What are the five most common fetal measurements used to determine fetal development?
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The AC can be measured and calculated with similar instruments used to measure the transverse HC. The calipers should be placed along the external perimeter of the fetal abdomen to include subcutaneous soft tissue. The following formula can be used to calculate the AC: Show
AC=(D1+D2×π)2 Therefore AC=(D1+D2)×1.57 In this equation, D1 is the diameter from the skin line behind the fetal spine to the outer skin line of the anterior abdominal wall, and D2 is the transverse diameter perpendicular to D1. Unlike in the fetal head (HC), there is no consistent relationship between the anteroposterior and transverse diameters of the AC. Sonographers must be sure to measure the AC at the skin line and not to the more obvious rib, spine, and peritoneal echoes. Of the four basic gestational age measurements, AC has the largest reported variability and is more affected by growth disturbances than the other basic parameters. Later in gestation, the AC correlates more closely with fetal weight than with age. View chapter on ClinicalKey NUTRITIONAL ASSESSMENT | Anthropometry and Clinical ExaminationJ.R. Lustig, B.J.G. Strauss, in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003 Abdominal:Gluteal Circumference RatioThe ratio of the abdominal circumference to the maximal gluteal circumference defines the distribution of adipose tissue in the body. The waist is measured with the subject standing erect and undressed. The abdominal circumference is measured at the midpoint of the line between the rib or costal margin and the iliac crest in the midaxillary line. The maximal gluteal (buttock) circumference is also measured with the subject standing erect. It is important to define the sites measured and maintain consistency in these sites in order to compare sets of data. A waist/hip ratio > 0.95 in males and > 0.85 females is consistent with abdominal obesity. Abdominal fat distribution is associated with a range of adverse health consequences, including an increased risk of cardiovascular and cerebrovascular disease, impaired glucose tolerance, and hypertriglyceridemia, even when the BMI is in the ‘healthy’ range. View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B012227055X008439 Fetal growth assessment by sonographySandra L. Hagen-Ansert MS, RDMS, RDCS, FASE, FSDMS, in Textbook of Diagnostic Sonography, 2018 Head circumference to abdominal circumference ratioThe HC to AC ratio was first developed to detect IUGR in cases of uteroplacental insufficiency. The HC to AC ratio is especially useful in differentiating symmetric and asymmetric IUGR. For each gestational age, a ratio is assigned with standard deviations. In an appropriate-for-gestational-age (AGA) pregnancy, the ratio should decrease as the gestational age increases. In the presence of IUGR and with the loss of subcutaneous tissue and fat, the ratio increases. This is counterintuitive because as the fetal AC decreases, the HC:AC ratio increases, and vice versa. The HC to AC ratio is at least 2 standard deviations above the mean in approximately 70% of fetuses affected with asymmetric IUGR. The HC to AC ratio is not very useful, however, in predicting symmetric IUGR, because the fetal head and fetal abdomen are both equally small. This can be further complicated in cases of fetal infections (TORCH infections), which can produce organomegaly with enlargement of the liver or spleen and the resulting increase in the abdominal circumference in the presence of fetal IUGR. View chapter on ClinicalKey A Diet with Carbohydrates Eaten Primarily at Dinner: An Innovative, Nutritional Approach to End the Vicious Cycle of Abdominal Obesity Fetal biometry measures your baby's size. During an ultrasound, your doctor measures the baby's head, body, and thigh bone. It helps show your baby's development.How the Test Is DoneFetal biometry is a measurement taken during a standard ultrasound. During the ultrasound, a technician puts a gel on your belly, and then gently moves the ultrasound wand on your stomach to see images of your baby. What to Know About Test ResultsYour doctor will use the fetal biometry to estimate your baby's age, size, weight, and growth. You may get a report after your scan with the measurements. The report may include:
If your baby's results are unusual, your doctor will suggest further testing. Small size may be a sign of intrauterine growth restriction (IUGR.) Large size may be a sign that the mother has a health problem, such as gestational diabetes. How Often the Test Is Done During Your PregnancyYour doctor will estimate the size of your baby during standard ultrasounds. Most women get one to three ultrasounds when they're pregnant. If you're at high risk, or if you're having twins, you may need ultrasounds more often. What are fetal measurements?Fetal ultrasound measurements can include the crown-rump length (CRL), biparietal diameter (BPD), femur length (FL), head circumference (HC), occipitofrontal diameter (OFD), abdominal circumference (AC), and humerus length (HL), as well as calculation of the estimated fetal weight (EFW).
How are fetal measurements most commonly taken?Fetal biometry, with the help of ultrasonography (USG) provides the most reliable and important information about fetal growth and well-being. Frequently used parameters for fetal measurements by this method are the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL).
How is fetal development measured?The measurement is generally defined as the distance in centimeters from the pubic bone to the top of the uterus. The expectation is that after week 24 of pregnancy the fundal height for a normally growing baby will match the number of weeks of pregnancy — plus or minus 2 centimeters.
What fetal measurements are needed to determine gestational age?In the second and third trimesters, fetal head, body, and extremity measurements have been commonly used to assess gestational age. Those parameters most commonly measured include biparietal diameter,20,21,22,23,24,25,26,27,28 head circumference,29,30 abdominal circumference,31,32,33,34,35 and femur length.
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