Staging and ageing of mammalian embryos and fetuses according to Štěrba

Based on morphological staging according to Štěrba it is possible to estimate the gestation age of mammalian embryos and fetuses. It is also possible to compare the prenatal developmental levels in mammals with a different gestation period.

First step: Find out the developmental stage of the embryo or fetus according to the following table:

  • SCS 1: primitive streak
    •
  • SCS 2: first somites (1-7)
    •
  • SCS 3: limb buds, tail bud, 4 branchial arches, closed otic vesicle
    •
  • SCS 4: eye pigmented, handplate present, lens vesicle separated from ectoderm, hemispheres of forebrain
    •
  • SCS 5: marked pinna, handplate indented, compact lens, follicles of tactile hairs on the upper lip
    •
  • SCS 6: palate fused, toes separated, onset of ossification, hair follicles all over the body surface
    •
  • SCS 7: eyelids fused, reposition of umbilical hernia
    •
  • SCS 8: skin wrinkled
    •
  • SCS 9: eruption of tactile hairs on the upper lip, birth stage in nidicolous mammals
    •
  • SCS 10: eruption of hairs all over the body surface
    •
  • SCS 11: eyelids separated
    •
  • SCS 12: birth stage in nidicolous mammals
    •

(top)

Second step: Calculate the gestation age

Find the gestation period for the studied mammalian species on the x-axis. Go vertically upwards and find the SCS (Štěrba´s comparable stage) of the studied embryo or fetus. Now go horizontally to the left and read the relative gestation period (%) on the y-axis. Calculate the absolute gestation age (days) using this value and the gestation period of the studied mammalian species. (In the figure you will find only the first nine developmental levels. Regression curves of higher levels have not been published yet.)



x-axis: total gestation period of the selected mammalian species (days), y-axis: relative gestation age of the studied embryo/fetus (% of total gestation period)

(top)

Selected references

Štěrba, O.: Prenatal development of microtine rodents. Acta Sc. Nat. Brno 10:1-41, 1976

Štěrba, O.: Prenatal development and growth of Lepus europaeus. Folia Zool. 30:147-154, 1981

Štěrba, O.: Prenatal growth and development of selected mammalian species. Theses, Czechoslovak Academy of Sciences, 1983 (in Czech)

Štěrba, O.: Staging and ageing of of mammalian embryos and fetuses. Acta Vet. Brno 64:83-89, 1995

(top)

Back to the homepage of the embryological collection