Pregnancy Week by Week — Weeks 4 to 40

Week by week

Follow every week of your pregnancy

Momly covers weeks 4 to 40. Each week explains how your baby is developing, what changes in your body, the symptoms that are common at that stage, plus nutrition and everyday tips — all from the app’s own guide content.

First trimester

Weeks 4–13

The first trimester is when the biggest changes often happen out of sight. The week pages in this section walk you through your baby’s earliest development steps, what is happening in your body, and the symptoms that are common in these early weeks.

Trimester 1poppy seed

Week 4

Size of a poppy seed

Your baby, now an embryo, is about 1-2 mm long, roughly the size of a poppy seed. It's growing quickly inside your uterus.

Trimester 1sesame seed or orange seed

Week 5

Size of a sesame seed or orange seed

This week your embryo is about 2 mm long, roughly the size of a sesame seed. It may look a little like a tadpole, with a primitive head structure and a small, tail-like protrusion. This is a very important week, when the foundations of the organ systems are being laid.

Trimester 1pea

Week 6

Size of a pea

Your baby, or embryo, is about 6 mm long, roughly the size and shape of a pea. With a curved back and a little tail, some people think it looks like a tiny tadpole.

Trimester 1blueberry

Week 7

Size of a blueberry

Your baby, or embryo, is now about half a centimeter long (roughly 10 mm from crown to rump); about the size of a blueberry. Your baby has grown remarkably fast compared to just a month ago.

Trimester 1raspberry

Week 8

Size of a raspberry

Your baby, now called a fetus, is about 1.6 cm long from crown to rump and weighs roughly 1 gram, about the size of a raspberry. Your little one will double in size by next week!

Trimester 1grape

Week 9

Size of a grape

Your baby, now called a fetus, is about 2.3 cm from crown to rump and weighs roughly 2 grams, about the size of a grape.

Trimester 1small tangerine

Week 10

Size of a small tangerine

Your baby, now officially a fetus, measures about 3.1 cm from crown to rump and weighs roughly 4 grams, about the size of a small tangerine.

Trimester 1fig

Week 11

Size of a fig

Your baby, now a fetus, measures about 4.1 cm from crown to rump and weighs roughly 7 grams, about the size of a fig. The head still looks large compared to the body, but the body keeps lengthening quickly.

Trimester 1lime

Week 12

Size of a lime

Your baby, now a fetus, measures about 5.4 cm from crown to rump and weighs roughly 14 grams, about the size of a lime.

Trimester 1pea pod

Week 13

Size of a pea pod

Your baby, now a fetus, measures about 7.4 cm from crown to rump and weighs roughly 23 grams—about the size of a pea pod.

Second trimester

Weeks 14–27

For many moms-to-be, the second trimester is the most comfortable stretch of pregnancy. These week pages cover your baby’s growth, the first movements, and the new changes in your body — together with nutrition and everyday tips.

Trimester 2lemon

Week 14

Size of a lemon

Your baby, now called a fetus, is about 14.7 cm from head to heel and weighs around 93 grams, roughly the size of a lemon.

Trimester 2apple

Week 15

Size of a apple

Your baby, now a fetus, measures about 16.7 cm from head to heel and weighs roughly 117 grams, about the size of an apple. In the coming weeks, that growth will become even more noticeable.

Trimester 2avocado

Week 16

Size of a avocado

Your baby, now a fetus, is about 18.6 cm long from head to heel and weighs around 146 grams, roughly the size of an avocado.

Trimester 2pear

Week 17

Size of a pear

Your baby, or fetus, is now about 20.4 cm from head to heel and weighs roughly 181 grams—about the size of a pear. Body fat is beginning to form, and it will keep building up right through to the end of your pregnancy.

Trimester 2bell pepper

Week 18

Size of a bell pepper

Your baby, or fetus, is now about 22.2 cm long from head to heel and weighs roughly 223 grams—about the size of a bell pepper.

Trimester 2mango

Week 19

Size of a mango

Your baby, now a fetus, measures about 24 cm from head to heel and weighs around 273 grams; roughly the size of a mango.

Trimester 2banana

Week 20

Size of a banana

Your baby, or fetus, is about 25.7 cm long from head to heel and weighs roughly 331 grams; about the size of a banana. While length measurements can vary from source to source, your baby keeps growing noticeably this week and still has room to move around in the womb.

Trimester 2carrot

Week 21

Size of a carrot

Your baby, or fetus, is now about 27.4 cm long from head to heel and weighs around 399 grams—roughly the size of a carrot.

