Complications & Concerns Crown Rump Length (CRL) on Ultrasounds By Krissi Danielsson Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage. Learn about our editorial process Krissi Danielsson Medically reviewed by Medically reviewed by Brian Levine, MD, MS, FACOG on September 24, 2019 Brian Levine, MD, MS, is board-certified in obstetrics and gynecology as well as in reproductive endocrinology and infertility. Learn about our Review Board Brian Levine, MD, MS, FACOG Updated on February 02, 2020 Print Chad Ehlers / Getty Images Crown-rump length (CRL) is an ultrasound measurement that is used during pregnancy. The baby is measured, in centimeters, from the top of their head (crown) to the bottom of their buttocks (rump). The limbs and yolk sac are not included in the measurement. The CRL can be measured starting around six or seven weeks of pregnancy up until 14 weeks. What Is Crown-Rump Length? CRL may be useful in calculating gestational age. With this gestational age, doctors can estimate your potential due date. The earlier the first ultrasound is performed, the more accurate the baby's gestational age will be. Once the fetus has developed past 14 weeks, head circumference, biparietal diameter, and femur length measurements are used to determine how the baby is progressing. The length of the umbilical cord is typically the same as the CRL throughout pregnancy. Reasons to Stay Calm When Short Femur Length Is Found Uses Once the fetus's CRL surpasses 7 mm, a heartbeat should be detected by transvaginal ultrasound –– an ultrasound that is performed through the vagina and not on top of the abdomen like a standard ultrasound. If no heartbeat or cardiac activity is detected, then the pregnancy is likely a missed miscarriage. A missed, or silent, miscarriage typically occurs without the normal miscarriage symptoms. The placenta may continue to supply hormones, which can mask the outward signs of a miscarriage. Women with a mean sac diameter (MSD) of less than 5 mm greater than the CRL are more likely to experience a first-trimester miscarriage –– even if the baby has a normal heart rate. Decreased crown-rump length can also diagnose chromosomal anomalies like trisomy 18 (Edwards syndrome) and other trisomies associated with growth restriction. Was this page helpful? Thanks for your feedback! Get diet and wellness tips to help your kids stay healthy and happy. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Ioannou C, Sarris I, Hoch L, Salomon LJ, Papageorghiou AT. Standardisation of crown-rump length measurement. BJOG. 2013;120 Suppl 2:38-41. doi:10.1111/1471-0528.12056 Broere-Brown ZA, Baan E, Schalekamp-timmermans S, Verburg BO, Jaddoe VW, Steegers EA. Sex-specific differences in fetal and infant growth patterns: a prospective population-based cohort study. Biol Sex Differ. 2016;7:65. doi:10.1186/s13293-016-0119-1 Bree RL, Edwards M, Böhm-vélez M, Beyler S, Roberts J, Mendelson EB. Transvaginal sonography in the evaluation of normal early pregnancy: correlation with HCG level. AJR Am J Roentgenol. 1989;153(1):75-9. doi:10.2214/ajr.153.1.75 Kapfhamer JD, Palaniappan S, Summers K, et al. Difference between mean gestational sac diameter and crown-rump length as a marker of first-trimester pregnancy loss after in vitro fertilization. Fertil Steril. 2018;109(1):130-136. doi:10.1016/j.fertnstert.2017.09.031