Estimated Fetal Weight Percentile Chart
Fetal Growth Percentile Charts:Measurement Charts:BPD - OFD - HC | Femur and Humerus (FL HL) | Abdominal Circumference (AC) BIPARIETAL DIAMETER AND HEAD CIRCUMFERENCE | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The
BPD and OFD are measured on a transverse axial section of the fetal
head which includes the falx cerebri anteriorly and posteriorly, the
cavum septum pellucidum anteriorly in the midline and the thalami. The
BPD is measured from the outer edge of the nearer parietal bone to the
inner edge of the more distant parietal bone. The OFD is measured
perpendicular to the BPD.  FEMUR AND HUMERUS LENGTH  ABDOMINAL CIRCUMFERENCEThe abdominal circumference is measured at the level of the liver and stomach, including the left portal vein at the umbilical region.  | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ultrasonic Fetal Measurement Standards | ||
If
we assume a fetus is growing normally, biometric measurements are
determined by gestational age, and we can estimate the gestational age
and thus the due date. When the date of the last menses preceding
conception is known, it is usually a more accurate estimate (+/- 5 days)
of EDCWhen using ultrasound to estimate gestational age, remember
that we are assuming the fetus is growing normally. Conditions which
alter fetal growth will make the estimates less reliable. Although many
embryonic and fetal structures can be measured, only a few measurements
are easy and repeatable enough for widespread use. The most common are:Gestational Sac:The first element to be measurable is the gestation sac of the early pregnancy. The gestational sac is measured in three dimensions, and the average, the Mean Sac Diameter (MSD) used for estimating gestational age. It is useful between 5 and 8 menstrual weeks with accuracy of +/- 3 days . As a rough rule of thumb, the MSD + 30 = Menstrual Age in days. Embryonic Crown-Rump Length: The length of the embryo on the longest axis (excluding the yolk sac) constitutes the crown-rump length. This is among the best documented parameters to date the embryo, with accuracy of +/- 3-5 days. As a rough rule of thumb, the CRL + 6.5 = Menstrual Age in Weeks. Biparietal diameter (BPD): The transverse width of the head at it's widest. We measure from the the leading edge to leading edge of the bones, because this leading interface is most distinct. Since the head is oval, the error induced by small errors in positioning is small, making for a repeatable, robust measure. Head size is determined largely by brain growth which is relatively independent of nutritional (maternal/placental insufficiency) growth retarding processes, and head growth is often relatively "spared" in such growth retardation. The BPD best used after 12 weeks. Accuracy is +/- 1.1 week 14 - 20 weeks, +/- 1.6 weeks 20 - 26 weeks, +/- 2.4 week 26 - 30 weeks, and +/- 3 - 4 weeks after 30 weeks. Read More - http://www.baby2see.com/medical/charts.html |
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