Pregnancy due date and gestational age
Gestational age and estimated date of delivery from LMP, ultrasound, or IVF transfer date.
About this calculator
Pregnancy gestational age and estimated due date (EDD) calculation. Standard per ACOG Committee Opinion 700 (2017, reaffirmed 2024). Three methods based on data accuracy. Naegele's rule from LMP. EDD = first day of last menstrual period + 280 days (40 weeks). Used when menses are regular (28-day cycle), the patient recalls exact LMP, and there was no hormonal contraception in the past 3 months. For cycles longer than 28 days add the difference: 30-day cycle – +2 days, 35-day – +7 days. Ultrasound dating. First-trimester ultrasound (between 7+0 and 13+6 weeks) is the gold standard. Crown-rump length (CRL) is measured, EDD calculated by Robinson-Fleming. If discrepancy with LMP-based date exceeds 5-7 days (depending on gestational age), EDD is reset to ultrasound. Accuracy ±5 days in T1, ±10 days T2, ±21 days T3. Known conception date (IVF, ovulation). With known embryo transfer or ovulation date: EDD = conception date + 266 days. Used after IVF or with ovulation testing during planned conception. Clinical use. Planning first- and second-trimester screening. Marker of pregnancy progression. Postdate management (>=41+0 weeks) – induction or expectant. Linked to gestational age calculation for fetal growth assessment, small-for-gestational-age, preterm labor. Limitations. Accuracy declines with gestation – T2-T3 ultrasound dating is less precise. In patients with irregular cycles, after IVF, or with uncertain LMP – first-trimester ultrasound is mandatory. Modern EDD via date calculators without ultrasound confirmation is a rough guide; clinical decisions need confirmation.
Source
Formula version: naegele-acog-2024-v1
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