Pregnancy Length 
  

Pregnancy Length

Months? Lunar months? Weeks? Days? Trimesters?
9 months 40 weeks 280 days



  

Weeks? Months? Trimesters? Lunar months? Days?

 
The charts below show how the weeks, months and trimesters break down into each other.

If you are confused, you're not alone. While some people talk about pregnancy being 9 months long (divided into three trimesters), most health care providers refer to pregnancy as being 40 weeks long, starting with your last menstrual period (LMP).weeks months convertor

40 weeks = 9 months + 1 week      4.4 weeks = 1 month

A normal pregnancy lasts 280 days from your LMP which is about 266 days from conception to birth. The first two weeks of your pregnancy includes the time of your period, ovulation and fertilization. Conception occurs approximately 14 - 16 days after the first day of your last menstrual period (LMP).

The date of conception is not always known and can vary between women. The date of LMP is known by most women so doctors use this date as a starting point for pregnancy. From your LMP they will add 280 days and this will give your Estimated Due Date or EDD. In general, all doctors agree that pregnancies, when using the LMP dating technique, average approximately 280 days or 40 weeks.


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Trimesters calculator
Trimester Calculator

The three methods of calculating Trimesters are explained.

Pregnancy time line

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The charts below show how the weeks, months and trimesters break down into each other.
Have you seen the twin of this chart ?
Last seen near Massachusetts, United States
10:45 PM (Apr 28, 2011)
with pregnant female (5 months)  A.K.A. First-time-mom
  ¶:o)

*This is just a guideline and the exact weekly breakdown may differ from source to source.
Weeks 1 - 4 5 - 8 9 - 13 14 - 17 18 - 21 22 - 26 27 - 30 31 - 35 36 - 40
Which
Month
are you in?
You are
in your
first
month
You are
in your
second
month
You are
in your
third
month
You are
in your
fourth
month
You are
in your
fifth
month
You are
in your
sixth
month
You are
in your
seventh
month
You are
in your
eighth
month
You are
in your
ninth
month
.
This is
Month
one two three four five six seven eight nine
Trimester first second third

Example:
  in Week 15  =  you are in your 4th Month    and    Month 4 is in your Second Trimester
[ So - You have completed three months  and  are now into your fourth month ]
Think like your age:-   You are 28 and have completed 28 years, you are in your 29th year.

The most common weeks to months breakdown used for the 9 months of pregnancy:
*This is just a guideline and the exact weekly breakdown may differ from source to source.

Your First Trimester:
1st Month = Weeks 1,2,3,4  
2nd Month = Weeks 5,6,7,8  
3rd Month = Weeks 9,10,11,12,13
Your Second Trimester:
4th Month = Wks 14,15,16,17
5th Month = Wks 18,19,20,21
6th Month = Wks 22,23,24,25,26
Your Third Trimester:
7th Month = Wks 27,28,29,30
8th Month = Wks 31,32,33,34,35
9th Month = Wks 36,37,38,39,40
Week 1 till end of week 13Begin week 14 till end week 26Begin week 27 till Birth
* As used on Baby2see.com

The most common trimesters breakdown used for the 9 months of pregnancy:

First Trimester ends 13 weeks + 3 days   ~   Second Trimester ends 26 weeks + 6 days


Personal timeline for your Pregnancy - Print out and Keep a copy in your purse!
Shows you a personal breakdown of the months and % of pregnancy completed.

Trimester Calculator - The three basic methods of calculating trimesters are explained.

Pregnancy Tests Schedule and quick guide to some of the routine tests used in pregnancy.


 
  

Week by week pregnancy information table

Many find it easy to work out how the weeks, months and trimesters relate to each other on the table above; this has now been added to the top of all the Fetus Development pages, so you can click a week, a month or trimester to see what your little one will be doing in your 'bump' at that stage.

 

Convert weeks to months  Calculate: Pregnancy weeks >> months >> weeks
Trimester Calculator - How the trimesters are calculated is explained.
 convert pregnancy weeks into months
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9 months or 10 - Confusion starts here.

Although it may be confusing at first, health care providers begin counting the pregnancy from day one of the last known menstrual period. Yes, that is about 14 - 16 days before you even conceived.

There is often confusion when some try to convert weeks into months and count a month as 4 weeks. February is the only month with just 4 weeks. The average calendar month is 30.4 days, a little over 4 weeks and 2 days long. A normal pregnancy is 40 weeks, or, a little longer than nine average months.

