How does a rat’s pregnancy progress? - briefly
Gestation in rats lasts roughly 21 – 23 days; after implantation, embryos develop quickly, and the female’s abdomen becomes markedly enlarged by the second week. Parturition follows the full gestational period, producing a litter of typically six to twelve pups.
How does a rat’s pregnancy progress? - in detail
The gestational period of a laboratory rat lasts approximately 21 – 23 days. Development proceeds through distinct stages, each marked by specific physiological and behavioral changes.
During the first three days after mating, sperm reach the oviducts, fertilize ova, and the resulting zygotes travel to the uterus. By day 4, implantation occurs; the blastocyst embeds in the uterine lining, and progesterone levels rise sharply, supporting the nascent pregnancy.
From day 5 to day 12, embryogenesis dominates. Primary organ systems begin to form: the neural tube closes, the heart starts beating, and limb buds appear. By the end of this interval, the embryos are recognizable as distinct structures, and the placenta becomes fully functional, facilitating nutrient exchange.
The fetal growth phase spans days 13 to 20. Rapid increase in body mass is evident; the pups acquire fur, eyes open, and skeletal ossification progresses. The mother exhibits nesting behavior, constructing a secure environment for delivery. Hormonal shifts, particularly elevated prolactin and oxytocin, prepare the uterus for parturition.
Labor typically initiates on day 21. Contractions become regular, leading to the expulsion of pups in a litter that can range from 6 to 12 individuals. Post‑birth, the dam secretes milk and displays maternal care, ensuring offspring survival.
Key milestones:
- Days 0‑3: Fertilization and zygote transport
- Day 4: Implantation, progesterone surge
- Days 5‑12: Organogenesis, placenta maturation
- Days 13‑20: Fetal growth, fur development, nesting
- Day 21‑23: Parturition, lactation onset
Understanding this timeline aids researchers in timing interventions, assessing developmental toxicity, and optimizing breeding protocols.