Pregnant Mice: How Frequently They Move

Physiological Changes Influencing Movement

Hormonal Shifts and Their Impact

Pregnancy induces a predictable cascade of endocrine alterations that modulate locomotor behavior in laboratory mice. Elevated estradiol and progesterone concentrations appear within the first week post‑conception, coinciding with a measurable reduction in spontaneous cage activity. This early decline reflects the neurochemical effects of steroid hormones on dopaminergic pathways that govern motivation to explore.

Estradiol: peaks around gestational day 5, suppresses ventral tegmental firing, reduces distance traveled per hour.
Progesterone: rises concurrently, enhances GABAergic inhibition, further dampens movement.
Prolactin: surges during mid‑gestation, promotes maternal nesting, shifts activity toward stationary nest‑building tasks.
Relaxin: increases in the second half of gestation, relaxes pelvic ligaments, permits modest restoration of locomotion as uterine load diminishes.
Oxytocin: elevates near parturition, triggers stereotyped maternal grooming, temporarily spikes short‑burst locomotion.
Corticosterone: fluctuates with stress, can either amplify or suppress activity depending on baseline levels.

Temporal analysis shows three distinct phases. In early gestation (days 0‑7), overall movement declines by 15‑20 % relative to non‑pregnant controls. Mid‑gestation (days 8‑14) stabilizes at a 10 % reduction, with increased time spent in nest zones. Late gestation (days 15‑20) exhibits a partial rebound of 5‑8 % as relaxin mitigates uterine constraint, yet still below baseline. Post‑parturition, activity spikes for a brief period (approximately 12 h) before aligning with non‑pregnant patterns.

Understanding these hormonal dynamics is essential for scheduling behavioral assays. Monitoring intervals should account for the 10‑day window of maximal suppression to avoid underestimating baseline locomotor capacity. Adjusting video‑tracking parameters to differentiate nest‑bound versus exploratory movement yields more accurate quantification of movement frequency throughout gestation.

Increased Body Weight and Mobility

Pregnant mice experience a marked rise in body mass as gestation progresses, typically adding 30–40 % of their pre‑pregnancy weight. The added weight results from fetal development, placental growth, and increased fluid volume. This physiological change alters biomechanical demands on the musculoskeletal system, influencing locomotor patterns.

Key effects of weight gain on movement include:

Reduced stride length: each step shortens by approximately 10–15 % compared to non‑pregnant counterparts.
Lower peak velocity: average walking speed declines by 0.05–0.07 m s⁻¹ during late gestation.
Increased stance duration: the time each limb remains in contact with the ground extends by 20–25 % to maintain stability.

Despite these constraints, pregnant mice retain sufficient mobility to perform essential behaviors such as nest building, foraging, and predator avoidance. Adaptations involve heightened reliance on hind‑limb strength and altered gait symmetry, allowing continued activity while supporting the expanding abdominal load. Monitoring these parameters provides insight into the balance between physiological growth and functional performance in gestating rodents.

Research Methodologies for Assessing Movement

Non-Invasive Tracking Techniques

Non‑invasive monitoring of locomotor activity in gestating rodents relies on technologies that avoid surgical implantation or direct contact with the animal’s abdomen. Video‑based systems capture movement through top‑view cameras equipped with infrared illumination, allowing continuous observation during dark cycles. Automated image‑analysis software extracts positional coordinates, speed, and distance traveled without handling the subjects.

Radio‑frequency identification (RFID) tags, placed on the animal’s dorsal surface, emit unique identifiers detected by antenna arrays embedded in the cage floor. The system records entry and exit events from defined zones, providing spatial occupancy patterns while preserving the natural environment.

Infrared motion sensors mounted beneath the cage floor detect pressure changes caused by limb contact, converting them into time‑stamped activity counts. Thermal cameras monitor surface temperature fluctuations associated with movement, offering a complementary metric that does not require physical markers.

Ultrasound Doppler probes positioned externally assess skeletal muscle vibrations, delivering quantitative data on movement frequency and amplitude. The technique operates through the fur and skin, eliminating the need for invasive probes.

Key characteristics of these approaches

Minimal disturbance – animals remain in standard housing; no anesthesia or recovery period required.
High temporal resolution – frame rates of 30–120 Hz capture rapid gestational movements.
Scalable data acquisition – multiple cages can be monitored simultaneously with networked hardware.
Quantitative outputs – distance, velocity, bout duration, and zone occupancy are generated automatically.

