Sociedad de Obstetricia y Ginecologa

The use of multiple parameters improved the accuracy of gestational age assessment compared with any single parameter ( table 11 ). Paired BPD measurements at different gestational ages allows categorization of the specific cranial growth patterns.

  1. Measurement of the fetal abdominal circumference (AC) is in the TRANS-axial view of the fetal abdomen.
  2. 80 If the gestational age estimates derived from all the parameters are similar, assignment of gestational age from the average of all the parameters will improve the accuracy.
  3. The first BPD measurement is not the fetus with large, medium or small BPD growth, and thus, the fetus can distinguish is associated with a mean gestational age based on an assumed average BPD growth pattern.
  4. 74 Tangential section of the femur, if you can visualize the entire length of the shaft, leads to underestimation of FL and thus the gestational age.
  5. SUMMARY A simple but consistent approach should be applied to the assessment of gestational age, in all the fetuses.

In addition, FL measurements in the axial plane (parallel to the ultrasonic beam) have less mean absolute error than those in the lateral plane which is perpendicular to the ultrasonic beam (1.7 mm compared to 3.7 mm, respectively). At 5 to 6 weeks of pregnancy, the different sites, it can not always be determined, but also the heart movement can be detected in the rule, Central. The technique consists in the measurement of the fetal length from the tip of the cranial pole of the tip of the caudal pole..

After 12 weeks of gestation excessive curvature of the fetus may lead to erroneous shortening of CRL measurement; therefore, other measurements such as the biparietal diameter should be used to estimate gestational age. Fig. In General, ultrasound-derived fetal dating tables can be used for singleton pregnancies, accurately for twin pregnancies until approximately 30 weeks of pregnancy.

  1. The gestational age can be more accurately predicted by obtaining paired measurements (the first from 20 to 26 weeks of gestation and the second from 31 to 33 weeks ‘ gestation) and assigning gestational age by a method developed by Sabbagha and staff 79 the so-called growth-adjusted sonographic age (GASA).
  2. Reprinted with permission of the American College of obstetricians and gynecologists) head circumference..
  3. Right decisions in relation to suspected preterm or postdate pregnancies are only possible when gestational age is accurately estimated.
  4. The abdominal circumference can be calculated using these diameters or measured directly.
  5. 2.
  6. B.
  7. Ultrasound assessment of fetal age is based on the first ultrasound examination, provided the measurement is technically adequate.
  8. But the possible error of this method in the third trimester of pregnancy may not be acceptable.
  9. representation of the TRANS-axial ultrasound image of the fetal abdomen at the level of the abdominal circumference measurement of the fetal spine ( curved arrow) of the umbilical portion of the left portal vein ( solid arrow ), and the fetal stomach ( open arrow ) of the FEMUR LENGTH.
  10. 82, 83, 84, 85, 86 During the last 10 weeks of pregnancy there is a decrease in the rate of growth of twin fetuses compared with singleton fetuses.

Ultrasound image of a fetus at 10 weeks of pregnancy. Biological variation, for example, can occur due to differences in maternal age, parity, prepregnancy weight, geographic location and the specific characteristics of the population. Interpretation of antenatal biophysical testing (non-stress tests and biophysical profiles) may be subject to fluctuations, with the gestational age, as well.

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3). The reasons for the use of multiple parameters for fetal dating is that when two or more parameters predict the same end point, the probability of correctly predicting that end point is increased. Fetal heart rate reactivity and fetal breathing develop with advancing gestational age; therefore, the absence of these biophysical parameters may be interpreted as abnormal for fetuses in whom the gestational age has been overestimated. Similarly, the timing of repeat cesarean section requires accurate assessment of the data. A second BPD measurement 10 weeks later, the determination of the fetus is so large ( 90 percentile), average (between the 10 th and 90 th percentiles), or small ( 10th percentile) and lead to a more accurate assessment of fetal age. ultrasound image with biparietal diameter measurement ( solid arrows, the outer edge and the inner edge ) and the fronto-occipital diameter measurement ( between the open arrows ). The gestational SAC is imaged first in the longitudinal plane, obtaining long axis and anteroposterior measurements perpendicular to each other. 3. 3). Measurement of the AC is performed in the same manner as the HC, that is, by (1) tracing the outer perimeter of the AC by the trackball on the ultrasonic equipment or by digitizer or (2) the same equation as for HC using transverse and anteroposterior diameter of the fetal abdomen.. The first measurement should be obtained should be between 20 and 26 weeks of pregnancy, and the second measurement, between 30 and 33 weeks of pregnancy. Campbell was the first investigator to link fetal BPD to gestational age 20; however, since this original report, which appeared in numerous publications on this topic in the literature. First-Trimester assessment In the first trimester, gestational SAC mean diameter and crown-rump length are used, the fetal age.

  • In pregnancy with unknown menstrual dates or a discrepancy between the menstrual dates and the mean gestational age predicted by multiple parameters of more than 3 weeks, the fetal age should be estimated by the multi-Parameter method.
  • Gestational age estimations in twin pregnancies should be performed before 30 weeks of pregnancy, in a similar manner to that for singleton pregnancies.
  • biological variation and technical factors that may contribute to the inaccuracy of the AC measurements in a manner similar to that previously described for the bi-parietal diameter.
  • 20, 21, 22, 23, 24, 25, 26, 27, 28, 58, 59, 60, 61, 62, 63 The BPD may be rapidly and reproducibly measured by ultrasound examination from 12 weeks gestation until the end of the pregnancy.
  • A.
  • 1).
  • 58, 59 Although several methods have been used to measure, the most commonly accepted method is measurement from leading edge to leading edge (outer-inner) (Fig.

4, 5 ultrasound is a reliable method for the determination of the length of the pregnancy and may improve obstetric care. The fetal growth assessment, either clinically or by ultrasound evaluation, also relies on the accurate determination of the gestational age. Of the plurality of parameters, the method of assessment of gestational age is valid if the gestational age estimates of the various ultrasound parameters are similar. The sac is measured inside the hyperechoic rim, including only the echo-free space (Fig. (Sabbagha RE, Barton BA, Barton FB et al: Sonar biparietal diameter: I. The BPD is imaged in the transaxial plane of the fetal head at a level depicting thalami in the midline, equidistant from the temporoparietal bones and usually the cavum septum pellucidum anteriorly (Fig. Fig. TRANS-axial image of the fetal head for biparietal diameter and head circumference measurements.

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