How long does a mouse gestate a baby? - briefly
The gestation period for a typical house mouse lasts about 19–21 days. Litters usually consist of 5–10 offspring.
How long does a mouse gestate a baby? - in detail
The gestation of a laboratory mouse typically lasts between 19 and 21 days, with 20 days representing the average duration under standard conditions. This interval is measured from the moment of copulation to the birth of the first pup.
Several variables can shift the timeline:
- Strain differences: Inbred lines such as C57BL/6 often complete pregnancy in 19–20 days, whereas outbred strains like CD‑1 may extend to 21 days.
- Ambient temperature: Housing at 22 °C–24 °C promotes the standard period; lower temperatures can prolong development by up to two days.
- Maternal nutrition: Adequate protein and calorie intake maintains the typical length; severe restriction can delay parturition.
- Age of the dam: Young females (4–6 weeks) may exhibit slightly shorter gestations, while older breeders (>12 months) sometimes experience modest extensions.
- Litter size: Larger litters tend to be born toward the upper end of the range, whereas small litters may emerge a day earlier.
Embryogenesis proceeds through well‑defined stages within this window:
- Pre‑implantation (days 0‑4) – fertilized oocyte undergoes cleavage, reaches blastocyst, and implants in the uterine wall.
- Organogenesis (days 5‑14) – primary organ systems form; heart beats by day 8, limb buds appear by day 9.
- Fetal growth (days 15‑20) – rapid increase in body mass, fur development, and lung maturation; pups acquire the ability to thermoregulate shortly before birth.
The birthing process, called parturition, usually occurs during the early dark phase. The dam typically delivers a litter of 5–8 pups, though numbers can range from 2 to 12 depending on strain and parity.
In summary, under controlled laboratory conditions the pregnancy of a mouse spans roughly three weeks, with precise length governed by genetic background, environmental factors, and maternal health.