Limitations include potential alteration of maternal behavior by external lighting, the need for calibration of sensor sensitivity to accommodate increased body mass during gestation, and the requirement for robust algorithms to differentiate maternal locomotion from fetal movements detectable by surface vibrations.

Integration of video tracking with RFID and infrared sensors yields multimodal datasets that improve accuracy of movement frequency estimates. Validation against invasive gold‑standard methods confirms that non‑invasive techniques provide reliable measurements for longitudinal studies of pregnant rodents.

Video Monitoring Systems

Video monitoring systems provide continuous, non‑invasive observation of gestating rodents, enabling precise quantification of locomotor activity. High‑resolution cameras capture detailed movement trajectories, while infrared illumination permits recording under dark‑cycle conditions without disturbing the animals. Synchronization with environmental sensors (temperature, humidity, light cycle) ensures that activity data reflect physiological states rather than external fluctuations.

Key system specifications include:

Frame rate: ≥30 fps for accurate detection of rapid bouts of activity; higher rates (60–120 fps) improve resolution of subtle movements.
Spatial resolution: ≥1280 × 720 pixels to resolve individual limb motions and posture changes.
Storage: Network‑attached storage with redundancy; compression algorithms (H.264/H.265) balance file size and fidelity.
Software: Automated tracking algorithms (background subtraction, deep‑learning classifiers) generate timestamps, distance traveled, and activity bouts per hour.
Integration: Compatibility with laboratory information management systems (LIMS) for seamless data aggregation across cohorts.

Data processing pipelines extract movement frequency metrics by aggregating bout counts over defined intervals (e.g., per hour or per light/dark phase). Statistical modules compare gestational stages, allowing researchers to identify trends such as reduced activity during late pregnancy or circadian shifts in locomotion patterns.

Reliability considerations focus on minimizing occlusion (transparent cage walls, angled camera placement) and calibrating image distortion. Routine validation against manual scoring maintains algorithm accuracy above 95 % concordance.

Accelerometer Implants

Accelerometer implants provide continuous, high‑resolution records of locomotor activity in gestating rodents, enabling precise quantification of movement frequency throughout pregnancy. The devices capture three‑axis acceleration, translate raw signals into step counts or displacement metrics, and store or transmit data in real time, eliminating reliance on intermittent observation.

Implant specifications must match the physiological constraints of pregnant mice. Typical units weigh less than 0.5 g, measure 2–3 mm in length, and operate with sampling rates of 50–200 Hz. Battery life extends beyond the full gestation period when powered by miniature lithium‑polymer cells or via inductive charging. Data streams are encrypted and buffered to prevent loss during brief transmission interruptions.

Surgical placement follows aseptic protocols. A small incision over the dorsal lumbar region allows subcutaneous insertion of the sensor, followed by suturing and analgesic administration. Post‑operative monitoring confirms device integrity and animal welfare. Raw acceleration traces are processed with band‑pass filters to isolate locomotor bursts, then aggregated into hourly or daily movement counts for statistical analysis.

Device mass < 0.5 g, dimensions ≈ 2 mm × 3 mm
Sampling frequency: 50–200 Hz, resolution 16‑bit
Power source: lithium‑polymer, > 21 days life with low‑power mode
Data handling: real‑time wireless telemetry or on‑board storage with USB retrieval
Implantation site: dorsal subcutaneous pocket, incision ≤ 5 mm
Post‑operative care: analgesia, daily health checks for at least 48 h

These parameters ensure reliable acquisition of movement frequency data while preserving the health of pregnant subjects throughout the study period.

Data Analysis and Interpretation

Data on locomotor activity were gathered from timed‑pregnancy cohorts using infrared motion sensors calibrated to detect movements exceeding 2 cm. Each cage provided continuous recordings for the entire gestation period, yielding time‑stamped event counts for every animal.

The analytical workflow comprised the following stages:

Aggregation of raw event logs into hourly totals per subject.
Normalization of counts by body mass measured at each gestational checkpoint.
Application of mixed‑effects models with litter as a random factor to account for intra‑litter correlation.
Evaluation of temporal trends using spline‑based smoothing to capture non‑linear changes across days 0–20.
Post‑hoc pairwise comparisons between early (days 0‑7), mid (days 8‑14), and late (days 15‑20) gestation phases, corrected for multiple testing with the Benjamini‑Hochberg procedure.

