Join NursingCenter to get uninterrupted access to this Article. Accurate determination of the estimated due date EDD during pregnancy has personal and social significance for the woman and her family, guides obstetric evaluation and intervention, and has research and public health consequences. Ultrasound measurement of the crown-rump length CRL in the first trimester is considered the most accurate estimator of the EDD. Once the EDD is determined it should be documented in the medical record and discussed with the patient. Although determination of the EDD is a responsibility of the obstetric provider, nurses should be aware of the process of standards-based determination of EDD to give the most accurate and current information to women and their families and to enhance the nurse’s advocacy role surrounding gestational age-based assessments and interventions. Obstetrics and Gynecology , 4 , Baskett T.
The best estimated delivery date EDD is determined by the date of the last menstrual period LMP if confirmed by early ultrasound. For deliveries resulting from the use of assisted reproductive technology, the best EDD is based on the known date of fertilization. Accurate pregnancy dating is important to improve outcomes and is a research and public health imperative. The best estimated due date should be documented clearly in the medical records. If the most recent gestational age is dated before the date of delivery, add the number of days between the most recent gestational age and the date of delivery to the gestational age estimate.
Gestational age Estimated from last menstrual periodActive. Term Description. Gestational age estimate based on date of first day of last menstrual.
Outline Assignment of Gestational Age, Fetal Weight Estimation and Weight Percentiles, In the first trimester, gestational age should be assigned to the pregnancy based on sonographic findings or mean sac diameter prior to the visualization of the embryo and by embryonic or fetal crown-rump length CRL thereafter. In the second trimester, gestational age should be assigned based on head measurements that take into account head shape—namely, the corrected biparietal diameter or head circumference HC —or a composite age formula.
By the latter part of the third trimester, neither dating by ultrasound nor dating by last menstrual period LMP is very accurate. Once gestational age has been assigned by an accurate method, such as sonography, the pregnancy should not be redated nor should the estimated due date be changed, because the earlier the gestational age is determined, the more accurate the dating of the pregnancy.
Estimating fetal growth is best performed through estimating fetal weight and weight percentile, starting in the latter part of the second trimester and during the third trimester.
Back to Your pregnancy and baby guide. Pregnancy normally lasts from 37 weeks to 42 weeks from the first day of your last period. Sign up for Start4Life’s pregnancy and baby emails for expert advice, videos and tips on pregnancy, birth and beyond. You can find pregnancy and baby apps and tools in the NHS apps library.
The Current Date is set to your local workstation date. EDC by LMP is calculated by adding days (40 weeks) to the first day of the last menstrual period.
To compare the accuracy of the reported date of the last menstrual period LMP with that of symphysis-fundal height SFH in the estimation of gestational age GA , using an ultrasound US scan as reference. Gestational age was concurrently assessed by the 3 methods in this prospective, population-based, pregnancy-outcome study conducted in Hyderabad, Pakistan, from June 18, , through August 31, , with women between 20 and 26 weeks of a singleton pregnancy.
Knowing gestational age GA accurately is essential for optimal prenatal, delivery, and postnatal care. The expected date of delivery, correct diagnosis of preterm or post-term labor, and differentiation between premature birth and intrauterine growth restriction rest on the estimated GA, as do prenatal counseling and interventions for poor fetal growth as well as the avoidance of unnecessary hospitalization, testing, and interventions such as induction of labor and tocolytic treatment [ 1 , 2 , 3 ].
Furthermore, a close estimation of GA informs research toward improving maternal and neonatal outcomes. And an accurately predicted delivery date PDD is obviously useful to the pregnant woman and her family. As a fetal ultrasound US scan is based on biometric measurements of the fetus, it is considered the gold standard for establishing GA when done before 20 weeks of gestation, when the biologic variations in fetal size and the effects of growth restriction are still small. The accuracy is less if the scan is performed during the third trimester [ 3 , 4 , 5 ].
In many high-resource countries, a first-trimester US scan and a second scan between 18 and 22 weeks are essential parts of obstetric practice because they establish GA and screen for fetal anomalies [ 3 , 6 ]. However, US equipment is often unavailable in low-resource countries, especially in rural and peri-urban areas. And where available, the equipment is expensive to use, often of poor quality, and operated by undertrained technicians.
