Normal Crown-Rump Length at 7 Weeks 5 Days
At 7 weeks and 5 days of gestation (53 days from last menstrual period), the normal crown-rump length is approximately 12-14 mm. 1, 2
Expected CRL Range at 7w5d
Based on large population studies using transvaginal ultrasound, the CRL at 53 days gestational age (7w5d) ranges from approximately 11.5-14 mm, with a mean around 12-13 mm 1, 2
The American College of Radiology defines CRL as the greatest linear dimension of the embryo measured from crown to rump, excluding limbs and yolk sac, and this measurement becomes visible on transvaginal ultrasound at approximately 6 weeks gestational age 3
At this gestational age, CRL measurements should be reported in millimeters (not centimeters) to ensure accuracy 3
Clinical Significance at This Gestational Age
Any embryo with CRL ≥7 mm must demonstrate cardiac activity; absence of cardiac activity at this size definitively confirms embryonic demise 4, 3
At 7w5d with an expected CRL of 12-14 mm, cardiac activity should be clearly visible by transvaginal ultrasound if the embryo is viable 4
The American College of Obstetricians and Gynecologists recommends that CRL measurement is the most accurate method for determining gestational age in the first trimester, with precision within ±5-7 days when measured between 8-13 weeks 3
Measurement Technique Considerations
CRL should be measured along the longest axis of the embryo using transvaginal ultrasound for optimal accuracy at this early gestational age 4, 3
The measurement represents the maximum straight-line distance from the top of the head to the bottom of the buttocks, excluding limbs and yolk sac 3
When there is a discrepancy between last menstrual period dating and CRL-based dating, the gestational age determined by CRL measurement should be adopted 3