# Goal/Experiment:
The goal of this protocol is to develop a reliable algorithm for assessing the gestational age of a newborn at birth. This is achieved through the use of either the mother's last menstrual period (LMP) or an obstetric ultrasound conducted early in the pregnancy. The aim is to standardize and automate the process to provide the most accurate estimate of gestational age at birth.
# Algorithm for Gestational Age Assessment at Birth
**Authors**: Zilma Reis, Juliano de Souza Gaspar, Sara Oliveira Elias, Regina Amelia Lopes Pessoa De Aguiar
**Institution**: Universidade Federal de Minas Gerais
**Published**: Jan 16, 2020
**DOI**: [10.17504/protocols.io.bawbifan](http://dx.doi.org/10.17504/protocols.io.bawbifan)
## Abstract
This protocol presents an algorithm for gestational age assessment when a reliable last menstrual period or an obstetric ultrasound is available in the birth scenario. A software was developed to automatically process data entries into the best estimate of the gestational age at birth.
It shall be used by the multicenter team of researchers, duly trained in accordance with the Good Clinical Practice Protocol, during the enrollment of newborns. This protocol is complementary documentation for scientific publications related to the clinical trials.
Relevant Clinical Trials:
- "Prematurity detection evaluating interaction between the skin of the newborn and light: protocol for the preemie-test multicenter clinical trial in Brazilian hospitals to validate a new medical device." Register number: [RBR-3f5bm5](http://ensaiosclinicos.gov.br/rg/RBR-3f5bm5).
- "Premature or small for gestational age? International multicenter trial protocol for classification of the low birth weight newborn through the optical properties of the skin." Register number: [RBR33rnjf](http://ensaiosclinicos.gov.br/rg/RBR33rnjf).
## Guidelines
The scientific references for the best recommendation to assist gestational age calculation at birth were:
1. Committee on Obstetric Practice, the Society for Maternal-Fetal Medicine. Committee Opinion No 700: Methods for estimating the due date. Obstet Gynecol. 2017;129(5):e150-4. PMID: 28426621. DOI: [10.1097/AOG.0000000000002046](http://dx.doi.org/10.1097/AOG.0000000000002046).
2. Papageorghiou AT, Kennedy SH, Salomon LJ, et al. International standards for early fetal size and pregnancy dating based on ultrasound measurement of crown-rump length in the first trimester of pregnancy. Ultrasound Obstet Gynecol 2014;44:641-8. DOI: [10.1002/uog.13448](http://dx.doi.org/10.1002/uog.13448).
3. Nguyen TH, Larsen T, Engholm G, et al. Increased adverse pregnancy outcomes with unreliable last menstruation. Obstet Gynecol 2000;95(6 Pt 1):867-73. DOI: [10.1016/s0029-7844(99)00639-0](http://dx.doi.org/10.1016/s0029-7844(99)00639-0).
## Materials
- **Reagents and Equipment:**
- Standardized Clinical Trial Data Collection Form
- Tablet for data collection
## Safety Warnings
- Ensure that patient consent forms are completed.
- Obtain necessary ethical approvals for conducting the research.
## Before Starting
Researchers should identify and prepare to interview the woman if she is conscious and agrees to participate in the study. Sources of data to assist in determining gestational age should include antenatal obstetric ultrasound reports with their images and medical records from prenatal care.
## Methodology
### 1. Menstrual Cycle Reference
#### 1.1 The Last Menstrual Period (LMP) Reference
The interview aims to qualify the information about the last menstrual period, in terms of its reliability.
- **Documentary Analysis**:
- When did your last menstrual period occur? Please confirm if it was the first day of menstruation.
- Are you sure about this date?
- Are your menstrual cycles regular? Clarify if the cycle duration did not change for more than one week.
- Two months before your last menstrual period, did you use any contraceptive method (pills, injections, Mirena IUD, skin implant, vaginal ring)?
- Two months before your last menstrual period, had you had an abortion or delivered a child?
- **Further Verification**:
- Take a picture of the personal prenatal care book where the LMP is reported to verify the accuracy.
### 2. Ultrasound Reference
#### 2.1 The First Obstetric Ultrasound Reference
Assess the best antenatal ultrasound record to determine gestational age. The assessment should occur between 7 weeks 0 days and 13 weeks 6 days of pregnancy, and the crown-rump-length (CRL) of the embryo is the primary reference.
- Chronologically organize the antenatal obstetric ultrasound reports.
- Select the first gestational assessment with an available CRL measurement between 7w+0d and 13w+6d.
- Take note of the assessment date and reported gestational age.
- Verify the CRL measurement, using the International Fetal Size standard for early pregnancy to adjust the gestational age accordingly.
### 3. Gestational Age Assessment, According to an Automated Algorithm
- Use software to process pregnancy dating at birth, following best practices for gestational age calculation.
The algorithm automates methods as follows:
- **Adjustment of CRL to the Intergrowth-21st Reference**: Based on international standards (Papageorghiou AT et al., 2014).
- **Reliable Last Menstrual Period Concept**: Addressing increased adverse pregnancy outcomes with unreliable LMP (Nguyen TH et al., 2000).
- **Gestational Age Assisted by CRL or LMP**: According to recommendations by the Committee on Obstetric Practice (2017).
#### 3.1 Data Collection
Insert the following details into the information system:
| Variable | Data | Details |
|-----------------|------------------------------------------------|-----------------|
| LMP_Date | Date of the last menstrual period | Date |
| LMP_1 | Question 1 | Yes/No |
| LMP_2 | Question 2 | Yes/No |
| LMP_3 | Question 3 | Yes/No |
| LMP_4 | Question 4 | Yes/No |
| LMP_5 | Question 5 | Yes/No |
| LMP_GA_Days | Number of days between the LMP_Date and Childbirth_Date | Date |
| US_CRL | Crown-rump-length (mm) reported in the ultrasound | Value |
| GA_CRL | Gestational age reported in the ultrasound (days) | Value |
| Childbirth_Date | Date of the childbirth | Date |
| US_Date | Date of the reference obstetric ultrasound | Date |
| US_GA | Gestational age reported in the ultrasound (days) | Value |
| DIFF | Day difference by LMP and US days of pregnancy | Value |
| DB_Intergrowth | Database with Intergrowth's CRL standard curves | Reference values|
#### 3.2 Decision-tree Details
Refer to the algorithm's decision tree for handling different data points regarding LMP and ultrasound measurements.
### 4. Experts Checking and Adjustments
Researchers are required to recheck data, referring to sources such as photos of ultrasound reports, digital images of the crown-rump length measurement, and copies of personal prenatal care records. Gestational age data should be validated against registered information.
Once validation is complete, the algorithm will process the optimal dating for gestational age at birth.
## Conclusion
This protocol provides a systematic process to determine the gestational age of a newborn at birth reliably. The accuracy of the assessment is enhanced by integrating data from two primary sources: the last menstrual period and early obstetric ultrasound measurements.
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