Ultrasound Fetal Age Calculator

Estimate gestational stage and approximate parturition timing from fetal measurements.

Patient & scan

Species

Maternal weight

MeasurementInner Chorionic Cavity

Ultrasound measurement(s) mm

Fetus 1

Scan date

🐣 Estimated fetal age

Enter a valid measurement to estimate timing.

Ultrasound Reference

ICC — Inner Chorionic Cavity

Obtain the maximal transverse gestational-sac plane, measure the largest and smallest perpendicular internal diameters at 90° between the inner walls, average them, and enter the mean in mm.

Canine pregnancy ultrasound demonstrating inner chorionic cavity diameter measurement. — Inner chorionic cavity (ICC): measure two perpendicular inner diameters and use their mean.
Cropped from Vieira et al. (2020), Figure 1E. CC BY. DOI: 10.1590/1984-3143-AR2020-0037

BPD — Biparietal Diameter

Use a correctly aligned fetal head plane and measure the greatest external distance across the symmetrical parietal bones in a transverse view.

Canine fetal ultrasound demonstrating biparietal diameter measurement across the parietal bones. — Biparietal diameter (BPD): measure the greatest external distance between the parietal bones on a transverse view.
Cropped from Vieira et al. (2020), Figure 1A. CC BY. DOI: 10.1590/1984-3143-AR2020-0037

Dog developmental landmarks

~Day 19–21 sacs · ~Day 23–26 cardiac activity · ~Day 35–39 bladder/stomach · ~Day 48–54 intestinal layering.

Evidence & References

Luvoni & Grioni (2000), J Small Anim Pract.

Beccaglia & Luvoni (2006), J Small Anim Pract.

Beccaglia et al. (2016), Reprod Domest Anim. doi:10.1111/rda.12782

Alonge et al. (2016), J Small Anim Pract. doi:10.1111/jsap.12534

Górka et al. (2025), Theriogenology. doi:10.1016/j.theriogenology.2024.10.030

Vieira CA, Bittencourt RF, Biscarde CEA, et al. (2020). Estimated date of delivery in Chihuahua breed bitches, based on embryo-fetal biometry, assessed by ultrasonography. Animal Reproduction, 17(3), e20200037. doi:10.1590/1984-3143-AR2020-0037

Ultrasonographic fetometry provides an estimate of gestational stage and parturition timing. Accuracy varies with gestational stage, breed, litter characteristics, fetal positioning, measurement technique and operator experience. This tool supports veterinary judgement and does not replace clinical assessment.