Sex dimorphism in development dynamics and in development progression of morphological features in human foetuses

The study material comprised 3889 foetuses of both sexes, aged 20–42 weeks. t-Student test has been applied to evaluate the existence of potential sex-dependent differentiation of developmental trends as assessed by weekly measurements of selected somatic features and by the weight of internal organs. The regression coefficients of the analysed variables have been compared against the opposite sex. The rate of development of the analysed features in consecutive weeks has been found to be sex-related. Highest sex-related differences have been observed for the total body weight and for the weight of internal organs, with the exception of the adrenals, and the differences have been significant enough to justify the existence of contrasting, sex-dependent patterns of development of the analysed variables. The development of the analysed morphological features has been depicted by curvilinear regression. When described by various degree polynomials the development course of the analysed features displays sex-related differences. Only the change in the weight of the adrenals is similar for both sexes. The evaluation of the developmental advancement of the analysed features has revealed that they are usually at a more advanced development level in female foetuses.