Crown-rump length

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An ultrasound showing an embryo measured to have a crown-rump length of 1.67 cm and estimated to have a gestational age of 8 weeks and 1 day Ultrasound of human fetus, 8 weeks and 1 day.jpg
An ultrasound showing an embryo measured to have a crown-rump length of 1.67 cm and estimated to have a gestational age of 8 weeks and 1 day

Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump). It is typically determined from ultrasound imagery and can be used to estimate gestational age.

Contents

Introduction

Diagram showing crown-rump length by gestational age. The blue line is the mean and the green area delimits the 3rd versus the 97th percentile. Crown-rump length by gestational age.png
Diagram showing crown-rump length by gestational age. The blue line is the mean and the green area delimits the 3rd versus the 97th percentile.
Ultrasound image of the foetus at 12 weeks of pregnancy in a sagittal scan. Measurements of fetal Crown Rump Length (CRL). CRL Crown rump length 12 weeks ecografia Dr. Wolfgang Moroder.jpg
Ultrasound image of the foetus at 12 weeks of pregnancy in a sagittal scan. Measurements of fetal Crown Rump Length (CRL).

The embryo and fetus float in the amniotic fluid inside the uterus of the mother usually in a curved posture resembling the letter C. The measurement can actually vary slightly if the fetus is temporarily stretching (straightening) its body. The measurement needs to be in the natural state with an unstretched body which is actually C shaped. The measurement of CRL is useful in determining the gestational age (menstrual age starting from the first day of the last menstrual period) and thus the expected date of delivery (EDD). Different human fetuses grow at different rates and thus the gestational age is an approximation. Recent evidence has indicated that CRL growth (and thus the approximation of gestational age) may be influenced by maternal factors such as age, smoking, and folic acid intake. Early in pregnancy gestational age 8 weeks, it is accurate within about +/- 5 days but later in pregnancy due to different growth rates, the accuracy is less. In that situation, other parameters can be used in addition to CRL. The length of the umbilical cord is approximately equal to the CRL throughout pregnancy.

Gestational age is not the same as fertilization age. It takes about 14 days from the first day of the last menstrual period for conception to take place and thus for the conceptus to form. The age from this point in time (conception) is called the fertilization age and is thus 2 weeks shorter than the gestational age. Thus a 6-week gestational age would be a 4-week fertilization age. Some authorities however casually interchange these terms [ citation needed ] and the reader is advised to be cautious. An average gestational period (duration of pregnancy from the first day of the last menstrual period up to delivery) is 280 days. On average, this is 9 months and 6 days.

Gestational age estimation

A commonly used estimate of gestational age in weeks is (as described by Verburg et al. [2] ):

Crown–rump length (CRL) in relation to gestational age [2]
CRL (mm)Gestational age (weeks + days)
5th centileMedian95th centile
55 + 66 + 26 + 6
107 + 07 + 48 + 1
157 + 58 + 29 + 0
208 + 29 + 09 + 5
258 + 69 + 410 + 2
309 + 210 + 010 + 6
359 + 510 + 311 + 2
4010 + 110 + 611 + 5
4510 + 311 + 212 + 1
5010 + 611 + 512 + 4
5511 + 112 + 013 + 0
6011 + 312 + 313 + 3
6511 + 612 + 513 + 5
7012 + 113 + 014 + 0
7512 + 313 + 314 + 3
8012 + 513 + 514 + 5
8513 + 014 + 015 + 1
9013 + 214 + 215 + 3
9513 + 414 + 415 + 5
10013 + 615 + 016 + 1

Gestational age estimation in days is carried out according to the equations:

 ; and SD of GA = 2.39102 + (0.0193474 × CRL).

See also

Related Research Articles

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The estimated date of delivery (EDD), also known as expected date of confinement, and estimated due date or simply due date, is a term describing the estimated delivery date for a pregnant person. Normal pregnancies last between 38 and 42 weeks. Children are delivered on their expected due date about 4% of the time.

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<span class="mw-page-title-main">Prenatal nutrition</span>

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Anthropometry is defined as the scientific study of the human body measurements and proportions. These studies are generally used by clinicians and pathologists for adequate assessments of the growth and development of the fetus at any specific point of gestational maturity. Fetal height, fetal weight, head circumference (HC), crown to rump length (CR), dermatological observations like skin thickness etc. are measured individually to assess the growth and development of the organs and the fetus as a whole and can be a parameter for normal or abnormal development also including adaptation of the fetus to its newer environment.

References

  1. Ohuma EO, Papageorghiou AT, Villar J, Altman DG (December 2013). "Estimation of gestational age in early pregnancy from crown-rump length when gestational age range is truncated: the case study of the INTERGROWTH-21st Project". BMC Medical Research Methodology. 13: 151. doi:10.1186/1471-2288-13-151. PMC   4029763 . PMID   24314232.
    Crown rump length before a gestational age of 9 weeks is extrapolated by assuming a crown rump length of 0 at a gestational age of 2 weeks, corresponding to an embryonic age of 0 weeks. This extrapolated part is blurred because of uncertain values.
  2. 1 2 Verburg BO, Steegers EA, De Ridder M, Snijders RJ, Smith E, Hofman A, et al. (April 2008). "New charts for ultrasound dating of pregnancy and assessment of fetal growth: longitudinal data from a population-based cohort study". Ultrasound in Obstetrics & Gynecology. 31 (4): 388–96. doi: 10.1002/uog.5225 . PMID   18348183. S2CID   349860.