US dating has been investigated in several studies, and biparietal diameter (BPD ) in the second trimester has been found to be superior to last. Crown-rump length may be used to accurately date pregnancy between 7 and 13 . Campbell was the first investigator to link fetal BPD to gestational age;. (gestational age, ultrasound biometry, ultrasound dating). Results were . for dating a pregnancy ABBREVIATIONS. AC abdominal circumference. ART.
Assessment of Gestational Age by Ultrasound | GLOWM
Clinical Considerations in the Second Trimester: Using a single ultrasound examination in the second trimester to assist in determination of gestational age enables simultaneous fetal anatomic evaluation. With rare exception, if a first trimester ultrasound examination was performed, especially one consistent with LMP dating, gestational age should not be adjusted based on a second-trimester ultrasound examination.
Ultrasound dating in the second trimester typically is based on regression formulas that incorporate variables such as; Biparietal diameter and head circumference measured in transverse section of the head at the level of the thalami and cavum septi pellucidi; the cerebellar hemispheres should not be visible in this scanning plane ; Femur length measured with full length of the bone perpendicular to the ultrasound beam, excluding the distal femoral epiphysis ; and Abdominal circumference measured in symmetrical, transverse round section at the skin line, with visualization of the vertebrae and in a plane with visualization of the stomach, umbilical vein, and portal sinus.
Other biometric variables, such as additional long bones and the transverse cerebellar diameter, also can play a role. Date changes for smaller discrepancies 10—14 days are appropriate based on how early in this second-trimester range the ultrasound examination was performed and on clinician assessment of LMP reliability.
Clinical Considerations in the Third Trimester: Because of the risk of redating a small fetus that may be growth restricted, management decisions based on third-trimester ultrasonography alone are especially problematic; they need to be guided by careful consideration of the entire clinical picture and may require closer surveillance, including repeat ultrasonography to ensure appropriate interval growth.
The best available data support adjusting the EDD of a pregnancy if the first ultrasonography in the pregnancy is performed in the third trimester and suggests a discrepancy in gestational dating of more than 21 days. As soon as data from the LMP, the first accurate ultrasound examination, or both are obtained, the gestational age and the EDD should be determined, discussed with the patient, and documented clearly in the medical record.
In most industrialised countries, ultrasound US is accepted as the method of choice, yet in the literature, 7- to day discrepancies are described. The discrepancy includes biological variation in the duration of pregnancy and methodological errors.
Estimating The Due Date – OBGYN Blog
US dating has been investigated in several studies, and biparietal diameter BPD in the second trimester has been found to be superior to last menstrual period LMP. In Denmark, an effort to standardise pregnancy dating has been made through the establishment of a national guideline.
This examination is a part of a free-of-charge prenatal programme combining age, biochemistry, and US screening for chromosomal abnormalities in the first trimester and a second trimester screening for malformations. However, this change has not yet been properly evaluated.
Previous studies of the use of BPD instead of LMP for dating show a reduced number defined as post-term pregnancies and thus a reduction of induction rates. Written informed consent was not required and therefore not obtained.
Estimating The Due Date
However, patients record and the data were anonymized before analysis. The population was an unselected population of pregnant women, and data were retrieved from the Astraia database www. The data were linked by the personal civil registration number with data from the Danish Medical Birth Registry, which contains data on the date of birth, birth weight and length, infant sex, number of infants born, intrauterine foetal death, pregnancy loss and complications during birth.