Baby in ultrasound scan
An ultrasound of a human fetus measured to be 1.67 cm from crown to rump and estimated to have a gestational age of 8 weeks and 1 day. Image courtesy: Wikipedia

How is CRL measured in pregnancy scans?

how is crl measured in pregnancy scans

CRL measurement in pregnancy is estimated during the first trimester and is done between six and fourteen weeks approximately.

The baby’s height is measured from the top of its head to the bottom of the buttocks by excluding the limbs and yolk sac measurement.

Why is CRL measurement important in pregnancy?

1. To find out gestational age:

Gestational age is a common medical term used to indicate pregnancy age. In short, this is the length of time a fetus has been growing inside the mother’s uterus.

Your doctor will compare the CRL measurement to your last menstrual period (LMP) date to calculate your baby’s gestational age.

This data is more helpful in finding gestational age in case of irregular menstrual history.

2. Predictor of low birth weight:

CRL measurements also play a significant role in predicting the birth weight of the baby . Also, helps detect any potential complications in the fetus. Let’s say the CRL measurement of the fetus is smaller than the ideal measurement for that particular gestational age; it might be a sign of risk associated with fetal growth restriction or other developmental issues in the fetus.

3. Predictor of Missed Miscarriage:

A normal CRL measurement with a proper fetal heartbeat is a strong sign that your pregnancy is progressing in a positive way. Thus, CRL measurement plays a major role in ensuring the viability and safety of the baby.

What is the Normal CRL In Pregnancy?

what is normal crl in pregnancy
A normal CRL in pregnancy is the ideal length that is considered safe. The normal CRL value depends on the gestational age of the baby.
CRL Value
Approximate fetus CRL measurement at different stages of gestation

Factors that Affect the CRL Measurement

factors that affect crl measures in pregnancy

CRL Measurement in Multiple Pregnancy

crl measurement in multiple pregnancy

The CRLs between co-twins correspond with numerous pregnancies. However, there is a chance that variations will be seen in multifetal pregnancies.

After the second trimester, the estimation of the gestational age in multiple pregnancies is not advisable since the growth curves of singleton and multiple pregnancies vary.

Significance of MSD and CRL measurements

significance of msd and crl measurements

The Mean Sac Diameter (MSD) measures the gestational sac, which is usually seen around 3 weeks after conception in a scan. The MSD measurements are around 2 mm to 3mm when the gestational age is over 5 weeks.

The MSD measurement is as important as the CRL measurement in pregnancy. In a healthy pregnancy, the MSD should be at least 5 mm greater than the CRL of the baby.

CRL Facts


Each and every scan the doctor prescribes throughout the course of the pregnancy is very important to ensure the safety of the baby.

The soft markers can be shown at any stage of the pregnancy, not just the first trimester. Ensure that you do not miss any of the scans suggested by the fetal specialist.


1. What does small CRL mean?

The first-trimester pregnancy with a small gestation and a decreased CRL measurement has an increased likelihood of miscarriage.

2. What does large CRL mean?

Babies with LGA (larger than gestational age) are characterized by CRL measurements larger than expected at 11 to 14 weeks gestation.

3. What is CRL in a 7-week pregnancy?

The ideal CRL at 7 weeks of pregnancy is around 11mm.

4. What is CRL in 6 weeks of pregnancy?

The normal CRL value during the first 6 weeks of pregnancy is around 4mm.

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