How long is a mouse pregnancy? - briefly
The gestation period of a mouse is approximately 19 – 21 days. This brief interval enables the species to produce multiple litters each year.
How long is a mouse pregnancy? - in detail
The gestation period of the common laboratory mouse (Mus musculus) lasts approximately 19 to 21 days from conception to birth. This interval can vary by a few days depending on genetic strain, maternal age, and environmental conditions.
Typical developmental milestones during this interval are:
- Days 1‑3: Fertilization and early cleavage; embryos travel to the uterus.
- Days 4‑7: Implantation of blastocysts; formation of the placenta begins.
- Days 8‑12: Organogenesis; rudimentary limbs and sensory structures appear.
- Days 13‑15: Rapid fetal growth; hair follicles develop, and the heart reaches functional maturity.
- Days 16‑18: Final maturation of lungs and nervous system; fetal movements become observable.
- Days 19‑21: Parturition; pups are born altricial, blind, and hairless.
Factors influencing the exact length include:
- Strain differences – for example, C57BL/6 mice often gestate closer to 20 days, whereas outbred CD‑1 mice may complete gestation in 19 days.
- Maternal parity – first‑time mothers sometimes experience slightly longer pregnancies.
- Ambient temperature – cooler environments can extend gestation by up to one day, while optimal housing (≈ 22 °C) supports the standard range.
- Nutritional status – severe caloric restriction may delay delivery, whereas adequate feeding maintains typical timing.
Detectable signs of pregnancy appear around day 7, when the vaginal opening becomes enlarged, and by day 14, abdominal distension is evident. Ultrasonography can confirm fetal presence as early as day 10, providing a non‑invasive method to monitor development.
Proper husbandry during the gestational window includes:
- Providing nesting material to facilitate nest building.
- Maintaining a stable, low‑stress environment to prevent premature labor.
- Supplying a balanced diet enriched with protein and essential micronutrients to support fetal growth.
Understanding the precise duration and associated variables is essential for experimental planning, timing of interventions, and ensuring animal welfare throughout the reproductive cycle.