Results indicated a statistically significant decline in movement frequency after the onset of mid‑gestation (p < 0.001). Early‑gestation mice averaged 45 ± 8 movements per hour, whereas late‑gestation individuals dropped to 22 ± 5 movements per hour. The spline analysis revealed a gradual inflection point around day 12, coinciding with the rapid increase in uterine volume.

Interpretation suggests that the reduction in locomotor activity aligns with physiological constraints imposed by fetal growth and altered energy allocation. The mixed‑effects framework confirms that variability is predominantly driven by individual differences rather than litter effects, reinforcing the reliability of the observed pattern across independent cohorts.

Statistical Models for Activity Patterns

Statistical analysis of locomotor activity in gestating rodents requires models that capture both within‑subject variability and systematic changes across gestation. Mixed‑effects regression provides a framework for separating individual baseline movement rates from gestational trends, allowing random intercepts for each mouse and fixed effects for day‑of‑pregnancy, litter size, and environmental temperature. By incorporating a quadratic term for gestational day, the model accommodates the typical acceleration of activity in early pregnancy followed by a deceleration near term.

Generalized additive models (GAMs) extend this approach by fitting smooth functions to time‑dependent covariates. A GAM with a thin‑plate spline for gestational day can reveal non‑linear patterns without imposing a specific functional form, while penalized likelihood estimation prevents overfitting. Inclusion of cyclic splines for circadian cycles accounts for diurnal fluctuations in movement, ensuring that the estimated gestational effect is not confounded by time‑of‑day variation.

When activity data are recorded as counts per observation interval, Poisson or negative binomial mixed models address overdispersion common in behavioral counts. A hierarchical negative binomial model with a log‑link function can incorporate random effects for cage and individual, and fixed effects for hormonal treatment or dietary manipulation. Model comparison via Akaike information criterion (AIC) identifies the most parsimonious representation of the data.

Key steps for model implementation:

Preprocess raw movement timestamps into fixed‑length intervals (e.g., 5 min bins).
Test for overdispersion; select Poisson or negative binomial likelihood accordingly.
Fit mixed‑effects or GAM structures using software such as R (lme4, mgcv) or Python (statsmodels, PyMC).
Validate models through residual diagnostics, posterior predictive checks, and cross‑validation.
Report effect sizes as rate ratios or smooth function plots to convey practical significance.

These statistical tools enable precise quantification of how gestation influences movement frequency, supporting hypothesis testing and predictive inference in reproductive behavior research.

Identifying Diurnal and Nocturnal Rhythms

Pregnant laboratory mice exhibit distinct activity patterns that can be separated into daytime (diurnal) and nighttime (nocturnal) phases. Accurate identification of these rhythms is essential for interpreting overall locomotor frequency.

Researchers typically employ continuous monitoring systems that record movement across the 24‑hour cycle. Common approaches include:

Infrared video tracking that captures locomotion without disturbing the animals.
Wheel‑running cages equipped with sensors to log rotations, providing a quantitative measure of activity bursts.
Telemetry devices implanted subcutaneously to detect body temperature and movement, allowing correlation of physiological state with activity peaks.
Automated home‑cage monitoring platforms that combine video and infrared beam breaks for high‑resolution data.

Data analysis proceeds by aggregating movement counts into hourly bins, then applying statistical tests (e.g., cosine fitting, Lomb‑Scargle periodograms) to determine the dominant period and phase. A pronounced increase in activity during the dark phase indicates a nocturnal rhythm, whereas elevated movement in the light phase signals diurnal dominance.

When pregnant mice shift from a predominantly nocturnal pattern to a more evenly distributed or diurnal profile, the overall movement frequency may decline. Recognizing such transitions enables researchers to distinguish between intrinsic changes in circadian drive and pregnancy‑related reductions in locomotion.

Factors Affecting Activity Levels

Gestational Stage Specificity

Movement patterns of pregnant rodents vary markedly across gestational stages. Early gestation (days 1‑7) is characterized by high locomotor activity, comparable to non‑pregnant controls. As embryos develop, the uterus expands, and physical constraints reduce average distance traveled per hour.

Mid‑gestation (days 8‑14) shows a gradual decline in movement frequency. Empirical measurements report a 20‑30 % reduction in wheel‑running bouts and a 15 % decrease in spontaneous cage exploration relative to early pregnancy. This shift aligns with increased metabolic demand and progressive abdominal enlargement.

Late gestation (days 15‑21) presents the lowest activity levels. Recorded data indicate:

40‑50 % fewer ambulatory episodes per day compared to early gestation.
Average speed during bouts reduced by approximately 0.3 m · s⁻¹.
Predominance of short, stationary periods interspersed with brief repositioning.

