Gestational age
Last revised by Jeremy Jones ◉ on 20 Sep 2021
Citation, DOI, disclosures and article data
Citation:
Knipe H, Jones J, Lorenzzoni P, et al. Gestational age. Reference article, Radiopaedia.org (Accessed on 28 Sep 2023) https://doi.org/10.53347/rID-63195
Permalink:
rID:
63195
Article created:
Disclosures:
At the time the article was created Henry Knipe had no recorded disclosures.
View Henry Knipe's current disclosuresLast revised:
20 Sep 2021, Jeremy Jones ◉
Disclosures:
At the time the article was last revised Jeremy Jones had no recorded disclosures.
View Jeremy Jones's current disclosuresRevisions:
8 times, by 4 contributors - see full revision history and disclosures
Systems:
Synonyms:
- Gestational age (GA)
The gestational age (GA) of an embryo/fetus is most accurately determined by measuring the crown rump length (CRL) in the first trimester. The later the pregnancy, the larger the standard deviation of the estimated gestational age and thus estimated date of delivery (EDD) is. Mean sac diameter (MSD) before a fetal pole is identified and biparietal diameter (BPD) after 11 weeks can also be used to support the calculation of the gestational age.
The estimated date of delivery (EDD) should be calculated by last menstrual period (LMP) unless 1:
- unknown LMP
- GA by CRL is <10 weeks and differs from GA by LMP by >5 days
- GA by CRL (+/- BPD) is 10-14 weeks and differs from GA by LMP by >7 days
On this page:
Practical points
- for twin pregnancies, gestational age is based on the largest twin's CRL 1
Related pathology
See also
- automatic online gestational age calculator based on crown-rump length from www.perinatology.com
References
- 1. Mizia K, Campbell Westerway S, Robertson M et al. Guidelines for the Performance of the First Trimester Ultrasound. Australasian Journal of Ultrasound in Medicine. 2018;21(3):179-82. doi:10.1002/ajum.12102
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first trimester
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- embryo/fetus
- beta-hCG levels
- confirming intrauterine gestation
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- first trimester vaginal bleeding
- early structural scan
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second trimester
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