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NCBI Bookshelf. Kenia I. Edwards ; Petr Itzhak. Authors Kenia I. Edwards 1 ; Petr Itzhak 2. Determining gestational age is one of the most critical aspects of providing quality prenatal care. Knowing the gestational age allows the obstetrician to provide care to the mother without compromising maternal or fetal status. It allows for the correct timing of management, such as administering steroids for fetal lung maturity, starting ASA therapy with a history of pre-eclampsia in pregnancies, starting hydroxyprogesterone caproate Makena for preterm deliveries.
An average pregnancy lasts days from the first day of the last menstrual period LMP or days after conception. It is prudent for the obstetrician to get a detailed menstrual history, including duration, flow, menstrual periods, and hormonal contraceptives. 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 the 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. The over-the-curve technique involves using a measuring tape Dating pregnancy long cycle centimeters from the superior aspect of the pubic symphysis to over the top of the uterine fundus.
Highly trained practitioners can palpate the uterine fundus as early as 12 weeks, commonly at the symphysis. Clinical landmarks approximate a week size gestation at the umbilicus, with a week size gestation at the halfway mark between the symphysis and the umbilicus.
For instance, if a patient has uterine fibroids, this can decrease the accuracy of this technique. For patients who have had a cesarean, the uterus is generally in a higher position because of pelvic adhesions. Other factors that decrease accuracy include body habitus, multiple gestations, and a retroverted uterus. Fetal heart tones are auscultated with the fetoscope at weeks. Electronic Doppler device can detect fetal heart tones as early as 8 to 10 weeks gestation.
Ultrasonography is best within Dating pregnancy long cycle first half of the pregnancy. An embryo is usually seen later between 5 to 6 weeks. Mean sac diameter MSD can be used early in gestation to estimate the due date if there is no embryo on the sonogram. To calculate the MSD, the diameter sac measurement must be in the perpendicular plane, with a mean of three measurements.
MSD increases by 1mm per day during early pregnancy. Given the large margin of error. MSD should not be used for final due date estimation. Additionally, anembryonic pregnancies can have a measurable MSD. CRL is the longest straight-line measurement of the embryo from the outer margin of the cephalic pole to the rump. The BPD measurement criteria include; an oval head shape instead of a round head shape, midline structures should be centered, measured at the level of the thalamus and cavum septum pellucidum, should not include top orbits.
The BPD measurement is from the outer edge of the proximal skull to the inner edge of the distal skull. The HC measurement criteria should include all those required for the BPD and is measured around the outer perimeter of the skull. The AC measurement criteria include; the abdomen should be round, not oval-shaped or squashed, true transverse image, images of ribs should be symmetrical on both sides, measured at the umbilical level vein s the portal sinus, calipers should go all the way to the skin surface.
The FL measurement criteria include; perpendicular to the direction of insonate, ends should be sharply visible, and measurement should exclude epiphyses. The margin of error is reduced depending on when i. After this range, variation in fetal size growth makes this less precise.
The same rules, as discussed above, apply to twins or higher-order gestations. If there is size discordance between the twins, the larger twin is used to calculate the EDD. The due date is determined by dates of ovulation, egg retrieval, insemination, cleavage stage, or blastocyst transfer. Assisted reproductive technology ART uses the principle of Naegle's Dating pregnancy long cycle as the foundation for estimating the due date.
If using a frozen embryo day 3EDD is days from the date of embryo transfer to for three days of embryo culture. If a day 5 blastocyst is implanted, add days to this date to calculate EDD. The determination of gestational age is vital to providing quality prenatal care. Establishing correct EDD is paramount in coordinating care between healthcare professionals that include a nurse, laboratory technologists, a pharmacist, and various physicians in different specialties.
This will allow timely laboratory testing since most of the pregnancy tests are time-sensitive. For example, fetal genetic abnormalities can be detected in a timely fashion providing the mother with sufficient time to make a lifetime decision. This book is distributed under the terms of the Creative Commons Attribution 4. Turn recording back on. National Center for Biotechnology InformationU.
StatPearls [Internet]. Search term. Estimated Date of Delivery Kenia I. Author Information Authors Kenia I. Affiliations 1 Nassau University Medical Center. Issues of Concern Clinical History and Physical Exam An average pregnancy lasts days from the first day of the last menstrual period LMP or days after conception.
Multi-fetal Gestations The same rules, as discussed above, apply to twins or higher-order gestations. Assisted or artificial conception The due date is determined by dates of ovulation, egg retrieval, insemination, Dating pregnancy long cycle stage, or blastocyst transfer. Clinical ificance The determination of gestational age is vital to providing quality prenatal care.
Knowing the gestational age allows appropriate care to the mother without compromising maternal or fetal status. Knowing the gestation age allows for the correct timing of management, such as administering steroids for fetal lung maturity, starting ASA therapy with a history of pre-eclampsia in pregnancies, and starting Makena for preterm deliveries. Nursing, Allied Health, and Interprofessional Team Interventions Establishing correct EDD is paramount in coordinating care between healthcare professionals that include a nurse, laboratory technologists, a pharmacist, and various physicians in different specialties.
Comment on this article. References 1. Obstet Gynecol. Estimated date of delivery based on second trimester fetal head circumference: A population-based validation of 21 deliveries. Acta Obstet Gynecol Scand. Naidu K, Fredlund KL. Gestational Age Assessment. Estimated Date of Delivery. In: StatPearls [Internet].
In this. Related information. PubMed Links to PubMed. Similar articles in PubMed. Unjustified increase in cost of care resulting from U. Predictors of response to alpha hydroxyprogesterone caproate for prevention of recurrent spontaneous preterm birth.
Am J Obstet Gynecol. Epub Dec Gestational age at initiation of alpha hydroxyprogesterone caproate and recurrent preterm birth. Epub May Review Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database Syst Rev. Epub Mar Review Adjuvant hydroxyprogesterone caproate in women with history-indicated cerclage: A systematic review and meta-analysis. Epub Nov Recent Activity.
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