Trimester 2papaya

Week 22

Size of a papaya

Your baby, now a fetus, is about 29 cm long from head to heel and weighs around 478 grams; roughly the size of a papaya.

Trimester 2grapefruit

Week 23

Size of a grapefruit

Your baby, or fetus, measures about 30.6 cm from head to heel and weighs around 568 grams, roughly the size of a grapefruit. In the coming weeks, weight gain will really pick up speed.

Trimester 2ear of corn

Week 24

Size of a ear of corn

Your baby, or fetus, is now about 32.2 cm long from head to heel and weighs around 670 grams — roughly the size of an ear of corn.

Trimester 2large potato

Week 25

Size of a large potato

Your baby, now a fetus, is about 33.7 cm long from head to heel and weighs around 785 grams, roughly the size of a large potato.

Trimester 2bunch of green onions

Week 26

Size of a bunch of green onions

Your baby, now a fetus, measures about 35.1 cm from head to heel and weighs roughly 913 grams, about the size of a bunch of green onions. As fat begins to build up beneath the skin, the body starts to look fuller and rounder.

Trimester 2cauliflower

Week 27

Size of a cauliflower

Your baby, or fetus, is now about 36.6 cm long from head to heel and weighs roughly 1.1 kilograms — about the size of a head of cauliflower.

Third trimester

Weeks 28–40

The final trimester brings both excitement and preparation. Week by week, this section follows how your baby gets ready for birth, what your body is doing, and what to keep an eye on as the big day approaches.

Trimester 3eggplant

Week 28

Size of a eggplant

Your baby, or fetus, is about 37.6 cm long from head to heel and weighs around 1.2 kilograms — roughly the size of an eggplant.

Trimester 3pumpkin

Week 29

Size of a pumpkin

Your baby, or fetus, is about 38.6 cm long from head to heel and weighs around 1.4 kilos, roughly the size of a pumpkin. They're now largely formed and will keep maturing their organs and putting on fat over the next few weeks.

Trimester 3cabbage

Week 30

Size of a cabbage

Your baby, or fetus, is about 39.9 cm long from head to heel and weighs roughly 1.6 kilos, about the size of a head of cabbage. Over the next seven weeks or so, you can expect your baby to gain around a quarter of a kilo each week.

Trimester 3coconut

Week 31

Size of a coconut

Your baby, or fetus, is now about 41.1 cm from head to heel and weighs around 1.8 kilos, roughly the size of a coconut. Between now and delivery, you can expect them to gain another 1.5 to 2.5 kilos or so.

Trimester 3turnip

Week 32

Size of a turnip

Your baby, or fetus, is about 42.4 cm long from head to heel and weighs around 2.0 kg — roughly the size of a turnip.

Trimester 3pineapple

Week 33

Size of a pineapple

Your baby, or fetus, is now about 43.7 cm long from head to heel and weighs around 2.2 kilos—roughly the size of a pineapple. Until delivery, your baby may keep gaining about a quarter kilo each week.

Trimester 3cantaloupe

Week 34

Size of a cantaloupe

Your baby, now a fetus, is about 45 cm long from head to heel and weighs around 2.4 kilos, roughly the size of a cantaloupe.

Trimester 3honeydew melon

Week 35

Size of a honeydew melon

Your baby, your fetus, is now about 46.2 cm from head to heel and weighs around 2.6 kg, roughly the size of a honeydew melon. Between now and your due date, your baby may gain anywhere from about half a kilo to a few extra kilos, a good deal of it baby fat.

Trimester 3head of lettuce

Week 36

Size of a head of lettuce

Your baby, or fetus, is now about 47.4 cm long and weighs roughly 2.8 kilograms, about the size of a head of lettuce. Growth may slow over the coming weeks, which lets your baby keep storing the energy needed for birth while also getting ready to pass through the narrow birth canal.

Trimester 3bunch of Swiss chard

Week 37

Size of a bunch of Swiss chard

Your baby, technically still a fetus, measures about 48.6 cm from head to heel and weighs roughly 3.0 kilos—about the size of a bunch of Swiss chard.

Trimester 3leek

Week 38

Size of a leek

Your baby, or fetus, measures about 49.8 cm from head to heel and weighs roughly 3.2 kilograms; about the size of a leek.

Trimester 3mini watermelon

Week 39

Size of a mini watermelon

Your baby, or fetus, is now about 50.7 cm long from head to heel and weighs around 3.4 kilos—roughly the size of a mini watermelon.

Trimester 3small pumpkin

Week 40

Size of a small pumpkin

Your baby, your fetus, is about 51.2 cm long from head to heel and weighs around 3.6 kilos, roughly the size of a small pumpkin.

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