Pregnancy week by week

What's happening this week?

Slide through the weeks, or enter your due date to jump to yours. Each week shows your baby's size and what's developing, and which routine visits usually happen around then.

Week 12

Week 4Week 20Week 41

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Enter your due date.

About 2.1 in

about 0.5 oz

Week 12 · first trimester

About the size of a lime

Reflexes are developing: fingers open and close and the baby can curl its toes. The kidneys have started making urine.

Around now: first-trimester screening (optional).

With your due date saved, CycleHelm gives you each week in full, what to do, and what to ask at your visits. See how

The shape of a pregnancy

The first trimester is when everything forms: by the end of week 10 the major organs are in place, and from then on the work is growing and maturing. The second trimester is often the easiest stretch, with energy back and the first movements. The third is growth, and lungs and brain getting ready for the outside.

Visits through the weeks

First prenatal visit, weeks 8 to 10: Health history, blood and urine tests, confirming the due date, often an early ultrasound.
First-trimester screening (optional), weeks 10 to 13: Cell-free DNA blood test from week 10 and the nuchal translucency scan between weeks 11 and 14, if you choose them.
Anatomy scan, weeks 18 to 22: A detailed ultrasound of the baby's organs, growth and the placenta.
Glucose screening, weeks 24 to 28: A blood test an hour after a sugary drink, to check for gestational diabetes.
Tdap (whooping cough) vaccine, weeks 27 to 36: Recommended in every pregnancy; antibodies pass to the baby. Earlier in this window is best.
Rh immune globulin, week 28: A shot around week 28 if your blood type is Rh negative.
Group B strep test, weeks 36 to 37: A quick swab. If positive, you get antibiotics in labor to protect the baby.
Weekly visits and birth plan, weeks 36 to 40: Visits are usually weekly from 36 weeks: position checks, blood pressure, your plan for labor.
Past your due date, weeks 40 to 41: Extra monitoring, like a non-stress test or a fluid check, and a conversation about induction.

The RSV vaccine is offered between weeks 32 and 36 when that falls between September and January. Every practice runs its own schedule; this is the common US pattern.

Following your own weeks

If you know your due date, CycleHelm can follow along: the week you're in, what's changing for you, what's worth doing that week and what to ask at your next visit. No due date yet? Start with the due date calculator.

The warning signs that mean calling your care team straight away are always free to read in the app: bleeding or leaking fluid, a severe headache or vision changes, fewer movements from 28 weeks, severe belly pain, a fever of 100.4°F or more, or sudden swelling of the face or hands.

Questions people ask

How are pregnancy weeks counted?

From the first day of your last period, not from conception. So 'week 6' means six weeks since that period, about four weeks since conception. '12 weeks, 3 days' means 12 full weeks and 3 days into the 13th.

When does each trimester start?

The first trimester runs to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 to birth.

Are the baby's sizes exact?

No. They're averages, rounded, measured head to bottom until about week 20 and head to heel after. Your scans measure your own baby, and healthy babies vary.

When will I feel the baby move?

Usually between weeks 16 and 22, earlier in a second pregnancy. From about 28 weeks, get to know your baby's usual pattern of movement and call your care team the same day if it slows down or changes.