Dating ultrasound measurements
It should be possible to generate very accurate reference charts by using a large in vitro fertilisation (IVF) cohort where CRL measurements could be correlated with gestational age precisely calculated from date of fertilisation.
Accuracy could be further enhanced by using measurements obtained from high-resolution transvaginal scans by sonologists specialising in Women’s Health.
Accurate determination of gestational age underpins good obstetric care.
We assessed the performance of six existing ultrasound reference charts to determine gestational age in 1268 singleton IVF pregnancies, where “true” gestational age could be precisely calculated from date of fertilisation.
OBJECTIVES There are no international standards for relating fetal crown-rump length (CRL) to gestational age (GA), and most existing charts have considerable methodological limitations.
The INTERGROWTH-21(st) Project aimed to produce the first international standards for early fetal size and ultrasound dating of pregnancy based on CRL measurement.
Ethics approval was obtained before we commenced the study (Project 05063, Monash Surgical Private Human Research Ethics Committee, Clayton, VIC, Australia).
For this retrospective database study where we used de-identified data in aggregate, the ethics committee specifically approved our request not to obtain individual patient consent.
All ultrasounds were transvaginal, done on Advanced Technology Laboratories HDI 5000 ultrasound machines by experienced sonographers.
These were identified from a total cohort of 4971 first trimester ultrasound reports of IVF and naturally conceived pregnancy scans.
Pregnancies that resulted from frozen embryos transfer, complicated by fetal structural anomalies, delivered before 24 weeks, or had missing data were all excluded.
Accurate dating of gestational age is central to good obstetric care.
It allows the clinicians to better time gestation-specific antenatal screening tests, reduces erroneous labelling of pregnancies as very preterm, preterm, and small-for-gestational-age, and decreases the risk of inappropriate induction of labour [1–5].