How long is the gestation period for mice? - briefly
The gestation of a mouse lasts approximately 19–21 days.
How long is the gestation period for mice? - in detail
The gestation of a laboratory mouse lasts approximately 19 to 21 days from conception to parturition. Most strains, such as C57BL/6 and BALB/c, fall within this range, although slight deviations occur among outbred lines and under different environmental conditions.
Key factors influencing the exact duration include:
- Genetic background: Certain strains exhibit consistently shorter or longer pregnancies; for example, DBA/2 mice may average 20.5 days, while Swiss Webster mice often reach 21 days.
- Ambient temperature: Housing at 20 °C versus 25 °C can shift the timeline by up to 0.5 days, with cooler environments extending gestation slightly.
- Maternal nutrition and health: Adequate protein intake and absence of stressors support the typical 19‑21‑day period; malnutrition or disease may prolong or truncate it.
- Parity: First‑time (nulliparous) females sometimes experience a marginally longer gestation compared with experienced breeders.
Embryonic development proceeds rapidly during this interval. By day 5 post‑coitum, the blastocyst implants; organogenesis begins around day 7 and is largely complete by day 14. Fetal growth accelerates from day 15 onward, culminating in the birth of 5–12 pups per litter, depending on strain and maternal condition.
Researchers typically determine gestational timing by checking for a vaginal plug (considered day 0), confirming mating through sperm detection, and monitoring weight gain. Ultrasound imaging can provide real‑time assessment of fetal size and viability, allowing precise staging for experimental interventions.
Post‑natal considerations include the brief neonatal period of 21 days before weaning, during which pups remain dependent on maternal care. Understanding the exact length of pregnancy is essential for scheduling timed‑matings, synchronizing developmental studies, and minimizing variability in experimental outcomes.