How long does pregnancy last in mice? - briefly
Gestation in mice lasts approximately 19–21 days.
How long does pregnancy last in mice? - in detail
Mice reach full term after approximately 19–21 days of gestation. The exact period varies slightly among strains; for example, C57BL/6 females commonly deliver on day 20, while BALB/c individuals may give birth on day 21.
Key factors influencing the length of pregnancy include:
- Genetic background: Different inbred lines exhibit consistent, strain‑specific gestational lengths.
- Maternal age and parity: First‑time mothers often have a marginally shorter gestation than experienced females.
- Environmental conditions: Ambient temperature, photoperiod, and diet can shift the timing by one to two days.
- Hormonal status: Levels of progesterone and estrogen around implantation affect the progression of pregnancy.
Embryonic development follows a predictable schedule within this window:
- Days 0–3: Fertilization and entry into the oviduct; cleavage stages occur.
- Days 4–6: Blastocyst formation and implantation in the uterine wall.
- Days 7–10: Organogenesis begins; limb buds and primary brain structures appear.
- Days 11–14: Rapid growth of fetal tissues; formation of the circulatory system and skeletal elements.
- Days 15–18: Maturation of organ systems; lungs develop surfactant-producing cells.
- Days 19–21: Final growth, preparation for parturition; pups acquire fur and reflexes.
Researchers determine gestational age by counting days post‑coitum (the day of observed mating) or by assessing embryonic morphology through ultrasound or dissection. Accurate timing is essential for experimental protocols that require embryos at specific developmental stages.
In summary, the murine gestation period spans roughly three weeks, with minor variations driven by genetics, maternal condition, and environmental factors. Understanding these nuances enables precise experimental planning and reliable interpretation of developmental data.