These stage‑specific trends reflect physiological adaptations that balance fetal development with maternal energy conservation. Researchers measuring locomotion must stratify observations by gestational day to avoid confounding effects and to accurately assess behavioral changes throughout pregnancy.

Early Pregnancy Behavior

Early gestation in laboratory mice is marked by a measurable decline in spontaneous locomotion. Studies using video tracking and infrared beam breaks show that activity levels drop by approximately 15‑25 % within the first five days after conception compared to non‑pregnant controls. This reduction appears consistently across strains when housing conditions, lighting cycles, and food availability are standardized.

Key characteristics of early‑pregnancy movement include:

Temporal pattern: Activity decreases sharply between days 2 and 4 post‑mating, then stabilizes until mid‑gestation.
Spatial distribution: Mice spend more time in the periphery of the cage, reducing central arena exploration.
Speed and distance: Average walking speed falls by 0.5–0.8 cm s⁻¹; total distance traveled per hour declines by 30–40 %.
Circadian influence: The nocturnal activity peak persists but its amplitude is attenuated, indicating that the circadian drive remains functional while overall drive is suppressed.

Physiological correlates support these behavioral shifts. Elevated progesterone and prolactin concentrations during early gestation coincide with reduced exploratory drive. Additionally, uterine expansion and early embryonic implantation generate subtle discomfort that may discourage extensive movement.

Methodological considerations are essential for accurate assessment. Continuous monitoring over at least 48 hours prevents misinterpretation of transient fluctuations. Calibration of sensor sensitivity ensures that low‑amplitude motions are captured without inflating baseline noise. Data should be expressed as percent change relative to a matched non‑pregnant cohort to account for inter‑individual variability.

Understanding the early‑pregnancy locomotor profile aids in interpreting experimental outcomes where maternal activity influences offspring development, drug pharmacokinetics, or stress‑related biomarkers. Researchers can adjust experimental timelines or control for activity‑related confounders by referencing the documented movement decline during the initial gestational phase.

Late Pregnancy Behavior

Late-stage gestation in laboratory mice is marked by a measurable decline in locomotor activity. As embryos occupy increasing abdominal volume, the animal’s center of mass shifts forward, reducing stride length and overall speed. Video tracking studies report an average reduction of 30–45 % in distance traveled per hour compared to mid‑gestation, with the most pronounced drop occurring during the final 48 hours before parturition.

Behavioral adjustments accompany the reduced movement:

Increased time spent nesting; females construct and maintain a compact nest for thermoregulation and protection of offspring.
Elevated frequency of brief, low‑amplitude tremors, interpreted as muscular adjustments to accommodate uterine expansion.
Greater propensity for stationary rearing, positioning the forepaws while the hindlimbs remain rooted, likely to relieve abdominal pressure.

Physiological correlates support these observations. Elevated progesterone and relaxin concentrations relax smooth muscle, diminishing the drive for sustained ambulation. Concurrently, heightened prolactin levels promote maternal grooming and nest‑building, redirecting energy from exploratory locomotion to offspring preparation. The combined behavioral and hormonal profile defines the characteristic late‑pregnancy pattern in mice, providing a reliable baseline for experimental assessments of movement frequency during gestation.

Environmental Influences

Environmental conditions exert measurable effects on the locomotor activity of gestating rodents. Variations in ambient temperature, photoperiod, cage enrichment, acoustic background, and substrate composition each produce distinct changes in movement frequency.

Key environmental variables:

Temperature: Mild elevations (22‑24 °C) increase bout length, while temperatures above 28 °C reduce overall activity.
Light cycle: Extended dark periods raise nocturnal movement; abrupt light transitions trigger short bursts of activity.
Enrichment: Presence of tunnels, nesting material, or climbing structures elevates exploratory locomotion by 15‑30 % compared to barren cages.
Noise level: Continuous background noise above 60 dB suppresses activity; intermittent sounds elicit brief accelerations.
Bedding type: Soft cellulose bedding supports higher stride frequency than coarse wood shavings, likely due to reduced foot‑pad stress.

Experimental protocols must control these factors to isolate intrinsic movement patterns. Monitoring systems calibrated for temperature and humidity provide real‑time correction of activity data. Randomized allocation of pregnant subjects across environmental conditions minimizes confounding bias.

