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Protocol - Gestational Age - Medical Record Abstraction

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Description:

Gestational age is established using criteria for determination of estimated due date (EDD) adapted from the American Congress of Obstetricians and Gynecologists (ACOG), American Institute of Ultrasound in Medicine (AIUM), Society for Maternal-Fetal Medicine (SMFM), and Society of Obstetricians and Gynecologists of Canada (SOGC), and is denoted "project gestational age".

Protocol:

The first day of the last menstrual period (LMP) is determined, and a judgment made as to whether or not the patient has a certain or "sure" LMP date.

• Most charts will not identify a menstrual period as normal or entirely normal. Rather, what should be expected is a comment when things were not entirely normal (e.g., less flow than usual, irregular flow, history of irregular cycles, flow that did not occur when expected, etc.). The absence of such comments is sufficient to accept the LMP as entirely normal.

• If studies are designed prospectively and LMP is determined, the protocol should stipulate obtaining the following data: date of LMP, length of cycle, regularity of cycle, first cycle following discontinuation of contraception. For cycle lengths other than 28 days the EDD should be adjusted accordingly (i.e., if cycle length is 32 days, 4 days should be added to the calculated EDD prior to comparison with ultrasound. Similarly, if cycle length is 26 days, 2 days should be subtracted from the calculated EDD prior to comparison with ultrasound).

If the LMP date is uncertain, ultrasound measurement(s) obtained at the patient’s earliest ultrasound examination should be used to determine the project gestational age.

• If more than one first trimester ultrasounds are available, the earliest ultrasound with a crown rump length (CRL) equivalent to at least 7 weeks (or 10 mm) should be used (given the imprecision of measurement in very early scans).

• If the first dating ultrasound was conducted before 14 weeks 0 days, the measurement should be based on crown rump length (CRL) up to and including 84 mm and on BPD above 84 mm.

• For pregnancies of multiples the measurement of the largest fetus should be used.

If the LMP date is certain, and menstrual cycles have been regular, project gestational age is determined by a comparison between the gestational age by LMP and by ultrasound measurement.

• If more than one first trimester ultrasound is available, the earliest ultrasound with a crown rump length (CRL) equivalent to at least 7 weeks (or 10 mm) should be used (given the imprecision of measurement in very early scans).

• If the first dating ultrasound was conducted before 14 weeks 0 days, the measurement should be based on crown rump length (CRL) up to and including 84 mm and on BPD above 84 mm.

• For pregnancies of multiples the measurement of the largest fetus should be used for pregnancy dating.

• If the ultrasound confirms the gestational age by LMP (as in the table below) the LMP-derived gestational age is adopted as the project gestational age. Otherwise, the ultrasound derived gestational age is adopted as the project gestational age

Gestational age at first ultrasound by LMP

Ultrasound method of measurement

Ultrasound agreement with LMP

Up to and including 8 weeks 6 days

CRL

± 5 days

9 weeks 0 days to 13 weeks 6 days

CRL

± 7 days

14 weeks 0 days to 15 weeks 6 days

Per institution

± 7 days

16 weeks 0 days to 21 weeks 6 days

Per institution

± 10 days

22 weeks 0 days to 27 weeks 6 days

Per institution

± 14 days

28 weeks 0 days and beyond

Per institution

± 21 days

If the patient has undergone an assisted reproductive technique by in vitro fertilization to achieve pregnancy (standard IVF, IVF with donor egg, or IVF with ICSI) the IVF calculator should be used to estimate project EDC.

• the embryo is transferred at two days of age, the project EDC is 264 days after the date of transfer;

• the embryo is transferred at three days of age, the project EDC is 263 days after the date of transfer;

• the embryo is transferred at five days of age, the project EDC is 261 days after the date of transfer;

• the embryo is transferred at six days of age, the project EDC is 260 days after the date of transfer.

The following calculators may be used to determine project gestational age and project EDD once the principles detailed above have been followed:

EDD calculator

http://perinatology.com/calculators/Due-Date.htm

EDD from Ultrasound Report

http://www.perinatology.com/calculators/EDDSono.htm

Protocol Name from Source:

Project Gestational Age

Availability:

Publicly available

Personnel and Training Required

Personnel who are trained in performing medical records review.

