In dogs, when can fetal heartbeat be detected by ultrasound, and when can fetal skeleton be visualized on radiographs?

• A. Heartbeat: day 10–14; Skeleton: day 60–65
• B. Heartbeat: day 22–28; Skeleton: day 42–45
• C. Heartbeat: day 40–50; Skeleton: day 80–85
• D. Heartbeat: day 60–65; Skeleton: day 90–95

Answer: (B)

In dogs, the sequence of fetal development shows heartbeat first, then bone mineralization. Fetal cardiac activity is detectable by ultrasound around about three to four weeks into gestation, commonly cited as roughly 22–28 days. The fetal skeleton becomes visible on radiographs later, once bones have begun to mineralize, which typically occurs around day 42–45 of gestation. Therefore, the best answer aligns with heartbeat detectable at 22–28 days and skeleton visible at 42–45 days. The other options place these events too early or too late compared with standard canine development. This timing helps in dating pregnancy and assessing viability with imaging.