In addition, women often seek prenatal care late in pregnancy, which further limits the use of ultrasound to assess GA [ 1 , 3 ].
Fetal Biometry and Growth
Estimates the gestational age of the pregnancy and displays weekly fetal development information, along with the due date. To embed this calculator, please copy this code and insert it into your desired page:. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.
Lastly, add 1 year and 7 days to that date. Due date calendar. For example: Your last menstrual period began on September 9, Counting back 3 calendar.
You can calculate your due date by subtracting three months from the first day of your last menstrual period LMP and then add a week. Use our pregnancy calculator. A pregnancy is based on being days long, which is 40 weeks more like 10 months not 9! When we give you a due date we consider 37 to 42 weeks to be full-term, so even if your baby is born two weeks before your due date it is not considered premature. Because few women know the exact day they ovulated or conceived, an ultrasound done in the first trimester of pregnancy has been shown to the be the most accurate way to date a pregnancy.
If an ultrasound date in the first trimester differs from your LMP date by seven days or more, we would go with the ultrasound.
Methods for Estimating the Due Date
Metrics details. Assessing gestational age by ultrasound can introduce a systematic bias due to sex differences in early growth. This cohort study included data on 1,, births recorded in the Swedish Medical Birth Register. As expected, adverse outcomes were lower in the later time period, but the reduction in prematurity-related morbidity was less marked for male than for female infants.
Date of last menstrual period (LMP): The baby will be born on or around: *Ovulation occurs approximately 2 weeks after the date of the last menstrual period.
Kenia I. Edwards ; Petr Itzhak. Edwards 1 ; Petr Itzhak 2. Determining gestational age is one of the most critical aspects of providing quality prenatal care. An average pregnancy lasts days from the first day of the last menstrual period LMP or days after conception. It is prudent of the obstetrician to get a detailed menstrual history including duration, flow, previous menstrual periods, and use of hormonal contraceptive. These factors are used to determine the length of her cycles and ovulation period.
First, a woman may not accurately recall the first day of her menstrual cycle. Third, there are small variations in duration between fertilization and blastocyst implantation. Last, this method cannot differentiate between menstrual bleeding and early pregnancy bleeding. Other clinical methods that can calculate EDD include uterine size by pelvic examination using the over-the-curve technique.
Standards-Based Determination of the Estimated Due Date
Read terms. Pettker, MD; James D. Goldberg, MD; and Yasser Y. This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed.
Dating based on LMP is fraught with inaccuracies, including incorrect recall, irregular menstrual cycles, menstrual cycles longer or shorter than
Context: High perinatal mortality in India may be caused by inaccurate dating of pregnancy resulting from suboptimal uptake of antenatal care and ultrasound services during pregnancy. Methods: Data from an ongoing cross-sectional screening program providing fetal radiology imaging in Guna district of Madhya Pradesh from — was analyzed for recall of LMP and discordance between LMP and ultrasound assigned EDD.
Results: The program screened 14, pregnant women of which 4, In , the project had no maternal deaths, infant mortality rate of Conclusion: Accurate dating of pregnancy and systematic follow-up integrating radiology imaging and obstetrics care for appropriate risk-based management of pregnant women can significantly improve perinatal statistics of India. Correspondence Address : Dr. Committee Opinion No Methods for estimating the due date. Obstet Gynecol ;e Prenatal diagnosis in Sweden to — A register-based study.
BMC Pregnancy Childbirth ;
When LMP and Ultrasound Dates Don’t Match: When to Redate?
Redating a pregnancy may occur when there is a discrepancy between the estimated due date EDD calculated by the last menstrual period LMP and that by ultrasound. Care should be taken when redating a pregnancy, especially in the third trimester, as there may be other reasons for a fetus to be small for gestational age e. According to the ACOG redating is more reliable using the earliest available and reliable ultrasound examination surrogates.
For instance, CRL in the first trimester would be more accurate than a debatable uncertain LMP or 2nd-trimester biometrics.
the main calculation method being the date of the last menstrual period (LMP) 2, and making possible the recording of gestational age infor- mation based on.
Colleague’s E-mail is Invalid. Your message has been successfully sent to your colleague. Save my selection. Pettker, MD; James D. Goldberg, MD; and Yasser Y. This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed.