Abstract
BackgroundUltrasonography is essential in the prenatal diagnosis and care for the pregnant mothers. However, the measurements obtained often contain a small percentage of unavoidable error that may have serious clinical implications if substantial. We therefore evaluated the level of intra and inter-observer error in measuring mean sac diameter (MSD) and crown-rump length (CRL) in women between 6 and 10 weeks’ gestation at Mulago hospital.MethodsThis was a cross-sectional study conducted from January to March 2016. We enrolled 56 women with an intrauterine single viable embryo. The women were scanned using a transvaginal (TVS) technique by two observers who were blinded of each other’s measurements. Each observer measured the CRL twice and the MSD once for each woman. Intra-class correlation coefficients (ICCs), 95% limits of agreement (LOA) and technical error of measurement (TEM) were used for analysis.ResultsIntra-observer ICCs for CRL measurements were 0.995 and 0.993 while inter-observer ICCs were 0.988 for CRL and 0.955 for MSD measurements. Intra-observer 95% LOA for CRL were ± 2.04 mm and ± 1.66 mm. Inter-observer LOA were ± 2.35 mm for CRL and ± 4.87 mm for MSD. The intra-observer relative TEM for CRL were 4.62% and 3.70% whereas inter-observer relative TEM were 5.88% and 5.93% for CRL and MSD respectively.ConclusionsIntra- and inter-observer error of CRL and MSD measurements among pregnant women at Mulago hospital were acceptable. This implies that at Mulago hospital, the error in pregnancy dating is within acceptable margins of ±3 days in first trimester, and the CRL and MSD cut offs of ≥7 mm and ≥ 25 mm respectively are fit for diagnosis of miscarriage on TVS. These findings should be extrapolated to the whole country with caution. Sonographers can achieve acceptable and comparable diagnostic accuracy levels of MSD and CLR measurements with proper training and adherence to practice guidelines.
Highlights
Ultrasonography is essential in the prenatal diagnosis and care for the pregnant mothers
This study found a strong observer agreement with intraand inter-observer intraclass correlation coefficient (ICC) ≥0.955 and this is similar to findings from other studies [29, 30]
Our study has shown that intra and inter-observer error of crown-rump length (CRL) and mean sac diameter (MSD) measurements among pregnant women in our setting were within acceptable limits
Summary
Ultrasonography is essential in the prenatal diagnosis and care for the pregnant mothers. In the early stages of a pregnancy, ultrasound is essential in predicting the risk of adverse pregnancy outcomes such as aneuploidy, stillbirth, Ali et al BMC Pregnancy and Childbirth (2018) 18:129 to be ±18.78% limits of agreement in United Kingdom (UK) [11] If significant, this error has implications on the accuracy of estimates of the fetal gestation age obtained. If not taken into account at MSD or CRL cut offs used for the diagnosis of miscarriage, some normal pregnancies may be erroneously deemed non-viable [11] This could lead to inadvertent termination of viable embryos and immense physical and emotional harm to the patient [11,12,13]. The use of the outdated CRL cut off of 5 mm increases the risk of misdiagnosing normal pregnancies This practice guidelines does not provide clear guidance for measurement of MSD [20].
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