Menstrual history Indirect measure of conception of roughly 280 days Reliability depends and influenced by - recall of memory - presence of light bleeding - regularity of cycles - OCP, breast feeding etc Nichols C. Most women may round off the dates or tell preferred dates May lead to misclassification as post term pregnancy Naegeles revisited 19th century Frederiech Naegele original article in German textbook Naegele himself credits Harmann Boerhaave with Inventing the formula for EDD. Comparison of pregnancy dating by last menstrual period, ultrasound scanning and their combination. 2002;160-1666 Methods of determining the gestational age Parameter variability 2SDIVF 1 day Ovulation 3 days IUI 3 days Single I/C 4 days 1st trimester examn 2 weeks2nd trimester examn 4 weeks3rd trimester examn 6 weeks Callen PW.
No-one doubts that you know when your last period was.
What may have happened is that in the particular cycle that you conceived, you ovulated later (or earlier) than usual, which is not at all uncommon.
Pregnancy lasts an average of 280 days (40 weeks) from the first day of your last menstrual period (LMP).
The first day of your LMP is considered day 1 of pregnancy, even though you probably didn't conceive until about two weeks later (fetal development lags two weeks behind your pregnancy dates).
How long pregnancy lasts varies somewhat between women.
The due date toward which you have been working is based on pregnancy lasting 40 weeks or 280 days from the date of the last menstrual period (LMP).accurate dating of pregnancy at times becomes difficult especially in the presence of conflicting menstrual data and patient presenting for late ultrasound, this ppt explores the ways to arrive at a correct due week or date in such a scenario do we mature early? A London-based study of over 122 000 pregnancies with spontaneous onset of labour Roshni R Patel1,2, Philip Steer3, Pat Doyle1, Mark P Little4 and Paul Elliott4 IJE vol.33 no.1 107-113 © International Epidemiological Association 2004; all rights reserved. The median gestational age at delivery was 39 weeks in Blacks and Asians and 40 weeks in white Europeans. Menstrual age Overestimates the gestational age Wilcox M et al BMJ 1993;307(6904):588-91 10-45% do not provide correct information 18% with certain dates have significant difference with USG age Geirsson et al, Br J Obstet Gynaecol. Naegeles’ rule does not correlate with actual conception date…. Meconium stained amniotic fluid, which is a sign of fetal maturity, was statistically significantly more frequent in preterm Black and Asian infants and term Black infants compared with white European infants. Baird et al498 normal cycles luteal phase 7-19 days 10% ovulate on D14 Wicox et alonly 30% of normal cycle women are fertile between 10-17 days 50% pregnancy are unintended LMP recall is error prone Indian Husbands more aware of their wives’ LMP! Here the second trimester begins at 12w 0d and the third at 27w 0d.With this method you take the 40 weeks of gestation and divide into three equal stages.The other way to calculate your due date is to use a pregnancy wheel. It’s very easy to estimate your due date if you have access to a pregnancy wheel. When you line up that date with the indicator, the wheel will display your due date. Luckily, there are ways to figure out your due date when you can't remember the first day of your LMP.