A Morphological Observation on Maturation of Fetal Ovary

Abstract

To evaluate the maturing process of female gonad during the intrauterine life, a light microscopic study was made based on 71 normal human ovaries ranging in gestational age from 16 to 40 weeks. These fetuses were the products of induced deliveries and all were proven by autopsy to have no associated disease or congenital malformation. Following observations were made: 1. Between gestation ages of 16 to 17 weeks the ovaries were characterized by a diffuse grouping of undifferentiated germ cells and scattered oogonia that occasionally showed first maturation division. At this period the ovary was very much reminiscent of dysgerminoma of adult ovary under lower power microscopy. 2. Secondary cortex became apparent by 18 to 22 weeks of gestation. and oogonia showed active maturation division and began to have primordial follicles. All stages of leptotene, zygotene and pachytene were seen in this period. 3. The primordial follicles were increased in number rapidly during 23 to 28 weeks, and the maturation became less active. Occasional primary follicle was seen in this period. ~. During 29 to 32 weeks the nuclei of primordial follicles were most in dictyoterie stage, and there appeared gradual increased in the number of primary follicles at the zone between secondary cortex and medulla. 5. From 33 weeks on, the secondary cortex of the ovary was gradually replaced by fibrous connective tissue with primordial and primary follicles underneath, thus first showing st igmata of adult ovary