Normal Ranges of Embryonic Length, Embryonic Heart Rate, Gestational Sac Diameter and Yolk Sac Diameter at 6–10 Weeks

Abstract

Objectives: To construct normal ranges for embryonic crown-rump length (CRL), heart rate (HR), gestational sac diameter (GSD) and yolk sac diameter (YSD) at 6–10 weeks of gestation. Methods: We examined 4,698 singleton pregnancies with ultrasound measurements of CRL, HR, GSD and YSD at 6–10 weeks and CRL at 11–13 weeks resulting in the live birth after 36 weeks of phenotypically normal neonates with birth weight above the 5th centile. Gestational age was derived from CRL at the 11- to 13-week scan using the formula of Robinson and Fleming. Regression analysis was used to establish normal ranges of CRL, fetal HR, GSD and YSD with gestation, and fetal HR, GSD and YSD with CRL. Results: At 6–10 weeks there were significant quadratic associations between CRL, GSD, YSD and gestation and between HR, GSD, YSD and CRL, and a cubic association between HR and gestation. The estimated gestation from CRL was the same as that of Robinson and Fleming for a CRL of 10.2–36.5 mm, but the formula of Robinson and Fleming underestimated the gestation by 1 day for a CRL 7.4–10.2 mm and this increased to 9 days for a CRL of 1 mm. Conclusion: This study established normal ranges for early pregnancy biometry.

Miscarriage and early first trimester growth restriction by ultrasound

“…Even in those with known LMP and regular cycles there is a discrepancy of more than 5 days in gestation calculated from the menstrual history and by ultrasound in about 25% of cases. 8 In one retrospective study, the predictive accuracy of CRL discordance for single foetal loss was high (AUC = 0.93; 95% CI = 0.91-0.94). A significant association was found between the increase in the degree of embryonic discordance and the likelihood of early fetal loss (P < 0.0001).…”

“…7,8,9 This is in part due to the fact, that, when using cross-sectional data to assess foetal size, gestational age assessment relies on accurate recall of the last menstrual period (LMP). 7 It is known, that, reporting of LMP is susceptible to bias, with a general tendency for women to overestimate their gestational age 5 and thus be found to have a discrepancy between observed and expected foetal size measurements.…”

Correlation analysis between ultrasound findings and abnormal karyotypes in the embryos from early pregnancy loss after in vitro fertilization-embryo transfer

“…The embryonic heart rate was measured from frozen M-mode images using electronic calipers [24]. The ultrasound parameters were compared with the biometric reference data presented in Papaioannou et al's [25] report, which provides reference values for embryonic pole length, embryonic heart rate, gestational sac diameter, and yolk sac diameter relative to gestational age (GA)/embryonic pole length in normal pregnancies. GAs were accurately recorded in this study, which was helpful for assessing the ultrasound findings.…”

“…Six different categories of ultrasound findings were identified from repeated TVS scans of 2172 embryos associated with EPL after IVF-ET: (1) normal ultrasound, 440 cases; the measurements of the gestational sac, yolk sac and embryonic pole were consistent with the GA of the embryo (all were between the fifth and 95th percentile for the expected size) [25]; (2) empty sac, 491 cases with an absence of fetal structures inside the gestational sac [18]; (3) yolk sac only, 454 cases; only a yolk sac was present in the gestational sac, and no embryonic pole or cardiac activity were present [4]; (4) small gestational sac, 86 cases; the diameter of the gestational sac was <5th percentile for its expected size, but the embryonic pole length >5th percentile for its expected size [25]; (5) small embryonic pole, 311 cases; the diameter of the gestational sac was consistent with or larger than predicted based on GA (≥5th percentile for the expected size), but the embryonic pole length was shorter than expected (<5th percentile for the expected size) [25]; and (6) early symmetrical arrested growth, 390 cases; simultaneous growth arrest of the gestational sac and the embryonic pole occurred (both <5th percentile for their expected size) [25].…”

A Critique of Early Childhood Development Research and Practice in Africa

“…The establishment of normal ranges in respect of physical attributes involves a similar statistical technique (Montgomery and Connolly 1987;Springer, Marin, Cyhan, Roberts and Gill 2007;Papaioannou et al 2010;Smits-Engelsman, Klerks and Kirby 2010;Sibley, Straus, Inness, Salbach and Jaglal 2013;Lindemann 2014). This statistical approach employed in physical sciences also leads to a situation where the normal ranges identified are as biased as those developed in psychological science.…”