NOTE:
Several years ago World health organizations made an attempt for a universal lunar months method to measure pregnancy length [i.e. 28 days = 1 month x 10 = 10 months pregnant] but; this was not accepted world-wide. This has just made the confusion worse, with some health care providers using the 10 lunar months method now, while others do not.

 

Timeline breakdowns for pregnancy

  • Days - 280 days from your LMP (Gestational) or 266 days from conception to birth (Fetal age).

  • Weeks - 40 weeks from the start of your LMP (Gestational).
                 38 weeks from conception to birth (Fetal age).

    Most doctors count pregnancy weeks from LMP (Gestational), a few others may count from conception to birth (Fetal age); and the week numbers may vary.
    Example: Week 28 (Gestational) = Week 26 (Fetal age)

    One thing to note is - four weeks from the first day of your last period you are considered "4 weeks pregnant", but, "in week 5 of pregnancy". This can get confusing, especially considering that your baby is actually, only about two weeks old.

  • Months [ Calendar ] - Measured as nine months on the calendar + extra 7 days for Duedate. According to the Gregorian calendar, where months range from 28 - 31 days, this means the average pregnancy lasts a little over nine months.

    Examples: Whichever one is easier for you -

    Example 1 -- starting one week after your LMP
    LMP = January 1st + 7 days = January 8th   + 9 calendar months = October 8th [Duedate]

    Example 2 -- add one week on the end
    LMP = January 1st + 9 calendar months = October 1st  + 7 days = October 8th [Duedate]

    Note: Always count the full months from the first day of your last period, like you would count the number of years in your age ie. in your first year you were 0, in your second year you were 1 year old, etc.   eg. LMP = January 1st ~ on February 1st you are 1 month pregnant, on March 1st you are 2 months pregnant etc.

    Interesting triva: 3 calendar months = 13 weeks.   Go on, try it!
    Take a calendar, pick any date, count forward 13 weeks, this will get you to 3 calendar months (minus a day) from where you started.

    eg. July 1st + 13 weeks, gets to September 30th, 1 day short of the 3 calendar months. Pick March 10th, + 13 weeks, gets to June 9th, again 1 day short of the 3 calendar months.

    - if the months you choose includes February, you get 2 days short of the 3 calendar months, except leap years, when again it is 1 day.

  • Lunar Months [ True ] - A true lunar month is the time between two successive new moons or full moons. Lunar months mean length is approximately 29.53059 days (29 days, 12 hours, 44 minutes and 3 seconds). 280 days Gestation is approximately nine and a half true lunar months, since a lunar month is approximately 29.53 days long.

  • Lunar Months [ Pregnancy ] - In some countries (mainly Far-East) pregnancy is counted using lunar months of exactly 28 days (i.e. 4 weeks), then 40 weeks = 10 months.

    In Japan, the normal length of a full-term pregnancy is considered to be 10 months, and not 9. The Japanese belief that a pregnancy lasts ten months refers back to their original calendar that used these shorter months. To confuse things further, the classical phrase used in Japan for a pregnancy is 'totsuki tooka', which refers to a length of ten months plus ten days.

    Some Asian countries in the Far-East did not incorporate the Gregorian calendar until the late eighteen hundreds, the Chinese did not start until 1912.

  • Trimesters - From Latin trimestris; from tri- ("three") + mestris ("months") 'three months'.
    Three periods of three months each. Months 1, 2 and 3 are the first trimester, months 4, 5 and 6 are the second trimester, and months 7, 8 and 9 are the third trimester.

    Most commonly, the first trimester is defined as from LMP through to end week 13.
    The second trimester is from week 14 through to end week 26.
    And the third trimester is from week 27 through to labor/delivery, which varies considerably but averages at week 40.
    13weeks + 13weeks + 13weeks = 39weeks   + 1week = 40weeks

Most health care providers will actually talk about your pregnancy in weeks, rather than months or trimesters. Nevertheless, some health care providers and pregnant women talk about the three trimesters to help give the pregnancy a time-scale; related closely to the important stages of fetal development, and also a beginningmiddle,  and end.
  • Beginning
    In the first trimester the embryo undergoes most of its early structural development. Most miscarriages occur during this period, the placenta will takes over hormone production around week 12 from the corpus luteum. Sometimes, the failure of the corpus luteum to adequately support the pregnancy with progesterone can result in an early pregnancy loss.
  • Middle
    In the second trimester the embryo, now known as a fetus, is recognisable as human in form, but is not developed enough to be viable if born. The first three months were a period of rapid development, the middle three months are a period of rapid growth.
  • End
    In the third trimester the fetus reaches viability, and may survive if born prematurely.


