Fetal Growth of a Cow

A cow's gestation period lasts approximately 280 days, according to pettalk.com. In a little over nine months, the fetal cow grows from two cells to the soon-to-be full-sized calf.

  1. Size of the Fetus

    • During the first month, the fetal cow is smaller than your fingernail. The second month the fetus will grow to be the size of a mouse and the third, the size of a rat. By the fourth month the baby cow is the size of a small cat. At the fifth month of gestation, it is the size of a large cat. By the sixth month it has reached almost birth size, or the size of a beagle dog, according to the University of Florida (UFL).

    Position in the Uterus

    • From days 35 to 50 the fetus is settled on the pelvic floor. On day 60, it can be found in the pelvic/abdominal region. During days 90 to 150 the fetus is securely in the abdomen, says UFL.

    Uterine Diameter

    • The uterus grows from what UFL calls "slightly enlarged" at 35 days to 18 cm at 150 days. Eighteen cm is less than the size of a 12-inch ruler, for perspective.

    Palpable Structures

    • UFL lists that at 35 days the uterine asymmetry/fetal slip will be palpable and at 60 days so will the membrane slip. At 60 days, the fetus can be felt (10 to 15 cm.). After 120 days, placentomes and fremitis (ability to feel with the touch of the hand) vibrations and pulsing of the uterine artery is probable.

    Position of Calf at Birth

    • Within the first two to six hours of labor, the calf rotates into an upright position and uterine contractions begin. The mother cow's water breaks. With the cow typically lying down, the fetus enters the birth canal and the calf's feet and head protrude first. Delivery usually takes one hour or less, says the University of Missouri.