Equipment Needs

None.

Requirements
Requirement CategoryRequired
Major equipment No
Specialized training No
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration

Medical record abstraction

Life Stage:

Adolescent, Adult, Pregnancy

Participants:

Pregnant women

Specific Instructions:

The "project EDD," which stems from the project gestational age, should not be revised once a determination has been made, except under unusual circumstances such as an obvious charting error.

If the pregnancy is conceived by in vitro fertilization, project gestational age is calculated from the date of embryo transfer and the embryo age at transfer (see below).

If the pregnancy is conceived spontaneously (including ovulation induction and artificial insemination) information from the earliest dating ultrasound and the last menstrual period are used to determine project gestational age as described below.

In the absence of a dating sonogram, the estimated due date (EDD) as determined by the last menstrual period (LMP) should be used, but note should be made that the gestational age estimate is "uncertain."

Because of the risk of re-dating a small fetus that may be growth restricted, decisions based on third-trimester (28 weeks, 0 days or later) ultrasonography alone are especially problematic and need to be guided by careful consideration of the entire clinical picture.

Should it not be feasible to determine gestational age via maternal chart review, maternal interview (Gestational Age - Maternal Interview) can be used instead, though this is less ideal given risk of recall bias. If maternal interview is used, questions adapted from the Extremely Low Gestational Age Newborns (ELGAN) study are recommended. Although the study focused on extremely low gestational age newborns, the PhenX Pregnancy Work Group members recommend it for use with any pregnancy.

Consideration should be given to using the following definitions developed by Workgroups of the U.S. National Institute of Child Health and Human Development:

Early pre-term - <34 weeks 0 days

Late pre-term - 34 weeks 0 days through 36 weeks 6 days

Early term - Gestational age 37 weeks 0 days through 38 weeks 6 days

Full term - 39 weeks 0 days through 40 weeks 6 days

Late term - 41 weeks 0 days through 41 weeks 6 days

Post term - over 42 weeks 0 days

Selection Rationale

This protocol has been developed using guidance from well-established international obstetrics and gynecology societies.

Language

English

Standards
StandardNameIDSource
Common Data Elements (CDE) Chart Abstraction Gestational Age Value 5633799 CDE Browser
Derived Variables

None

Process and Review

The Expert Review Panel has not reviewed this measure yet.

Source

Butt, K., & Lim, K.; Society of Obstetricians and Gynaecologists of Canada. (2014). Determination of gestational age by ultrasound. Journal of Obstetrics and Gynaecology Canada, 36(2), 171-183.

Committee on Obstetric Practice. (2014). American College of Obstetricians and Gynecologists Committee Opinion No. 611. Method for estimating due date. Obstetrics and Gynecology, 124, 863-866.

General References

Butt, K., & Lim, K.; Society of Obstetricians and Gynaecologists of Canada. (2014). Determination of gestational age by ultrasound. Journal of Obstetrics and Gynaecology Canada, 36(2), 171-183.

Committee on Obstetric Practice. (2014). American College of Obstetricians and Gynecologists Committee Opinion No. 611. Method for estimating due date. Obstetrics and Gynecology, 124, 863-866.

Raju, T. N., Higgins, R. D., Stark, A. R., & Leveno, K. J. (2006). Optimizing care and outcome for late-preterm (near-term) infants: A summary of the workshop sponsored by the National Institute of Child Health and Human Development. Pediatrics, 118(3), 1207-1214.

Spong, C. Y. (2013). Defining "term" pregnancy: Recommendations from defining "Term" Pregnancy Workgroup. JAMA, 309(23), 2445-2446.

Protocol ID:

240902

Variables:
Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
Research Domain Information
Measure Name:

Gestational Age

Release Date:

January 31, 2017

Definition

The period of time in weeks and days from the first day of the last menstrual period to the estimated date of delivery.

Purpose

Gestational age is an essential component of research on pregnancy outcomes. It is often used in research for stratification purposes, influences interpretation of many related measures, and is inversely associated with many neonatal complications.

Keywords

Pregnancy, prenatal, birthweight, due date, estimated due date, EDD, fertility, Extremely Low Gestational Age Newborns, ELGAN