Trimester Calculator - The three basic methods of calculating trimesters are explained.

No matter what method is used; the date you will be given for when your baby will arrive is officially called your estimated date of confinement (EDC), your estimated date of birth (EDB) or estimated due date (EDD). This is more popularly called your 'due date'.

Even an estimated due date is nothing more than a estimate. Only 10% of women deliver on the estimated due date. Half of women hit the due date within one week, but 90% deliver within two weeks of the predicted due date. This is why some obstetricians have started predicting 'due weeks' instead of 'due dates'.

Your 'date' may be revised by health care providers during your pregnancy. Your baby's development is on a strict schedule during the first trimester. The fetus CRL (Crown to Rump Length) and the EHR (Embryonic Heart Rate) are accurate estimators of fetus age in the first trimester. CRL and EHR are measured at your ultrasound scans, the fetus age should be within + or - 1 week of your LMP.

No matter how you measure your pregnancy, even the best estimated due date can be inaccurate. So, although the waiting and uncertainty of not knowing exactly when your baby is to arrive can be unnerving, the best plan is to stay flexible and to always be prepared for the unexpected.

Your baby will be born when he or she is ready.


Fetal growth charts and tables for: - CRL - BPD - OFD - HC - HL - FL scan measurements.
 
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Fetal Development guides -- Week by Week -- Month by Month -- Trimesters

Due Date and Fetal Development Weeks Calculator for your pregnancy weeks.

Calculate and print out a personal Time line for your Pregnancy.

Conception Calculator estimates probable conception dates from Birth, LMP and Due dates.

Trimester Calculator - The methods of calculating trimesters are explained.

 
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How long is pregnancy?

 
The average pregnancy lasts 266 days, or 38 weeks, or 9 months. But, according to the calendar used by medical professionals, you will be pregnant for 280 days, or 40 weeks, or 9 months. When your pregnancy is dated using a 40 week calendar your baby's age is called 'Gestational age', but your baby to be will actually be about two weeks younger than that. Conception to birth is about 38 weeks and 'Fetal age' is what his or her actual age is called.

Q: This all sounds fine, but if you calculate the due date from LMP, are you counting weeks before conception?
A: Yes a Pregnancy lasts about 40 weeks from the start of your LMP, and is 38 weeks from conception to birth. Although it may be confusing at first, health care providers begin counting the pregnancy from day one of the LMP. Yes, that is about 2 weeks before you even conceived.

Physicians and midwives start the pregnancy clock on the first day of a woman's last menstrual period (LMP). Some women may be unable to recall their LMP or have very irregular or infrequent cycles. When you visit your care provider, try to give as close an estimate as possible. The closer the estimate, the less likely you will worry or experience stress if your baby does not come on the EDD. Only about ten percent of expecting moms deliver on their EDD anyway.

An experienced practitioner will also rely on physical clues to determine the baby's due date. These clues are most evident within the first few months of pregnancy and include:

Recent studies have shown that mothers carrying their first child have pregnancies averaging 41 weeks and one day. For subsequent pregnancies, the average duration is 40 weeks and three days.  In general, doctors agree that all pregnancies, when using the LMP dating technique, average approximately 280 days or 40 weeks.

 
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So when is my due date?

 
The traditional way to calculate a due date is to add 9 months from the first day of your LMP (last normal menstrual period) and then add seven days.

For example:

  1. Your LMP was March 1.
  2. Add nine months, bringing you to December 1.
  3. Add seven days, bringing you to your due date of December 8.
  4. Thus, your due date becomes December 8.
Some people prefer to do it this way:
  1. Your LMP was Feb 1
  2. Add 1 day
  3. On your calendar, count forward 40 weeks to determine your due date.
Making matters even worse, many women do not have typical 28-day cycles.
Practitioners may adjust the EDD to reflect the shorter or longer cycle length.

Remember, calculation of your due date is certainly not precise (after all, women get pregnant in all the months of the calendar, some of which have 28, 29, 30 and 31 days!).

Also, all women do not have a 'typical' 28 day cycle!

This is why your due date is usually referred to as your Estimated Due Date or EDD.

Use: the Due Date Calculator to estimate your due date.

or   Due Date and Fetal Development Weeks Calculator for your pregnancy weeks by week.

Calculate and print out a personal Time line for your Pregnancy - keep a copy in your purse!

Conception Calculator estimates probable conceive dates from Birth, LMP and Due dates.

 




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