Week 4
Poppy seed
1 mm · <1 g
Implantation. The blastocyst becomes an embryo.
Week by week
From poppy seed to pumpkin — 36 weeks of growth. Set your due date on the home page to highlight your current week.
Week 4
1 mm · <1 g
Implantation. The blastocyst becomes an embryo.
Week 5
2 mm · <1 g
Heart begins to form and beat faintly.
Week 6
5 mm · <1 g
Facial features and limb buds appear.
Week 7
1 cm · <1 g
Brain grows fast; arms and legs lengthen.
Week 8
1.6 cm · 1 g
Now officially a fetus. Fingers webbed.
Week 9
2.3 cm · 2 g
Tiny muscles allow first movements.
Week 10
3.1 cm · 4 g
Vital organs are all present.
Week 11
4.1 cm · 7 g
Fingernails begin to form.
Week 12
5.4 cm · 14 g
Reflexes kick in; can open and close fists.
Week 13
7.4 cm · 23 g
Vocal cords develop.
Week 14
8.7 cm · 43 g
Facial expressions begin — squinting, frowning.
Week 15
10 cm · 70 g
Can sense light through eyelids.
Week 16
12 cm · 100 g
Tiny bones in the ears — may hear your voice.
Week 17
13 cm · 140 g
Fat starts to form under the skin.
Week 18
14 cm · 190 g
You may feel first flutters (quickening).
Week 19
15 cm · 240 g
Vernix (protective coating) forms.
Week 20
25 cm · 300 g
Halfway there. Anatomy scan around now.
Week 21
27 cm · 360 g
Movements become more coordinated.
Week 22
28 cm · 430 g
Eyebrows and lips are well defined.
Week 23
29 cm · 500 g
Skin is red and wrinkled — muscle forming.
Week 24
30 cm · 600 g
Viability milestone with NICU support.
Week 25
34 cm · 660 g
Hair color and texture developing.
Week 26
35 cm · 760 g
Eyes open; startle reflex present.
Week 27
36 cm · 875 g
Brain activity resembles a newborn's.
Week 28
37 cm · 1 kg
Third trimester begins. REM sleep observed.
Week 29
38 cm · 1.15 kg
Bones fully developed but still soft.
Week 30
40 cm · 1.3 kg
Amniotic fluid begins to decrease.
Week 31
41 cm · 1.5 kg
All 5 senses functioning.
Week 32
42 cm · 1.7 kg
Practices breathing motions.
Week 33
43 cm · 1.9 kg
Skull still soft to ease birth.
Week 34
45 cm · 2.15 kg
Central nervous system maturing.
Week 35
46 cm · 2.4 kg
Kidneys fully developed.
Week 36
47 cm · 2.6 kg
Considered early term next week.
Week 37
48 cm · 2.85 kg
Early term. Practicing sucking & grasping.
Week 38
49 cm · 3.1 kg
Vernix and lanugo mostly shed.
Week 39
50 cm · 3.3 kg
Full term. Brain grows rapidly still.
Week 40
51 cm · 3.5 kg
Due date week. Any day now.
Set your due date to highlight your current week automatically.