Regional development of the human epidermis in the first trimester embryo and the second trimester fetus (ages related to the timing of amniocentesis and fetal biopsy).

The epidermis was sampled from multiple body sites of whole human embryos and fetuses of 45- and 65-days, 16- and 21-weeks estimated gestation age to determine whether a regionally dependent, variable rate of interfollicular epidermal development exists. Surface characteristics and thickness of the epidermis were evaluated by scanning electron and light microscopy, respectively. It was concluded that all epidermal development proceeded simultaneously during the first trimester with the exception of the foot which was more advanced in both thickness and state of differentiation. During the second trimester the epidermis of both the head and the foot showed more precocious development, particularly in relation to the special sense organs and to the plantar surface. The interfollicular epidermis of the majority of the body, however, was approximately equivalent in the state of development. These data have potential relevance to prenatal diagnosis of inherited skin disease from amniocentesis and/or fetal biopsy specimens; the present survey of the total epidermal surface will allow one to predict the types of skin-derived cells that should be present in the amniotic fluid at a given age, and to evaluate a fetal biopsy from one region and be confident that it is an accurate index of fetal skin development, age and status in general.