How to know if a mouse is pregnant? - briefly
A pregnant mouse displays a rounded, enlarged abdomen, often with a faint pregnancy line, and gains noticeable weight within a week. Additional indicators include increased nesting activity and reduced locomotion.
How to know if a mouse is pregnant? - in detail
Pregnancy in a mouse can be identified through a combination of physical observations, behavioral cues, and, when necessary, diagnostic techniques.
During the early stage (days 3‑7 after mating) external signs are subtle. By the second week the abdomen begins to enlarge noticeably; the belly becomes rounder and the fur over the ventral area may appear stretched. This abdominal distension progresses steadily, reaching its maximum shortly before parturition.
Nipple development provides a reliable indicator. Around day 10 the mammary glands enlarge, and the nipples become pink and more prominent. In non‑pregnant females the nipples remain small and inconspicuous.
Weight gain follows a predictable pattern. A healthy adult female typically increases body mass by 2‑3 grams per day after implantation, with total gain of 6‑10 grams by the end of gestation. Consistent weighing on a calibrated scale can confirm this trend.
Behavioral changes often accompany gestation. Expect reduced activity, increased nesting behavior, and a preference for secluded, warm locations. Females may gather bedding material and construct a nest in the corner of the cage.
When visual assessment is ambiguous, palpation can be employed. Between days 12‑14, a trained handler can gently feel the uterus through the abdominal wall; a firm, elongated mass indicates developing embryos. Palpation requires careful technique to avoid injury.
Ultrasonography offers definitive confirmation. A portable high‑frequency probe can visualize embryos as early as day 8, revealing fetal heartbeats and number of conceptuses. This method is non‑invasive but requires specialized equipment and expertise.
Record keeping of mating dates is essential. Knowing the exact time of copulation allows calculation of the gestational window, facilitating timely observation of the aforementioned signs.
In summary, detecting pregnancy in a mouse involves monitoring abdominal enlargement, nipple growth, weight increase, nesting behavior, optional palpation, and, if needed, ultrasound imaging, all anchored to accurate breeding records.