Conflicting information - when does the 2nd trimester start?

[Maruschke]

Ok I know it is not really that important but...

Three different sites have told me three different things! The starting date of the second trimester is

12w1d, 13w1d, 14w0d. What the?

Does anyone know for sure when it starts? I want to be excited and feel like I have passed a milestone but I am not sure when it is.

Also.... some sites say that when you are 12w3d, that you are 13 weeks. Is this right? I would say 12 weeks.

Again, it is not really important, just frustrating! And when I track bean's development over time I would like to be looking at the information for the right week!

[Kailani]

Hmm, I was of the understanding that second trimester began at 13 weeks.

[Antheia]

I have always thought it was when you hit 13 weeks too.

[Heaven]

I think it begins at 13 weeks.

With the what week to look at thing, it's confusing. If you are 12w3d than you are 12 weeks pregnant but you are in your 13th week iykwim? Coz for the first week you are 0 weeks pregnant yet but you are in your first week. So look at the wording e.g. if it says 12 weeks pregnant or week 12 of pregnancy. Some of them have an explanation down the bottom of the page. But I find the fertility friend pregnancy one the best coz it knows exactly where you're up to from your chart and gives you the right info. You have to pay for that tho if you want it.

Here's a taste for you lol (for where you are now)

The crown-to-rump length of your baby is about 1.25 to 1.68 inches (between 3.1 and 4.2cm). He weighs about 0.18 ounces (5g).
The placenta is now producing progesterone which helps to make nutrients for your developing baby.
Your baby has passed the stage when he is most susceptible to damage. By the end of this week, the danger zone for congenital abnormalities has passed.
The plan for your baby's body has been completely laid down by now. Further growth and cell division will build on this plan.
Taste and tooth buds have appeared.
Your baby has recently developed fingers and toes which are now well-formed. Ankles, wrists and the inner ear have formed. Your baby's nose is flat and his eyes are far apart. His eyes, ears, mouth and nose are all recognizable. The tail is disappearing.
Your baby is moving around the amniotic sac, and moving his feet and ankles. You still will not be able to feel these movements but you may be able to see them on an ultrasound.
Blood is circulating through the arteries and the vein of the umbilical cord.
The brain of your baby is developing at a phenomenal rate. About one quarter of a million new neurons are produced every single minute at this stage in your pregnancy.
If your baby is a boy, his testes, though they are not even clearly visible, are already producing testosterone.
Your baby is no longer called an embryo, but rather a fetus.

Your uterus is now about the size of an orange, but you still don't "show". However, you probably have noticed an increase in your breast size.
You may be having mood swings, feeling happy and elated one moment, crying the next. This is perfectly normal, caused by the changing hormones in your body as well as all the hopes and fears you have and the realization that your life will be forever changed by your pregnancy.
There is little increase in abdominal size during the first trimester, though you might be starting to see some weight gain. Hormonal changes, however, especially the increase of progesterone and relaxin can cause your joints and ligaments to soften as your body begins to prepare for birth.
The joints in your pelvic bones are widening now. This may cause you to feel unstable at times, even sometimes dropping things or bumping into things.

[[M]umma[M]ia]

day 1 in 13 weeks is when trimester 2 starts!!

[butterfly_warrior]

The conflict arises because there are three different ways of counting trimesters.

One way is to look at development. This way, 2nd trimester starts at 12 weeks and 3rd starts at 27 weeks.

Another is by gestation - this simply divides the 40 weeks of pregnancy into three equal stages, which gives 2nd trimester starting at 13 weeks and 3 days. 3rd trimester starts at 26 weeks and 5 days this way.

The third is by conception - take the 38 weeks of pregnancy that occur after conception and divide that into three equal stages. This way gives 2nd trimester starting at 14 weeks and 5 days, while 3rd trimester starts at 27 weeks and 3 days.

The third trimester dates all seem to fall pretty close together at around 27 weeks, which is why I guess the conflict doesn't seem to arise there, but there are vastly different dates for second trimester. Averaging them out gives something around 13 weeks, but information will vary as to which method was actually used to calculate them.

BW

[2CheekyMonkeys]

i always thought it was 13 weeks cause you just completed your 12th week (know what i mean? ) but then i just went by the blurb on the second trimester forum on here which starts at 14.