Pregnancy Week by Week: The Key Stages, Trimester by Trimester

At 8 weeks, your baby measures barely more than a centimetre. At 40, they weigh 3.4 kg on average. In between, following your pregnancy week by week means watching one transformation after another, for your baby and for you.

Rather than a separate, often repetitive page for each week, here are the essentials trimester by trimester: what is developing in your baby, what you may feel, and the appointments not to miss.

How to read this calendar

All weeks are given counted from the first day of your last period, as doctors do. In Morocco, your notes will show them as SA (semaines d'aménorrhée, weeks of amenorrhoea). Fertilisation happens at around 2 weeks: a baby "at 20 weeks" has therefore been developing for about 18 weeks. If you are unsure of your own count, our guide to working out how many weeks pregnant you are will help you find your place.

Unless stated otherwise, sizes during pregnancy are measured from head to bottom, as on a scan. They are averages: a healthy baby can be a little smaller or bigger.

First trimester (up to 14-15 weeks): everything takes shape

This is when the organs form, at great speed, while nothing shows on the outside yet.

For you. Tiredness, nausea, tender breasts and needing to pee often tend to dominate these weeks. Nausea is unpleasant but usually temporary: our tips for easing it are in our guide to pregnancy nausea.

Your appointments. A first antenatal visit during the first trimester, then the first scan, which dates the pregnancy and counts the embryos. French national health insurance places it during the 3rd month. What each examination involves is explained in our article on pregnancy scans.

Second trimester (15 to 28 weeks): the bump grows, baby moves

For many women, this is the most comfortable trimester: UNICEF notes that nausea and tiredness ease for most, while the bump starts to round out.

For you. A dark line may appear from the navel to the pubic bone, along with patches on the face, back or pelvic pain, tingling in the hands and sometimes the first stretch marks. The big moment is the first movements: usually around 17-18 weeks, more often between 18 and 20 weeks for a first baby, according to NHS Wales. First little flutters or bubbles, then clear kicks. Everything you need to know is in our article on when you feel your baby move.

Your appointments. Check-ups become monthly, and the second-trimester scan looks in detail at your baby's anatomy and growth. French health insurance places it in the 5th month; in the UK, it is offered between 18 weeks and 21 weeks plus 6 days.

Third trimester (28 weeks to birth): baby builds strength

Most of the organs are in place: your baby grows, matures and settles into the position they will be born in.

At birth, total length is around 46 to 51 cm, for a weight of just over 3 kg, according to UNICEF. Most women give birth between 38 and 41 weeks.

For you. Heartburn, breathlessness, haemorrhoids, swollen legs and ankles, broken nights: baby's weight presses on everything. Irregular contractions that tighten the bump or feel like period pain are common: these are Braxton Hicks contractions. Our practical solutions are gathered in the article on common pregnancy discomforts.

Your appointments. Check-ups become more frequent, and a last scan, during the 8th month in France, checks the baby's position and where the placenta lies. It is also time to prepare your hospital bag and baby's going-home outfit.

From the shop

Things to prepare, trimester by trimester

There is no hurry at the start. A pregnancy pillow becomes useful in the second trimester, the hospital bag and baby's going-home outfit in the third: here are a few ideas at different prices.

• −35 %DoomooSofty nursing pillow, Flower Yellow – Doomoo403 DHinstead of 620 DHView product
• −9 %DoomooBuddy nursing and maternity pillow, Classic Light Grey – Doomoo810 DHinstead of 890 DHView product
• −48 %Pasito a PasitoElodie maternity bag, blue – Pasito a Pasito676 DHinstead of 1 300 DHView product
• −41 %Walking MumArchie maternity bag – Walking Mum755 DHinstead of 1 290 DHView product
• −74 %Pureté du bébéEssentials velvet sleepsuit, girl, 1 month, beige, model 216 – Pureté du bébé164 DHinstead of 630 DHView product
• Mac IlusionTenderness 3-piece christening outfit, white, size 3 months – Mac Ilusion500 DHView product
• The whole aisle · Pregnancy and nursing pillows20 products online, delivered anywhere in Morocco.Open the aisle

Products sold by La Maison du Bébé, publisher of this magazine. Prices as of 12 October 2026; please check the product page.

From 28 weeks: go to sleep on your side

It is a simple step, backed by research. NHS Wales points out that, according to research, going to sleep on your back after 28 weeks doubles the risk of stillbirth. The safest position is on your side, left or right, it doesn't matter which. If you wake up on your back, there is no need to worry: simply turn onto your side. Our article on sleeping positions in pregnancy explains how to get comfortable.

Another rule for the second half of pregnancy: get to know your baby's usual pattern of movements. A baby moving less than usual is never something to "keep an eye on until tomorrow".

In Morocco: your own calendar

The exact rhythm of check-ups and tests depends on where you are followed, in a private practice, a clinic or a public health centre, and on your medical situation. Ask at your first visit for the schedule planned for you, and keep all your scan reports and test results in one folder: they will be invaluable for the team looking after you on the day of the birth.

If your pregnancy runs through the month of Ramadan, talk to your doctor early, before deciding whether or not to fast.