Complications & Concerns Significance of Femur Length in Pregnancy By Krissi Danielsson 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 Updated on June 14, 2021 Medically reviewed Verywell Family articles are reviewed by board-certified physicians and family healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Rachel Gurevich, RN Medically reviewed by Rachel Gurevich, RN Facebook LinkedIn Twitter Rachel Gurevich is a fertility advocate, author, and recipient of The Hope Award for Achievement, from Resolve: The National Infertility Association. She is a professional member of the Association of Health Care Journalists and has been writing about women’s health since 2001. Rachel uses her own experiences with infertility to write compassionate, practical, and supportive articles. Learn about our Medical Review Board Print Adene Sanchez / Getty Images Early in pregnancy, certain ultrasound findings such as the presence of a yolk sac and the crown-to-rump ratio are used to help determine the health of a pregnancy, the gestational age, and the possibility for pregnancy loss. After the first trimester, the embryo has developed into a fetus and new markers are used to narrow in on gestational age and assess the health of the baby. Loading shell for quizzesApp1 vue props component in Globe. Femur Length Measurement Among the markers used for assessing fetal growth and health is the length of the baby's femur, the long bone in the thigh. Measured from the blunt end of the bone to the shaft, the femur length is generally measured in millimeters. A short femur length finding on ultrasound may indicate the need for further testing to rule out certain conditions. But this measurement has many limitations, from human error to outdated ultrasound equipment to normal variation. Femur length is only one variable among many that should be used to make determinations about a baby's health. It is important to know that in the majority of these pregnancies (73%), parents will go on to have a full-term delivery of a healthy baby whose size is appropriate for gestational age. Possible Concerns With Short Femur Length When femur length is below the fifth percentile, parents may be advised about a number of potential atypical pregnancy outcomes. A short femur length identified on ultrasound in the second or third trimester raises concern for certain conditions in the fetus or the pregnancy. Dwarfism Fetuses with shorter-than-expected femur length have been found to be at higher risk for skeletal dysplasia, otherwise known as dwarfism. This is different from short stature, which is a height that is three or more standard deviations below the mean for age but is proportional. There are more than 200 disorders that can be categorized as skeletal dysplasia. All are characterized by a disproportionate skeleton due to cartilage and bone growth abnormalities. Placental Insufficiency Some studies have raised concerns about the sufficiency of the placenta to provide an adequate nutritional environment for fetuses with short femur lengths. Because of that, short femur length is linked to adverse pregnancy outcomes such as fetuses that are small for gestational age, babies born with low birth weight, and preterm birth. Aneuploidies A femur length that is shorter than expected can also be a soft marker for certain genetic conditions, such as trisomy 21 (Down syndrome), trisomy 13 (Patau syndrome), and trisomy 18 (Edward's syndrome). Soft markers are indicators found on ultrasounds that are not abnormalities on their own, but characteristics that occur more often in fetuses with chromosomal trisomies. Compared to high-level markers such as nuchal skin fold, femur length is considered a low-level marker for Down syndrome. The presence of any of these markers may simply indicate a need for more prenatal testing. Genetic Counseling in Pregnancy A Word From Verywell It can be frightening to hear that your baby has a short femur length, or another marker of concern. However, in most cases, the outcome is still a healthy, full-term baby. If your doctor finds that your baby has a shorter than expected femur length, further testing may help you and your healthcare provider understand what this measurement means and how best to care for your baby during pregnancy, at birth, and beyond. 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 5 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. Smith M, Nicoll A. Perinatal outcomes following mid trimester detection of isolated short foetal femur length. J Obstet Gynaecol. 2018;38(5):727. doi:10.1080/01443615.2018.1444408 Mailath-Pokorny M, Polterauer S, Worda K, Springer S, Bettelheim D. Isolated short fetal femur length in the second trimester and the association with adverse perinatal outcome: Experiences from a tertiary referral center. PLoS ONE. 2015;10(6):e0128820. doi:10.1371/journal.pone.0128820 Bonafe L, Cormier-Daire V, Hall C, et al. Nosology and classification of genetic skeletal disorders: 2015 revision. Am J Med Gen Part A. 2015;167A(12):2869-92. doi:10.1002/ajmg.a.37365 D'Ambrosio V, Vena F, Marchetti C, et al. Midtrimester isolated short femur and perinatal outcomes: A systematic review and meta-analysis. Acta Obstet Gynecol Scand. 2019;98(1):11-17. doi:10.1111/aogs.13470 Mathiesen, JM, Aksglaede, L, Skibsted, L, Petersen, OB, Tabor, A. Outcome of fetuses with short femur length detected at second-trimester anomaly scan: A national survey. Ultrasound Obstet Gynecol. 2014;44(2):160-5. doi:10.1002/uog.13286