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Factors affecting human placenta and birth weights and vitality of newborns in a subtropical environment^*

C.J. Wilcox^I; H.H. Head^I; R.M. Abrams^II

^IDepartment of Dairy and Poultry Sciences, University of Florida, Gainesville, FL 32611-0920, USA. Send correspondence to C.J.W.
^IIDepartment of Obstetrics and Gynecology, University of Florida, Gainesville, FL 32611-0920, USA

ABSTRACT

Factors affecting birth and placenta weights and vitality of human newborns in Florida were evaluated in data sets of 1480 (data set I) and 788 cases (data set II). The latter set was a subset of the first, having fewer cases because of more rigid screening procedures. Screening deleted fetuses that were not alive at birth, or had extremely high or low values for any response variable; the latter were assumed to represent abnormal cases. Factors evaluated significantly affected the response variables in most cases, but not necessarily in both data sets. In data set II, month effects were detected on all variables except vitality at 5 min postpartum (Apgar score II). Placenta weights were 112 g lower in warm than in cool months. Vitality at 1 min postpartum (Apgar score I) was affected by month but not in a systematic manner. Males were 45 g heavier for placenta, 142 g for birth and 187 g for total weights. Ethnic group affected all responses except placenta weight. Parity effects were detected for all responses except placenta weight and Apgar score II; gestation length affected all responses except placenta weight. Placenta and birth weights were highly correlated with their sum (part-whole correlation), but not with each other; nor were weights correlated with Apgar scores. Apgar scores were highly correlated with each other. Knowledge of characteristics of response variables and the factors influencing them should contribute considerably to overall knowledge of factors affecting characteristics of human births.

Keywords: human placenta; birth weights; vitality; newborns; subtropical environment.

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* Florida Agricultural Experiment Station Journal Series No. R-03756.