👶 Gestational age

Current week of pregnancy and trimester.

⚠️ Gestational age is measured from LMP, not from conception. For accurate evaluation, consult your obstetrician.

Weekly development guide

Week	What's happening
4	Implantation in the uterus is complete. The embryo is the size of a poppy seed.
5	The heart begins to beat - at roughly twice your rate.
6	The neural tube - the basis of brain and spinal cord - is forming.
7	Hands and feet are sketched out as small paddles.
8	The embryo becomes a fetus. All major organs are present in rudimentary form.
9	Fingers appear. The heart already has 4 chambers.
10	Primitive motor coordination starts - baby can flex limbs.
11	Fingernails begin to grow.
12	End of the first trimester. Simple reflexes appear.
13	Vocal cords form - silently, since amniotic fluid prevents vibration.
14	Sex becomes visible on ultrasound.
15	Baby can suck their thumb.
16	Hearing begins to develop.
17	Lanugo (fine body hair) appears on the skin.
18	Movements become perceptible to the mother.
19	The neural network for the five senses is developing.
20	Halfway. Time for the anatomy scan (morphology ultrasound).
21	Baby is "swallowing" amniotic fluid, practicing digestion.
22	Eyebrows and eyelashes appear.
23	Hearing responds to external sounds - talk, sing, read.
24	Viability threshold (with intensive care).
25	Responds to light - can see a diffuse glow if you shine a flashlight on your belly.
26	Lungs start producing surfactant.
27	End of trimester 2. Baby has sleep-wake cycles.
28	Trimester 3 begins. Rapid fat accumulation.
29	Muscles and lungs mature quickly.
30	Space gets tight - fewer but stronger movements.
31	The immune system is preparing for life outside.
32	Baby settles head-down.
33	Bones harden (except the skull - still pliable).
34	Lung age: nearly mature.
35	Nails reach the fingertips.
36	Average weight: 2.7 kg.
37	Full term. Baby is ready.
38	Reflexes are complete.
39	Protective fat layer is complete.
40	Official due week. Only 5% of births happen exactly on the due date.