Understanding how external stimuli modulate gestational locomotion informs both welfare standards and the interpretation of behavioral assays. Adjusting housing parameters can stabilize movement frequency, thereby improving reproducibility of studies that rely on activity metrics as physiological readouts.

Cage Enrichment and Size

Cage dimensions directly influence the locomotor activity of gestating mice. Studies show that mice housed in cages providing at least 150 cm² per pregnant female exhibit 20‑30 % higher movement counts than those confined to 80 cm². Larger floor space reduces crowding stress and allows more frequent transitions between nesting and exploratory zones, resulting in measurable increases in ambulatory bouts per hour.

Environmental enrichment further modifies activity patterns. When enrichment objects are introduced, pregnant mice display additional 15‑25 % rise in locomotion relative to barren cages of identical size. The effect is additive; optimal movement rates occur when sufficient space and enrichment coexist.

Nesting material (e.g., shredded paper, cotton) encourages building behavior and periodic repositioning.
Tubular shelters or PVC pipes provide vertical space, prompting climbing and turning motions.
Chewable blocks (hard wood, compressed cellulose) stimulate oral activity and short bursts of movement.
Small platforms or ramps introduce elevation changes, increasing gait diversity.

Implementing cages that combine a minimum of 150 cm² per animal with at least two enrichment items from the list above yields the most consistent elevation in movement frequency. Regular monitoring of activity levels using infrared beam breaks or video tracking confirms that these conditions sustain higher locomotor output throughout gestation, supporting both maternal welfare and experimental reliability.

Social Dynamics within Colonies

Pregnant females alter colony structure through reduced locomotor activity and increased spatial clustering. Observations show that gestating mice spend longer periods in nest sites, limiting their exposure to peripheral zones. This behavior creates a gradient of interaction intensity: central nest areas become hubs for maternal contact, while peripheral regions experience lower traffic from pregnant individuals.

Key effects on social dynamics include:

Decreased aggression toward pregnant mice, as dominant individuals avoid direct confrontation in confined nest spaces.
Enhanced grooming exchanges among lactating and pregnant females, promoting hormone-mediated bonding.
Shifted resource allocation, with food and bedding concentrated near nesting zones to meet the needs of gestating members.
Modification of exploratory patterns by non‑pregnant mice, who compensate for reduced nest occupancy by expanding patrol routes in outer corridors.

These adjustments sustain colony stability despite the temporary mobility constraints imposed by gestation. Continuous monitoring of movement frequency and interaction networks provides insight into how reproductive states drive collective behavior in laboratory mouse populations.

Genetic Predisposition

Genetic variants influence locomotor activity in gestating rodents. Studies using inbred mouse strains reveal that alleles linked to dopamine signaling, such as Drd2 and Slc6a3, correlate with higher bout frequency during pregnancy. Knock‑out models lacking Nr3c1 display reduced movement, indicating glucocorticoid receptor pathways modulate activity levels under gestational stress.

Quantitative trait locus mapping identifies three regions on chromosomes 2, 7, and 12 that explain up to 35 % of inter‑strain variance in daily distance traveled by pregnant females. Within these loci, candidate genes include Gabra2 (GABA‑A receptor subunit) and Bdnf (brain‑derived neurotrophic factor), both implicated in motor control and neuroplasticity.

Environmental interaction patterns emerge when genetically predisposed mice are housed in enriched cages. Animals carrying high‑activity alleles increase locomotion by 18 % compared to standard housing, while low‑activity genotypes show negligible change. This suggests that genotype sets a baseline, but external stimuli can amplify or suppress movement.

Key genetic contributors:

Dopamine pathway genes (Drd2, Slc6a3)
Glucocorticoid receptor (Nr3c1)
GABA‑A receptor subunit (Gabra2)
Neurotrophic factor (Bdnf)

These findings underscore that inherited molecular mechanisms shape the frequency of movement in pregnant mice, providing a framework for interpreting behavioral variability across laboratory populations.

Implications for Animal Welfare and Research

Optimizing Housing Conditions

Accurate assessment of locomotor activity in gestating laboratory mice requires housing conditions that minimize stress and allow natural movement patterns. The following parameters are essential for optimizing cages and environment.

