Dynamics of uterine and ovarian size in healthy girls during the first 13 months of life according to ultrasound data

The growth and development of the uterus and ovaries in young girls can impact subsequent reproductive function. Ultrasound features of the pelvic organs and  size reference values have been described in detail in older girls, while data for first year of life are extremely limited.

Objective: To assess the size of the uterus, ovaries, and follicles and their growth dynamics in healthy girls during the first 13 months of life based on ultrasound data.

Materials and Methods. Pelvic ultrasound was performed in 342 healthy girls aged 2 days to 13 months using standard techniques and linear multifrequency transducers. Uterine and ovarian volume (cm³) was calculated using the ellipse formula: 0.523 x length x width x thickness (cm).

Results. The uterus was visualized in 100% of the examined girls, both ovaries were visualized in 79%. The median uterine length (including the cervix) was 29 mm (min–max 13–45 mm); ovary length was 13 mm (min–max 8–32 mm). The dynamics of the sizes changes of the uterus and ovaries in girls differed during the first year of life: the volume of the uterus was maximum immediately after birth, by 3 months it decreased by approximately 2 times and remained at this level until the end of the observation period; the volume of the ovaries increased after birth, reaching a maximum at 2 months, after which it decreased by approximately 2 times by 4 months and remained at this level (with minor variations) until the end of the observation period (13 months). The dynamics of changes in the maximum follicle size followed the dynamics of the ovarian volume, but with a smaller amplitude. In each ovary, from 1 to 10 follicles were determined per section (Me – 3). The median maximum follicle size in the right ovary was 5 mm (min–max – 2–16 mm), while in the left ovary it was 4 mm (min–max – 2–19 mm). No differences in the sizes of the uterus, ovaries, or follicles were found between breastfed and formula-fed girls.

Conclusions. Uterine size in girls normally reaches its maximum immediately after birth and decreases significantly by two months of age. Conversely, ovarian and follicular sizes increase significantly by two months of age, decreasing to baseline by four months. This may reflect temporary activation of the hypothalamic-pituitary system after birth. Feeding type does not affect the size of girls' pelvic organs during the first year of life. Reference values for uterine, ovarian, and follicular sizes in healthy girls can be used in clinical practice to differentiate between physiological and pathological conditions.

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