13 weeks pregnant: a third of the way, and a small bump appears

The worst of early pregnancy is often behind you. This week is about small, useful habits: gums, infections, pelvic floor.

Updated October 13, 2026 · sources checked October 13, 2026

In short

At 13 weeks you are about a third of the way through: the NHS guide counts this as the start of the second trimester, ACOG still as the last week of the first. The NHS says your baby is about 7.4 cm and moving more deliberately. The one thing to do this week: start daily pelvic floor exercises, a small habit with a lasting payoff.

Where you are at 13 weeks

You are about a third of the way through, at the start of month four in Cleveland Clinic's grouping. The trimester label depends on the source: the NHS guide counts week 13 as second trimester, while ACOG's first trimester runs to 13 weeks and 6 days. What matters more is how you feel, and the NHS says you are hopefully through the worst of your symptoms. Track your week with the pregnancy week calculator.

Your baby this week

The NHS gives a length of around 7.4 cm and compares your baby to a peach.

The ovaries or testes are fully developed inside, with final changes happening outside (NHS).
Movements are becoming more deliberate, after the random jerks of earlier weeks. You may not feel them until around week 17 or later.
Some babies suck their thumb, which helps develop the sucking reflex needed for feeding.
Cleveland Clinic adds that the vocal cords form and the head starts to grow more in proportion to the body.

Your body: a bump, more blood flow, sore gums

A small bump may show as your womb grows up and out. The need to pee often may ease as the womb moves away from your bladder (NHS).
More blood in the pelvis can raise sex drive for some and make you thirsty: drink plenty.
Gums. Swollen, bleeding gums are common. The NHS suggests a soft toothbrush in gentle circles, rinsing with water after vomiting, alcohol-free mouthwash, and not smoking.
Other common signs now: round ligament pain on the sides of your bump, nosebleeds, bloating, constipation, heartburn, leg cramps, feeling hot, and swollen hands and feet.

Protect yourself from infections

The NHS lists simple steps:

avoid anyone with chickenpox or rubella, and call your midwife or doctor straight away if you think you were exposed
let someone else empty the cat litter tray, because cat faeces can carry toxoplasmosis
avoid undercooked meat, cured meats like salami, and unpasteurised goats' milk and cheese
get advice before travelling to an area affected by Zika

Start your pelvic floor exercises

The NHS suggests starting now: gently squeeze the muscles you would use to stop the flow of pee, then relax. A Cochrane review (Woodley 2020, 46 trials) found that continent pregnant women who did pelvic floor training were probably less likely to report urine leaks in late pregnancy, and slightly less likely 3 to 6 months after birth. A few minutes a day is enough to begin.

Is this normal? When to call

Round ligament twinges and bleeding gums are normal. Call your maternity unit, GP or NHS 111 (UK), or your OB-GYN or midwife (US), for vaginal bleeding, burning or pain when peeing (urine infections are more common now, the NHS notes), a temperature of 38C (100.4F) or above, or contact with chickenpox or rubella. Call 999 or 911 for heavy bleeding with severe pain.

Appointments and tests

UK: if your dating scan has not happened yet, it can still be done up to 14 weeks with the combined test; after 14 weeks you will be offered a different blood test between 14 and 20 weeks (NHS). Your next routine appointment is at 16 weeks.
US: first-trimester screening runs to 13 weeks; if you missed it, ACOG says the quad blood test is done between 15 and 22 weeks.

Your week 13 checklist

Do pelvic floor squeezes daily.
Book a dental check-up; in the UK ask for your maternity exemption certificate (free NHS dental care and prescriptions).
Hand over the cat litter tray.
Think about telling your employer if you have not yet: the NHS notes many people do so after the first scan.
Look at antenatal classes, even if this is not your first baby.

For your partner

Take over the litter tray for good, and do the class research together.

Previous and next week

Week 12: the dating scan · Week 14: colostrum and energy returning · The first trimester · The second trimester · All weeks · Due date calculator

Questions parents ask

Is 13 weeks the first or second trimester?

It depends on the source. The NHS week-by-week guide places week 13 in the second trimester; ACOG defines the first trimester as running to 13 weeks and 6 days, so the second starts at 14 weeks.

Why are my gums bleeding at 13 weeks pregnant?

Swollen, painful and bleeding gums are common in pregnancy, the NHS says. Use a soft toothbrush with gentle circles, rinse with water after being sick, choose an alcohol-free mouthwash and keep up dental check-ups; in the UK, NHS dental care is free during pregnancy and for a year after the birth.

Is sex safe at 13 weeks pregnant?

The NHS says sex during pregnancy is safe unless your midwife or doctor has advised otherwise.

Sources

NHS — Week-by-week guide: week 13 checked October 13, 2026
Cleveland Clinic — Fetal development: week-by-week stages of pregnancy checked October 13, 2026
ACOG — How Your Fetus Grows During Pregnancy (trimester definitions) checked October 13, 2026
NHS — Antenatal (pregnancy) care and appointments checked October 13, 2026
Woodley SJ et al. (2020), Cochrane — Pelvic floor muscle training for preventing and treating incontinence in antenatal and postnatal women (PMID 32378735) checked October 13, 2026

Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.