Estimation of the gestational age with LMP or with CRL

Postgraduate Thesis uoadl:2775174 369 Read counter

Unit:
Κατεύθυνση Παθολογία της Κύησης
Library of the School of Health Sciences
Deposit date:
2018-06-20
Year:
2018
Author:
Maroudias Georgios
Supervisors info:
Παπαντωνίου Νικόλαος, Καθηγητής, Ιατρική, ΕΚΠΑ
Χρέλιας Χαράλαμπος, Αναπληρωτής Καθηγητής, Ιατρική, ΕΚΠΑ
Συριστατίδης Χαράλαμπος, Αναπληρωτής Καθηγητής, Ιατρική, ΕΚΠΑ
Original Title:
Προσδιορισμός της ηλικίας κυήσεως με βάση την ΤΕΡ και το CRL
Languages:
Greek
Translated title:
Estimation of the gestational age with LMP or with CRL
Summary:
Introduction: A dating of pregnancy is important, as up to 30% of women attending an antenatal clinic have uncertain or unreliable menstrual dates. Antenatal care and interventions aimed at improving pregnancy outcome rely on our knowledge of the gestational age (GA). The potential benefits of correct ultrasound dating in the first trimester include : the improved performance of first trimester screening for chromosomal abnormalities, reducing the number of pregnancies classified as preterm and the reduced incidence of post term delivery. It has also been shown that dating the pregnancy in the first rather than the second trimester can lead to a reduction in the number of unnecessary inductions of labor. The unknown or unreliable gestational age has been linked with higher rates of perinatal mortality and morbidity. The exact dating of the pregnancy has even higher importance in the case of a twin pregnancy due to the increase incidence of adverse perinatal outcomes such as preterm delivery or fetal growth restriction.
Material-Methods: Eight electronic databases (PUBMED, WebMD, Wikipedia, ΕΜΒΑSE, American Society of Obstetrics-Gynecology, MedLine, Royal College of Obstetricians and Gynaecologists, British Medical Ultrasound Society) were systematically searched. We used the following keywords: last menstrual period, crown rump length, gestational age, estimated due date and first trimester ultrasound scan. Only articles written in English and Greek were considered. Our review resulted in 56 references (55 in English and 1 in Greek).
Results: According to the ACOG up to and including 13 6/7 weeks of gestation, gestational age assessment based on the on measurement of the crown rump length has an accuracy of +/- 5-7 days. Beyond measurements of 84mm (corresponding to approximately 14 0/7 weeks of gestation), the accuracy of the CRL to estimate gestational age decreases, and in these cases, other second trimester biometric parameters should be used for dating. If ultrasound dating before 14 0/7 weeks of gestation differs by more than 7 days from LMP dating, the EDD should be changed to correspond with the ultrasound dating. According to the RCOG all pregnancies should be dated based on the measurement of CRL during the first trimester ultrasound scan and not based to the LMP. A recent meta analysis (Napolitano 2013) evaluated the methodological quality used in studies reporting CRL equations to estimated GA using a set of predefined criteria. The 4 studies with the highest scores (lowest risk of bias) satisfied 18 or more of the 29 criteria, these showed lower variation in GA estimation than the remaining lower scoring studies. This was more evident at the extremes of GA. The INTERGROWTH-21st is a multicenter, multiethnic, population based project conducted between 2009 and 2014 in eight urban areas in eight different countries. It’s the first study aiming to generate CRL data according to GA using an optimal design and prescriptive approach in order to develop international ,population based standards for early fetal linear size estimation and ultrasound dating in the first trimester that can be used throughout the world.
Conclusions: A disadvantage of GA estimation based purely on the ultrasound measurement of fetal anatomical parameters is that all biological variation in the GA for a given value of CRL disappears, an assumption that is of course biologically implausible. That also occurs with any other biological parameter being predicted by a single measurement. When a reliable LMP and ultrasound estimate concur, small discrepancies in GA may mask inherent CRL measurement error. Conversely , an apparently reliable and accurate LMP with a substantial difference in estimated GA based on CRL should be considered as an indicator of possible growth disturbance or underlying pathology that needs to be monitored. It is important to emphasize that all estimates of GA should be explained and given to the corresponding measure of variability e.g. SD or centiles, to provide a measure of the error of the estimation. Finally when high methodological standards are met and populations adequately selected, early fetal growth is similar across populations. The adoption of these standards will standardize the evaluation of fetal growth across levels of care and facilitate comparisons internationally.
Main subject category:
Health Sciences
Keywords:
Gestational age, LMP, CRL
Index:
No
Number of index pages:
0
Contains images:
Yes
Number of references:
69
Number of pages:
96
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