How many days does a mouse gestate? - briefly
A mouse pregnancy lasts roughly 19–21 days, with an average of about 20 days. This gestation period applies to common laboratory strains such as Mus musculus.
How many days does a mouse gestate? - in detail
The gestation period for a typical laboratory mouse (Mus musculus) averages 19 to 21 days, with most litters born around day 20. This interval is consistent across most strains of the house mouse, although minor variations occur: some inbred lines may complete pregnancy in 18 days, while outbred populations can extend to 22 days.
Key factors influencing the exact length include:
- Strain genetics: Inbred strains (e.g., C57BL/6) often show tighter gestational timing than heterogeneous stock.
- Maternal age: Younger females may experience slightly shorter pregnancies; advanced age can add 1–2 days.
- Environmental conditions: Ambient temperature, photoperiod, and nutrition affect hormonal regulation of parturition.
- Litter size: Larger litters sometimes trigger earlier delivery, whereas very small litters may prolong gestation marginally.
Developmental milestones during this interval are well documented:
- Days 0‑3: Implantation of the blastocyst into the uterine wall.
- Days 4‑7: Formation of the embryonic disc and early organogenesis.
- Days 8‑14: Rapid growth of limb buds, neural tube closure, and differentiation of major organ systems.
- Days 15‑19: Maturation of the respiratory and digestive systems, hair follicle development, and preparation for birth.
Comparatively, the gestation of a rat (Rattus norvegicus) spans 21‑23 days, while larger rodents such as guinea pigs require 59‑72 days, illustrating the correlation between body size and prenatal duration.