How long is a mouse’s pregnancy? - briefly
A mouse gestates for approximately 19–21 days. The exact duration can differ slightly among strains and environmental conditions.
How long is a mouse’s pregnancy? - in detail
The gestation period for a common house mouse (Mus musculus) averages 19‑21 days, with 20 days considered the standard length under controlled laboratory conditions. This interval represents the time from fertilization to parturition and is markedly shorter than that of larger rodents such as rats, whose gestation lasts about 21‑23 days.
Key factors influencing the duration include:
- Strain differences: Inbred strains (e.g., C57BL/6) may exhibit a slightly shorter gestation (≈19 days) compared to outbred stocks (≈21 days).
- Maternal age: Young females (<8 weeks) often deliver at the lower end of the range, whereas older breeders can experience a modest extension.
- Environmental temperature: Ambient temperatures below 20 °C tend to lengthen the period by 1‑2 days; higher temperatures may accelerate development but risk neonatal mortality.
- Nutritional status: Adequate protein and caloric intake support the typical timeline; severe restriction can delay parturition.
Embryonic development proceeds through distinct stages:
- Pre‑implantation (days 0‑4): Zygote cleavage, blastocyst formation, and uterine attachment.
- Organogenesis (days 5‑14): Formation of the neural tube, heart, limbs, and major organ systems.
- Fetal growth (days 15‑20): Rapid increase in body mass, hair follicle development, and lung maturation.
Litter size averages 5‑8 pups, with each gestation producing a full complement of neonates ready for suckling shortly after birth. The short reproductive cycle, combined with rapid post‑natal growth, enables mouse populations to expand quickly under favorable conditions.