Ultrasound Review: Fetal Size, Pregnancy Dating and CRL Measurement

This literature review examines the use of ultrasound in determining fetal size and pregnancy dating, focusing on crown-rump length (CRL) measurements. It analyzes two key articles: one detailing the INTERGROWTH-21st Project's development of international standards for early fetal size and CRL measurement, and another evaluating the methodological quality of studies reporting gestational age estimation via CRL. The review highlights the importance of standardized protocols, quality control, and representative sampling in ultrasound research. It also emphasizes the heterogeneity in existing studies and the need for innovative methodological designs to improve the reliability and universal applicability of gestational age estimation methods. Desklib provides access to this and other solved assignments for students.

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Ultrasound
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Article 1:
Papageorghiou, A. T., et al. "International standards for early fetal size and pregnancy dating
based on ultrasound measurement of crown–rump length in the first trimester of
pregnancy." Ultrasound in Obstetrics & Gynecology 44.6 (2014): 641-648.
Assessment of gestational age (GA) during pregnancy is necessary to effectively observe
fetal growth patterns, anatomy and predict the date of delivery of the newborn. The GA
calculation for fetus is mostly done by ultrasound measurement of fetal crown-rump length
(CRL) at or above 14 weeks of gestation1. One research study focused on developing the first
international standards for early fetal size and CRL measurement by optimizing study design and
using prescriptive approach in the procedure. Research in this area was necessary due to
methodological limitations found in past approach used for CRL measurement. The project was
named as the INTERGROWTH-21ST Project and population based recruitment method selected
women with singleton pregnancy between 9 + 0 and 13 + 6 weeks of gestation. The GA for the
participants was calculated by means of last menstrual period and lack of hormonal medication
in the past 2 months. Secondly, CRL was measures under strict protocols such as strict training
and standardization for CRL measurement. The follow up with the participants until delivery and
hospital discharge gave idea about GA estimation by means of CRL data. The result showed
uniform increase in CRL with GA2.
1 Holman, Michelle A., et al. "444: Effect of fresh versus frozen embryo transfer on fetal growth
parameters." American Journal of Obstetrics & Gynecology 218.1 (2018): S268-S269.
2 Papageorghiou, A. T., et al. "International standards for early fetal size and pregnancy dating based on ultrasound
measurement of crown–rump length in the first trimester of pregnancy." Ultrasound in Obstetrics &
Gynecology 44.6 (2014): 641-648.

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The strength of the study is its sample as it selected participants from eight
geographically diverse countries, thus making the outcome generalizable for all population
group. This increases the chance for the project to become a universal project for GA
measurement. Secondly, another reason for the success of the project was that the researcher paid
strict emphasis on quality control process and keeping unified protocols in all phase starting from
recruitment to hospital discharge. This approach favored creating international standard for
measuring fetal growth. The outcome of the INTERGROWTH-21ST Project has also been
evaluated by another study which showed that reliable estimates can be obtained from the
project3.
Article 2:
Napolitano, R., et al. "Pregnancy dating by fetal crown–rump length: a systematic review of
charts." BJOG: An International Journal of Obstetrics & Gynaecology 121.5 (2014): 556-565.
Another study focused on evaluating the methodological quality of studies reporting
about GA estimation by CRL and the systematic review of observational studies was done using
the MOOSE (Meta-analyses of Observation studies in Epidemiology) group checklist. The
articles published between 1948- 20111 were retrieved from three electronic databases namely
MEDLINE, EMBASE and CINAHL. The criteria for selecting article were that it should report
about GA estimation from first trimester CRL measurement using ultrasound. About 1142
relevant citations were found and four of them had lowest risk of boas. Based on 29 set criteria,
the articles were scores as having low or high risk of bias. Some studies used cross sectional
3 Ohuma, Eric O., et al. "Estimation of gestational age in early pregnancy from crown-rump length when gestational
age range is truncated: the case study of the INTERGROWTH-21 st Project." BMC medical research
methodology 13.1 (2013): 151.

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research design and some used longitudinal research design. Five articles used mix of both
methods. The result varies across setting and several limitations such as lack of description about
population were found. The ultrasound aspects was well-described in most of the research
articles, however there were also studies that failed to provide the equation for GA and CRL4.
The conclusion from the evaluation of above article is that great heterogeneity has been
found in studies regarding use of CRL for GA estimation. The most significant limitation was the
approach taken to selected samples for the study. Consideration of the sample was important to
effectively create reference equations for sample size. Secondly, in some studies, women with
low risk of complication were not taken. However, this should be considered because certain
conditions like hypertension, smoking and any disease can affect early fetal growth in the first
trimester of pregnancy5. Hence, there is a need for innovative methodological design to reduce
the variability in results obtained for GA estimation. Future studies need to focus in developing a
design that can be universally accepted for GA estimation.
4 Napolitano, R., et al. "Pregnancy dating by fetal crown–rump length: a systematic review of charts." BJOG: An
International Journal of Obstetrics & Gynaecology 121.5 (2014): 556-565.
5 Bouwland-Both, Marieke I., et al. "Prenatal parental tobacco smoking, gene specific DNA methylation, and
newborns size: the Generation R study." Clinical epigenetics 7.1 (2015): 83.

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References:
Bouwland-Both, Marieke I., et al. "Prenatal parental tobacco smoking, gene specific DNA
methylation, and newborns size: the Generation R study." Clinical epigenetics 7.1 (2015): 83.
Holman, Michelle A., et al. "444: Effect of fresh versus frozen embryo transfer on fetal growth
parameters." American Journal of Obstetrics & Gynecology 218.1 (2018): S268-S269.
Napolitano, R., et al. "Pregnancy dating by fetal crown–rump length: a systematic review of
charts." BJOG: An International Journal of Obstetrics & Gynaecology 121.5 (2014): 556-565.
Ohuma, Eric O., et al. "Estimation of gestational age in early pregnancy from crown-rump length
when gestational age range is truncated: the case study of the INTERGROWTH-21 st
Project." BMC medical research methodology 13.1 (2013): 151.
Papageorghiou, A. T., et al. "International standards for early fetal size and pregnancy dating
based on ultrasound measurement of crown–rump length in the first trimester of
pregnancy." Ultrasound in Obstetrics & Gynecology 44.6 (2014): 641-648.