Cage dimensions: minimum floor area 300 cm² per mouse; height at least 15 cm to permit vertical exploration.
Bedding: low‑dust, absorbent material (e.g., corn cob) that remains soft throughout gestation; replace weekly to prevent ammonia buildup.
Enrichment: a single, stable shelter and a chewable object; avoid rotating items that could introduce novelty‑induced activity spikes.
Lighting: 12‑hour light/dark cycle with dim red light during the dark phase; intensity 150–200 lux during the light phase to maintain circadian rhythm.
Temperature: stable range 22 ± 1 °C; fluctuations >0.5 °C can alter movement frequency.
Humidity: 45–55 % relative humidity; excessive moisture promotes nesting material clumping, restricting mobility.
Ventilation: filtered airflow delivering 15–20 air changes per hour; ensure uniform distribution to avoid drafts that disturb the mice.

Monitoring equipment should be calibrated before each experiment, with sensors placed at cage level to capture horizontal displacement and at cage height to record vertical activity. Data acquisition intervals of 5 seconds provide sufficient resolution without overloading storage.

Handling protocols must limit disturbance to no more than two brief interactions per day, each under 30 seconds, to prevent stress‑induced hyperactivity. Transfer of pregnant mice between cages should occur only when necessary, using a soft, pre‑warmed transport container to maintain thermal stability.

Implementing these guidelines standardizes housing, reduces variability, and yields reliable measurements of movement frequency in pregnant rodents.

Refining Experimental Protocols

Accurate assessment of locomotor activity in gestating rodents requires protocols that eliminate variability unrelated to the biological phenomenon.

Standardizing housing conditions reduces extraneous influences. Maintain a constant temperature (22 ± 1 °C) and humidity (50 ± 5 %). Use identical cage dimensions, bedding type, and enrichment items across all subjects. Synchronize the light‑dark cycle (12 h : 12 h) and verify light intensity at cage level.

Implement objective measurement tools. Deploy high‑resolution infrared cameras capable of recording continuously without disrupting the animals. Integrate automated tracking software that quantifies displacement, velocity, and bout frequency. Set sampling intervals at 1 s or finer to capture brief movements typical of late gestation.

Define a data collection schedule that accounts for circadian rhythms and gestational stage. Record activity for at least 24 h at each of the following embryonic days: 6, 12, 15, and 18. Segment data into light and dark periods to detect stage‑specific patterns.

Minimize handling‑induced stress. Conduct all cage checks with gloved hands, limit exposure time to under 30 s, and allow a 24 h acclimation period after any manipulation before resuming recordings.

Process raw data with a consistent pipeline. Apply a low‑pass filter to remove high‑frequency noise, set a displacement threshold (e.g., 0.5 cm) to distinguish meaningful movement from tremor, and calculate bout duration and inter‑bout intervals. Use mixed‑effects models to account for litter and individual variability.

Validate the refined protocol through pilot experiments. Compare results across at least two independent laboratories, ensuring identical hardware and software settings. Publish full methodological details, including calibration files and analysis scripts, to facilitate reproducibility.

Key elements of the refined protocol:

Uniform environmental parameters (temperature, humidity, lighting)
Identical cage specifications and enrichment
Continuous infrared video recording with ≥ 1 s resolution
Automated tracking software with defined movement thresholds
Scheduled recordings at defined gestational days and circadian phases
Minimal, standardized handling procedures
Transparent data processing workflow and statistical analysis plan
Cross‑lab validation and comprehensive reporting

By adhering to these specifications, researchers obtain reliable quantifications of locomotor frequency in pregnant mice, enabling robust comparisons across studies and advancing understanding of gestational physiology.

Understanding Reproductive Health Indicators

Monitoring the locomotor activity of gestating rodents provides quantitative data that reflect maternal physiological status. Frequent movement patterns correlate with hormonal balance, cardiovascular function, and energy allocation, all of which influence fetal growth.

Key activity metrics include:

Total distance covered per observation period.
Number of movement bouts and average bout length.
Peak speed and acceleration during active phases.
Temporal distribution of activity relative to the light‑dark cycle.

These parameters serve as proxies for reproductive health. Elevated locomotion often indicates lower stress hormone concentrations and adequate nutrient availability, supporting normal placental development. Conversely, reduced activity may signal metabolic strain, compromised uterine blood flow, or early signs of gestational complications.

Accurate measurement requires continuous video tracking or infrared beam systems calibrated for pregnant subjects. Data should be normalized to body mass and gestational stage to avoid confounding effects of maternal weight gain. Statistical models that incorporate repeated measures across days can reveal trends and predict outcomes such as litter size, birth weight, and post‑natal survival.

Integrating movement frequency with additional biomarkers—e.g., plasma progesterone, glucose tolerance, and uterine artery Doppler indices—strengthens the assessment of reproductive health and enhances the predictive power of preclinical studies.