Ok i will be 20 weeks on sunday....... im my What to expect while expecting book it says 5 months is from week 18 - 21 but i wanna say 5 months starts on the 20th week.... so my question.. how many months am i??

Here is my theory. If you are going by your period 5 mo=20 weeks, if you are going by gestation 5 mo=18 weeks. I don't know where the other numbers come from. You are actually pregnant for 40 weeks (10 months) so 20 weeks=5 months.

Last edited by blue_eyed_girl; 11-02-2005 at 10:29 AM.

When is your due date? That is by most people considered 9months - then count back. I am due on May 26, 2006 so I am just over 2 months. This is how my doctor explained it to me with each of my previous pregnancies.

The way I understand it, most books go by the lunar month which is the length of a typical cycle which is 28 days. Therefore 40 weeks of pregancy is considered 10 months. If you are calculating based on this system you would be 5 lunar months pregnant.

I've also read that pregnancy is 9 1/2 months which would be more around the 30 day month vs the 28th.

Go ahead and say you are 5 months. It just makes me feel better to round up as my belly grows!

The standard calculation is called Nagele’s Rule. This was developed in the 1850’s by a Dr. Nagele, who determined that the average human pregnancy was 266 days from conception, or 280 days (40 weeks) from the start of the last menstrual period. Divided into perfect four-week months, this comes out to ten perfect months. This is considered the "lunar" method.

also the weeks go by quicker than the months so this suits me well i am so impatient waiting for anything let alone something as important as having a baby

I am nearly 24 weeks pregnant and the doctor on the last viset at 22wk reffered to me as being in the sixth month counting it as 20-24 I guess, I know this calculation stuff has always thrown me too and this is my third successful pregnancy. LOL. I just stick with telling people the weeks most people know that a normal pregnancy last 40 weeks so its easier that way.... I am just glad to finally have the answer to the most famous question every one asks now (do you know the sex?) you can tell someone you are 12 weeks pregnant and that is still the first question, even though an ultrasound has no chance of telling you that yet.... Oh its a girl !!!!!

Ok, let me see if I can clear this up. There are two ways to "calculate" a due date. One is from the date of conception, and the other is from the FIRST day of your last period.

Since most women don't know the actual date of conception, the first day of your last period (LMP) is used as the calculation point, which means that 'technically' you are pregnant for two weeks BEFORE you concieve. You may hear your doctor refer to how many weeks pregnant you are, versus the fetal age. If calculated this way, the fetal age is two weeks YOUNGER then how many weeks pregnant you are. This is also why so many due dates change when you have a mid pregnancy ultra sound, because up until then the EDD was just that, an ESTIMATION. At this time your due date will change from LMP to the actual fetal age. Sometimes not, some doctors will just give women a two week window instead of an actual date (which I think is more acurate then a specific day).

If you calculate from the day of conception, pregnancy is 38 weeks long, since you are not factoring in the two weeks at the begining of your cycle when you were NOT fertile (which is not the time you likely concieved). If you had your due date given to you from an early dating scan, then your due date is most likely calculated by the fetal age, although if you counted or looked on a calculater, your due date would probably still be the end of the 40th week. 40 weeks is a good reference point so most doctors just go with that.

How anyone got 9 months is really beyond me. At best, it would be 9 and a half. When people refer to months they are calculated as being 28 days long. It doesn't matter if some months have 5 weeks, etc. A lunar month is 28 days, which again puts you at 10 months gestation, or if calculated by fetal age, 9 and a half.

For example, my due date is March 28th. Today I'm 19 weeks, 1 day.

The first day of a missed period, by the LMP method, would be one month of pregnancy, or 4 weeks. By fetal age, you are only two weeks pregnant.

The END of the 8th week is two whole months of pregnancy, 6 weeks fetal age, or a month and a half of pregnancy.

The END of the 12th week is three whole months of pregnancy, 10 weeks fetal age, or 2 and a half months. This also marks the end of the first of trimester.

The END of the 16th week is 4 whole months of pregnancy, 14 weeks fetal age, or 3 and a half months.

And so on and so forth.

So for me, being 19 weeks pregnant, I'm ALMOST finished by 5th month.

The 8th of November will be the completion of 5 months, and technically I'll be IN my sixth month, but that won't "count" as 6 months untill the end of the 24th week.

The 28th of March is the end of 40 weeks, which is 38 weeks since conception.

40 is a nice number, and has become the universal way of refering to pregnancy, so usually, regardless of fetal age or LMP, the weekly system is used to describe gestation. With this method, "months" are 4 weeks long, and go in 4 week incriments.

Does this help? Or am I just making it more confusing?