13 weeks pregnant
At 13 weeks you are in the first trimester, and your baby measures about 7.4 cm from crown to rump and weighs about 23 g, roughly the length of a pea pod. The last week of the first trimester closes the 12-week scan window on 13+6, and your hospital booking-in visit should be done or booked.
Weighs about 23 g, like a AA battery. Averages from standard growth tables; your scan gives your baby's own numbers.
Your baby at 13 weeks
Vocal cords and fingerprints are forming. The body is catching up with the head, the face looks human and movements are becoming coordinated.
How you might feel
Nausea has usually eased, appetite returns and you may notice a faint dark line down your belly or darker patches on your skin.
Last week of the first trimester. Energy usually returns soon.
Call your maternity unit or GP today for bleeding, severe pain, or if you cannot keep fluids down. 13 HEALTH (13 43 25 84) in Queensland; 000 in an emergency.
What's due this week in Australia
Dating ultrasound
Confirms how many weeks, the heartbeat and whether there is more than one baby.
NIPT blood test (optional, private cost)
A blood test from 10 weeks that screens the baby’s DNA for Down syndrome (trisomy 21), trisomy 18 and 13, and can tell the sex.
12-week scan and combined first-trimester screening
Nuchal translucency ultrasound between 11+0 and 13+6 weeks, with a blood test (PAPP-A and free β-hCG) usually drawn from 10 weeks.
Hospital booking-in visit
Usually at 12–16 weeks, about an hour with a midwife.
Tell your employer (when you are ready)
There is no legal deadline to tell your employer, but protections start once they know: transfer to a safe job, no-safe-job leave and special maternity leave.
Coming up: 16-week antenatal visit
Review of the first-trimester results, blood pressure, the baby’s heartbeat and a referral for the morphology scan.
Checklist for the week
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Questions about 13 weeks
How many months is 13 weeks pregnant?
About three months.
What trimester is 13 weeks?
Week 13 is in the first trimester. In the Australian guidelines Hello Bub follows, the first trimester runs to 13 weeks, the second from 14 to 27 and the third from 28 weeks.
What happens at the hospital booking-in visit?
A longer appointment with a midwife between 10 and 16 weeks: a full history, your model of care, blood pressure, weight, the results of your booking bloods and the plan of visits for the rest of the pregnancy.
Written by the Hello Bub team; medical schedule follows the Australian Pregnancy Care Guidelines; last reviewed 3 November 2026.