Diagnostic value of the fertilizable coitus date for the estimations of fetal age

Abstract

With the purpose of evaluating the date of the fecundating coitus for estimating fetal age, under the hypothesis of its high predictive capability, a cohort of 243 pregnant women being controlled at the primary care medical center of the city of Viña del Mar, in Chile, were studied. Each pregnant woman had three fetal age appraisals: the first, between the dates of fecundating coitus and last menstruation, the second, by means of precocious ecography, and the third, considered as the age of reference, was obtained from the newborn by means of the Extended Ballard examination. Correlation and concordance analyses between the determinations and between these and the frame of reference were performed; thereafter, a model of ordinal logistic regression was applied to establish the level of diagnostic precision. It was observed that the fetal age according to fecundating coitus is in close correlation with the age of reference (r=0.84) and even more when the woman presents a date of the last reliable.menstruation (r=0.90). Upon comparative analysis, the diagnostic value of the studied date does not significantly differ from that of the precocious ecography (p=0.19). The logistic regression equation reaches a sensibility of 86% and a specificity of 94% in the presence of a reliable date of last menstruation. The conclusion is that the date of the fecundating coitus is a semiological resource useful for estimating fetal age; its precision is comparable to the first three-month ecography of pregnancy, for which reason its incorporation to routine obstetric anamnesis is recommended.