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). 40 weeks = 9 months ¦ 4.445 weeks = 1 month

For the Weeks to Months to Weeks Calculator - Convertor - Click here >>

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 period.

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.

Trimester Calculator

The three methods of calculating Trimesters are explained.

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

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

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

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

Personal timeline for your Pregnancy - Print out and Keep a copy in your purse!

	Back by popular demand! Yes it's back! - Many have asked if we could put back the 'Fetus weeks breakdown table' (above) as they found it easy to work out how the weeks, months and trimesters relate to each other. So we went into the archives and brought it back for you. It has now been added to the top of all the Fetus Development pages again, 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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Confusion starts here.

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 month is 30.4 days, a little over 4 weeks and 2 days long. A normal pregnancy is 40 weeks, or, little longer than nine average months.

Time 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 - Measured as nine months on the calendar. [ + extra 7 days for Duedate ]

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 +/- 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 - A lunar month is the time between two successive new moons or full moons. Lunar months approximate the mean length of approximately 29.53059 days (29 days, 12 hours, 44 minutes and 3 seconds).
280 days is approximately nine and half lunar months, since a lunar month is approximately 29.53 days long. When people claim that a pregnancy is exactly 10 lunar months, they are making the mistake of calculating a lunar month to be 28 days long.
Trimesters - From Latin trimestris from tri- ("three") + mestris ("month") '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 beginning, middle, and end.

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.

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 next three months will be a period of rapid growth.

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 9½ 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 40 weeks from the start of your LMP. Gestation 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 two months of pregnancy and include: Examination of uterine size Identification of audible fetal heart tones Ultrasound examination prior to 26 weeks from LMP 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:

Your LMP was March 1.
Add nine months, bringing you to December 1.
Add seven days, bringing you to your due date of December 8.
Thus, your due date becomes December 8.

Some people prefer to do it this way:

Your LMP was Feb 1
Add 1 day
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.

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

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

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

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Pregnancy Information from : www.Baby2see.com is intended for educational purposes only.
It is not intended to replace medical advice from your physician, doctor or health care professional.
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Weeks? Months? Trimesters? Lunar months? Days?

Back by popular demand!

Confusion starts here.

Time breakdowns for pregnancy

How long is pregnancy?

So when is my due date?

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You may have found this page by searching for "week 'X' is month 'X', pregnancy is how many months, when does trimester 'X' start, pregnancy weeks months trimesters breakdown chart" or similar terms.