Ultrasound dating pregnancy
Outcomes: To determine whether ultrasound dating provides more accurate gestational age assessment than menstrual dating with or without the use of ultrasound.To provide maternity health care providers and researchers with evidence-based guidelines for the assignment of gestational age.With today's modern equipment, we can obtain very reliable images and measurements of even very early pregnancies, sometimes even seeing a heartbeat as early as 5-6 weeks!The most common misconception we encounter almost daily, has to do with how accurate ultrasounds are in fixing the EDC at different stages of pregnancy.Even when the last period is known, ultrasound is reassuring to demonstrate adequate growth, especially when there’s a risk of delayed growth, as in hypertension or smoking, or if there’s the risk of exaggerated growth, as in gestational diabetes.It is not uncommon for babies that are labeled “Large for Gestational Age (LGA)” and “Intra Uterine Growth Restriction (IUGR)” to have monthly or even weekly ultrasounds during the pregnancy.However, if you have a larger than average baby, the ultrasound will apply the husky figures to the “normal” measurements.
Of all of these uses, dating the pregnancy is the most common reason to use ultrasound, particularly when the expectant mother cannot remember the date of her last period (as in breast-feeding or irregular cycles).
Five dating methods: LMP, FH, US and their combinations, were assessed against the actual day of delivery (ADD).
The main outcome measures were: (i) the days between the ADD and estimated date of delivery in pregnancies where spontaneous labour occurred and the baby had a normal birth weight; (ii) the incidence of gestational age-related outcomes; and (iii) the influence of clinical variables on dating discrepancies. The accuracy of dating was similar for certain and uncertain LMP. US-based dating was most accurate (for 85% of predictions within 14 days) and similarly accurate at 20 - 24 weeks and at Pregnancy dating by US, including those in more advanced pregnancies than currently permitted, is recommended since all non-ultrasound-based estimations of gestational age were considerably less accurate.
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