Gestational Age calculation formula method.pdf
- 1. Dr Musa GESTATIONAL AGE CALCULATION It is well known that medical Community is rather reluctant to accept such mathematical formulae. But with repeated use, when their simplicity is realised, such formulae become part of the clinical practice as shown in past by formulas for calculating Total Dose Iron (TDI) requirement; electrolytes (Na+, K+, etc) requirement in cases or their deficiencies - etc. If the period of amenorrhoea involves the month of February, for the sake of accuracy 2 days (3 if it is leap year) should be subtracted from the above calculation. CONCLUSION The formula described for most accurate calculation of Gestational Age (GA) i.e Gestational Age G.A. = 4(M) weeks + 5(M)/2 (or 5(M) x 1/2) days where 'M' is the period of amenorrhoea in months appears to be more accurate than previously existing methods and being a simple mental calculation, the method spares the obstetrician of a calculating device Ex. 1 - LMP on 20.12.2023, to calculate G.A. on 10.08.2024 for case of calculation, we calculate the period from 20.12.2023 to 10.08.24 number of months = (current date - LMP) = 10.08.2024 - 20.12.2023 = 21days + 7 months so, M = 7 Gestational Age G.A. = 4(M) weeks + 5(M)/2 days +21days = 4(7) weeks + 5(7)/2 days +21days = 28weeks + 35/2days + 21days = 28weeks + 17.5days + 21days = 28weeks + 38.5days = 28weeks + 5weeks + 3.3days = 33weeks 3.3days Or Calculating from 20.12.23 to 20.08.24 to achieve complete month Month elapse = (Current date - LMP) = 20.08.24 - 20.12.23
- 2. Dr Musa = 8month Gestational Age GA = 4(M) weeks + 5(M)/2 days = 4(8) weeks + 5(8)/2 days = 32weeks + 40/2days = 32weeks + 20days But Current date 10.08.24 is 10days before 20.08.24 hence subtract 10day Gestational Age GA = 32weeks + 20days - 10days = 32weeks + 10days = 32weeks + 1week + 3days = 33weeks 3days METHOD 2 Using 4 тЕУ Formula Besides the Naegele formula, there is one more formula that you can use to calculate the age of the foetus in the womb, namely the 4 тЕУ formula. This is an example of applying the formula. Gestational Age G.A. = {(Current date тАУ LMP) x (4 тЕУ)} An example of a calculation scenario is as follows: Today is August 10th, 2024. Mother-to-beтАЩs LMP falls on December 20th, 2023 That means: Gestational Age = {(10.08.2024 - 20.12.2023) x (4 тЕУ) = 21days + 7months x (4 1/3) + 0years = 21days + 91/3weeks = 21days + 30weeks + 2.3day = 3weeks + 30weeks + 2.3days = 33weeks 2.3days Days are subtracted from days; months are subtracted from months, and years from years Multiplication is only done in months. Days donтАЩt need to be multiplied by 4 тЕУ
- 3. Dr Musa So the gestational age in the data above is 33 weeks 2days Or Calculating from 20.12.23 to 20.08.24 Months = (Current date - LMP) = 20.08.24 - 20.08.23 = 8months Gestational age GA = 4 1/3 x (M) weeks = 4 1/3 x (8) weeks = 104/3 weeks = 34. 7weeks 1week = 7days 0.7weeks = 0.7weeks x 7days/1weeks = 4.9days = 5days Gestational Age = 34weeks + 5days Current date 10.8.24 is 10days before 20.08.24 ie 1weeks 3days True gestational age = (34weeks +5days) - (1weeks + 3days) = 33weeks 2days It is undeniable that the formula for calculating gestational age using the 4 тЕУ methods is a little more complex than the previous method. However, this method can also be used as a benchmark for obtaining EDD METHOD 3 Calculate gestation age within 15-30sec off head 1month Pregnancy - 4weeks 3days 2month pregnant - 8weeks 5days 3months pregnant - 13weeks 0days 4months pregnant - 17weeks 3days
- 4. Dr Musa 5months pregnant - 21weeks 5days 6month pregnant - 26weeks 0days 7month pregnant - 30weeks 3days 8months pregnant - 34weeks 5days 9months pregnant - 39weeks 0days LMP 20th December 2023. Current date 10th August 2024 From 20.12.23 to 20.08.24 is 8months 8months pregnancy is 34weeks 5days But Current date is 10.8.2023 which is 10days less than 20.08.24 Therefore Gestational age = 34weeks + 5days - 10days = 33weeks 2days