To begin, obtain a swim-trained euthanized pregnant rat. Using a surgical knife, make an incision in the lower abdomen to expose the uterus completely. With forceps and scissors, carefully open the uterus to reveal the fetuses and placentas.
Gently peel away the surrounding amnion, preventing any harm to the fetuses. Sequentially, separate fetuses and placentas by their anatomical positions. Using sterile gauze, clean the fetus to eliminate any blood and mucous.
Then, weigh the fetus and the placenta. Next, observe the distance between the anus and genitalia. And document the gender, as well as the total number of male and female fetuses.
Unfold the curled up fetus. And using a caliper, measure the length while the fetus is lying flat.
