Ultrasonography has advanced obstetric practice by enabling relatively detailed assessment of the fetus, including an accurate estimate of. The estimation of pregnancy dates is important for the mother, who Conceptional age (CA) is the true fetal age and refers to the length For example, with an LMP beginning on June 15, the EDD will be March 22 of the following year. The introduction of obstetric ultrasonography in the early s led. As pregnancy progresses, accurate and optimal pregnancy dating is important knowledge of the gestational age for an accurate assessment of lab values. Ultrasound has been used in obstetrics for over 50 years and is.
Pregnancy, Dating - StatPearls - NCBI Bookshelf
Color doppler is particularly indispensible in the diagnosis of fetal cardiac and blood vessel defectsand in the assessment of the hemodynamic responses to fetal hypoxia and anemia. A more recent development is the Power Doppler Doppler angiography. It uses amplitude information from doppler signals rather than flow velocity information to visualize slow flow in smaller blood vessels. A color perfusion-like display of a particular organ such as the placenta overlapping on the 2-D image can be very nicely depicted.
Doppler examinations can be performed abdominally and via the transvaginal route. The power emitted by a doppler device is greater than that used in a conventional 2-D scan. Its use in early pregnancy is therefore cautioned. Doppler facilities are generally an integral part of modern ultrasound scanners.
They merely would need to be switched on to function. One does not need to 'go' to another machine for the doppler investigations. This information is vital for timing of appropriate obstetric care; scheduling and interpretation of certain antepartum tests; determining the appropriateness of fetal growth; and designing interventions to prevent preterm births, postterm births, and related morbidities.
Appropriately performed obstetric ultrasonography has been shown to accurately determine fetal gestational age 1. A consistent and exacting approach to accurate dating is also a research and public health imperative because of the influence of dating on investigational protocols and vital statistics.
This Committee Opinion outlines a standardized approach to estimate gestational age and the anticipated due date. However, there is great usefulness in having a single, uniform standard within and between institutions that have access to high-quality ultrasonography as most, if not all, U. Accordingly, in creating recommendations and the associated summary table, single-point cutoffs were chosen based on expert review. Because this practice assumes a regular menstrual cycle of 28 days, with ovulation occurring on the 14th day after the beginning of the menstrual cycle, this practice does not account for inaccurate recall of the LMP, irregularities in cycle length, or variability in the timing of ovulation.
It has been reported that approximately one half of women accurately recall their LMP 2—4. Accurate determination of gestational age can positively affect pregnancy outcomes.
For instance, one study found a reduction in the need for postterm inductions in a group of women randomized to receive routine first-trimester ultrasonography compared with women who received only second-trimester ultrasonography 5.
A Cochrane review concluded that ultrasonography can reduce the need for postterm induction and lead to earlier detection of multiple gestations 6. Because decisions to change the EDD significantly affect pregnancy management, their implications should be discussed with patients and recorded in the medical record.
Measurements of the CRL are more accurate the earlier in the first trimester that ultrasonography is performed 11, 15— The measurement used for dating should be the mean of three discrete CRL measurements when possible and should be obtained in a true midsagittal plane, with the genital tubercle and fetal spine longitudinally in view and the maximum length from cranium to caudal rump measured as a straight line 8, Mean sac diameter measurements are not recommended for estimating the due date.
Dating changes for smaller discrepancies are appropriate based on how early in the first trimester the ultrasound examination was performed and clinical assessment of the reliability of the LMP date Table 1. For example, for a day-5 embryo, the EDD would be days from the embryo replacement date. Likewise, the EDD for a day-3 embryo would be days from the embryo replacement date. Clinical Considerations in the Second Trimester Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation.
Estimated date of delivery - Wikipedia
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. Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as the 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 the femur length measured with full length of the bone perpendicular to the ultrasound beam, excluding the distal femoral epiphysis the 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 8 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. 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; therefore, decisions need to be guided by careful consideration of the entire clinical picture and may require close 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.
Estimated date of delivery
Variability[ edit ] Distribution of gestational age at childbirth among singleton live births, given both when gestational age is estimated by first trimester ultrasound and directly by last menstrual period. The median is merely a guideline for the day at which half of all births occur earlier, and half of all births occur later. Births rarely occur on a due date, but they are clustered around due dates.
The rule estimates the expected date of delivery EDD by adding a year, subtracting three months, and adding seven days to the origin of gestational age.
Methods for Estimating the Due Date - ACOG
The result is approximately days 40 weeks from the start of the last menstrual period. Another method is by adding 9 months and 7 days to the first day of the last menstrual period. Naegele's rule is named after Franz Karl Naegele —the German obstetrician who devised the rule. InNaegele became ordinary professor and director of the lying-in hospital in Heidelberg.
His Lehrbuch der Geburtshilfe, published in for midwives, enjoyed a successful 14 editions.