Pregnancy calendar: how does it work week by week?

You’ve just found out you’re pregnant. Congratulations! And so begins the nine-month adventure that will lead you to the most beautiful of encounters. To navigate this period with full confidence, understand what is happening in your body, and anticipate the important stages, it’s time to familiarize yourself with the pregnancy calendar.

This calendar isn't just for the walls of OB-GYN offices. It’s your ally for decoding your pregnancy, week by week. It helps you know when your ultrasounds will be, understand why you feel strange at week 14, or simply feel a bit less lost when faced with all the medical terms thrown at you during consultations.

At Puissante, we believe that knowing your body and its transformations well is a superpower. So, we’re going to explain it all to you.

What you need to know about the pregnancy calendar

What is a pregnancy calendar?

A pregnancy calendar is a tracking tool that follows your pregnancy week by week. It starts counting from the first day of your last period (even before conception actually occurs, yes really!) and ends around 40 weeks.

The goal? To have clear benchmarks regarding your baby’s development, changes in your body, and essential medical appointments not to be missed. It is your roadmap for the 9 months ahead.

According to Inserm, the pregnancy calendar divides your pregnancy into distinct trimesters, each with its own challenges, baby movements, and key milestones. From a tiny embryo to the final preparations before birth, every week counts and brings something new.

Why use a pregnancy calendar

Good question! First off, it allows you to see the whole journey. Instead of experiencing your pregnancy week by week without really understanding where you are in the process, the pregnancy calendar gives you an overall vision. You know what to expect, when, and why.

Next, the pregnancy calendar facilitates communication with your healthcare provider. Instead of vaguely saying "I’m halfway there," you can say with precision, "I’m at 20 weeks of amenorrhea (WA)." This is extremely helpful for doctors and midwives to track your progress.

It also helps you anticipate exams, tests, and ultrasounds. You won't find yourself surprised during a consultation. You will know that at 12 weeks you’ll have your first ultrasound, that at 20 weeks you might (possibly) find out the baby’s sex, that at 7 months you need to think about your hospital bag…

Finally, and this is far from negligible, it allows you to better understand your symptoms. Having nausea at week 6? It’s normal, welcome to the club. Feeling kicks at week 18? That’s also completely normal. As the official portal Santé.fr explains, having the calendar in front of you means being able to say: "Ah, okay, that’s what those pregnancy articles are talking about."

Creating a pregnancy calendar: the guide

Weeks of amenorrhea (WA) vs weeks of pregnancy (WP): the real difference

Here, a quick side note that makes sense. There are two ways to count your pregnancy, and it can be confusing.

1. Weeks of amenorrhea (WA) start from the first day of your last period. You will hear this term in consultations, in articles, everywhere. It is the standard in France. Since ovulation occurs about 14 days after the first day of your period, there is a two-week gap between your actual conception and this count.

2. Weeks of pregnancy (WP) start from the day of conception. This is used less often in France, but it is logical: you are "truly" pregnant from that moment on, not before.

To give you a concrete example: if you are at 16 WA, you have actually been pregnant for 14 weeks. It’s no big deal if you mix them up a bit at the beginning. Your healthcare provider will explain it to you, and you will get used to it quickly.

The week-by-week journey: how it unfolds

The first trimester (weeks 1 to 13 WA) 

This is the time of major invisible transformations. The baby goes from a few cells to an embryo with a heart that has started beating. You, on the other hand, probably have nausea, strange fatigue, and an incessant urge to cry while watching a yogurt commercial. Welcome. At week 12, the first ultrasound takes place to see if everything is fine and to date the pregnancy precisely.

The second trimester (weeks 14 to 26 WA)

The nausea usually goes away (phew), and you start to have a real "pregnancy bump." The baby grows visibly, its organs develop, and around week 18-20, you will feel the first kicks. The second ultrasound gives you a very detailed image of your little one. This is also the time to start preparing yourself psychologically and physically for childbirth if you wish.

The third trimester (weeks 27 to 40+ WA) 

Time for the final preparations! The baby grows, its lungs finish developing, and he (or she) tries out different positions. You, meanwhile, probably feel contractions, fatigue that returns, and growing impatience. Around week 32, a third ultrasound checks the growth and position of the placenta. From 37 weeks, technically, the baby can be born without being considered "premature."

Key exams to remember

The pregnancy calendar doesn't exist just to give you fun facts. There are specific medical exams to be done at specific times, and the calendar is your memory aid.

• Blood tests at the beginning (blood type, infections, toxoplasmosis) and regularly throughout.

• First ultrasound around 12 WA.

• Second ultrasound around 20 WA (morphology, baby’s sex).

• Third ultrasound around 32 WA.

• Declaration of pregnancy to be done before the end of the 3rd month.

• Monthly consultations with your gynecologist, midwife, or general practitioner.

There are also optional screening tests (combined test, amniocentesis) that your professional will offer you if necessary. All these milestones help you verify that everything is going well for you and the baby.

Frequently asked questions about the pregnancy calendar

How many weeks does a pregnancy last?

A pregnancy lasts on average 40 weeks of amenorrhea, or about 9 months. But honestly, it’s more like 9 months and a week, since we start from the first day of the period and not from actual conception. And nature doesn't have a clock: some women give birth at 38 weeks, others at 41.

What is the difference between WA and WP?

There is a 2-week gap between WA and WP. If you are at 30 WA, you have actually been pregnant for 28 weeks. WA is the standard calculation in France; WP is rarely used here.

How do I know if I have passed my due date?

We speak of "post-term" when you reach 42 WA without having given birth. At this stage, your healthcare professional will want to induce labor for safety reasons. Until then, stay patient! Many children are born well before this limit.

When will I feel the baby move?

Generally between the 16th and 20th week, you will feel the first "kicks" or movements. But every woman is different. If you haven't felt anything by 20 weeks, don't panic, the ultrasound can confirm that everything is fine.

Are my dates likely to change after the ultrasound?

Yes, it’s possible. The first-trimester ultrasound is the most accurate (margin of error of 3 to 5 days). If the calendar you had was based only on the date of your last period, it might be slightly adjusted after the ultrasound. This is normal and harmless.

What happens if my cycle is irregular?

If your cycles are very irregular, the calculation based on the last period will be less reliable. Fortunately, the first-trimester ultrasound resets the counter with precision, so you will quickly be clear about your true dates.

Discover our advice for better tracking your menstrual cycle. 

When can I resume a normal life?

You can continue a completely "normal" life during your pregnancy: working, exercising (appropriately), having sex, using a vibrator… The pregnancy calendar helps you identify if you need specific adjustments at certain times, but the majority of women experience a perfectly ordinary pregnancy.

What signs should alert me?

No matter where you are in your calendar, go to the hospital if you experience: 

• bleeding, 

• intense abdominal pain, 

• severe symptoms of nausea/vomiting, 

• loss of consciousness, 

• or a sudden decrease in baby’s movements.

The pregnancy calendar really is your friend during these nine months. By having a clear vision of what is happening, you gain confidence and autonomy. And that is what female empowerment is: knowing your body, understanding your pregnancy, and being able to communicate as an equal with your healthcare provider.

So, keep this calendar handy. Reread it regularly. And never hesitate to ask your doctor or midwife questions if something puzzles you. Your pregnancy is your story. It’s up to you to master it.