- Fetal volume and crown-rump length from 7 to 10 weeks of gestational age in singletons and twins. Martins WP, Nastri CO, Barra DA, Navarro PA, Mauad Filho F, Ferriani RA. Eur J Obstet Gynecol Reprod Biol. 2009 Jul;145(1):32-5. Epub 2009 Apr 21. PMID: 19386409
- "Twins and singletons had similar fetal volume and crown-rump length between the 7th and 10th week of gestational age. Additionally, fetal volume assessed by VOCAL was better than crown-rump length to estimate the gestational age at the evaluated period. However, the improvement was small and probably without clinical significance. CONDENSATION: Fetal volume and crown-rump length were similar between singletons and twins. Fetal volume relative increase was higher and the predicted gestational age was better."
- Fetal crown-rump length and estimation of gestational age in an ethnic Chinese population. Sahota DS, Leung TY, Leung TN, Chan OK, Lau TK. Ultrasound Obstet Gynecol. 2009 Feb;33(2):157-60. PMID: 19115262
- "The best-fit equation for the sonographic estimate of gestational age (GA, in days) from CRL (in mm) was GA = 26.643 + 7.822 x CRL(1/2)(R(2) = 0.96). The mean difference between menstrual age and the predicted gestational age was 0.22 days (95% CI, - 0.14 to 0.56), which was lower than that of the three established CRL dating formulae. CONCLUSION: We have derived a formula suitable for the dating of naturally conceived pregnancies between 6 and 15 weeks of gestation that has no systematic prediction error (the 95% CI of mean difference between predicted and menstrual age included zero), comparing favorably with established CRL dating formulae."