic 3.46, p < 0.005). CONCLUSION: There has been a steady increase in the proportion of babies of birth weight =4000g at the UPTH in the ten-year period studied. This trend could be potentially dangerous for both mother and baby; therefore the authors believe it would be a good idea to carry out a prospective investigation along similar lines but using a much broader study base.