How do mice give birth? - briefly
Female mice complete a gestation of roughly 19–21 days and then give birth to a litter of 5–12 pups via a brief vaginal delivery. The newborns are hairless, blind, and achieve independence within a few weeks.
How do mice give birth? - in detail
Mice reproduce through a rapid gestational cycle that culminates in the delivery of multiple offspring. After mating, fertilized eggs travel to the uterus, where implantation occurs within 4–5 days. The gestation period lasts approximately 19–21 days, during which the embryos develop in separate placental sacs. Hormonal shifts, primarily rising progesterone followed by a surge of estrogen and oxytocin, trigger the onset of labor.
The birthing sequence proceeds in three stages:
- Preparation (first stage) – Cervical dilation begins as uterine contractions intensify. The mother may exhibit nesting behavior, gathering bedding material to create a secure environment for the litter.
- Expulsion (second stage) – Each pup is delivered head‑first, followed by the placenta (the afterbirth). The mother typically gives birth to 5–12 young per litter, though litter size can vary with strain and environmental conditions. Contractions occur at intervals of 2–5 minutes, allowing the mother to clear each newborn and its associated membranes.
- Post‑delivery (third stage) – The dam cleans the pups, stimulates respiration by licking, and initiates nursing. Oxytocin release sustains uterine contraction, reducing postpartum bleeding and aiding involution of the reproductive tract.
Neonatal mice are altricial: they are born hairless, blind, and dependent on maternal care. The mother’s milk provides essential antibodies and nutrients for the first two weeks, after which the young begin to wean. The entire reproductive process is tightly regulated by endocrine feedback loops, ensuring efficient turnover and high reproductive output in laboratory and wild populations.