13 weeks pregnant: the second trimester starts

At 13 weeks pregnant you're in the second trimester, which KKH's planner calls the smoothest of the three for most women. Energy often returns and the early symptoms fade, though some women carry nausea and tiredness into the fifth month. For your baby, the head has done most of the growing until now. From here, the body catches up.

Why there's no exact size this week

In the second trimester babies grow at different rates, KKH says, so it's hard to match an exact measurement to a week. Its planner switches to estimates every four weeks instead. Here are KKH's figures:

KKH's planner doesn't give a figure for week 24. Before week 13, KKH says, the head made up almost half of your baby's crown-rump length; now the rest of the body grows faster.

What you might feel

KKH's planner runs the second trimester from week 13 to week 28; other KKH and NUH pages end it at week 26 or 27. Whichever count your clinic uses, most women feel better in it. You won't be symptom-free, and if you feel very low, KKH asks you to talk to your partner and your doctor.

Is sex safe now?

In an uncomplicated pregnancy, yes, and it won't harm your baby, KKH says. Its pregnancy pages list when to avoid it:

• a low-lying placenta (placenta praevia)
• a leaking or burst water bag
• vaginal bleeding or abnormal discharge
• preterm labour
• genital sores or a sexually transmitted infection in either partner

More blood flows to the pelvis in pregnancy, so light bleeding after sex can happen, and so can brief cramps. If the cramps get stronger or you bleed, see your doctor.

Singapore checks this week

• Last days for first trimester screening: KKH does the scan and blood test up to 13 weeks 6 days.
• KKH's antenatal classes take registrations after 16 weeks, so look at dates now. Our antenatal classes guide compares providers.
• The flu vaccine, if you haven't had it, can be given at any stage of pregnancy.
• Keep your bills for the MediSave Maternity Package, and see our prenatal check-ups and scans guide for what's next.

When to call the hospital

Bleeding after sex with strong cramps, fluid leaking, severe tummy pain, fainting, chest pain or breathlessness need a same-day check.

At KKH, early pregnancy problems such as bleeding and tummy pain go to the Urgent O&G Centre, a 24-hour walk-in centre at Basement 1 of the Women's Tower. For minimal bleeding or mild pain under 16 weeks, KKH's Early Pregnancy Assessment Unit offers appointments the same or next working day. Booked elsewhere? Call that hospital's O&G clinic, or go to its emergency department after hours.

Frequently asked questions

Is 13 weeks the second trimester?

Yes. KKH's planner counts the second trimester from week 13 to week 28; some KKH and NUH pages end it at 26 or 27 weeks.

Is it too late for first trimester screening at 13 weeks?

Not quite. KKH does the scan up to 13 weeks 6 days, so book it this week if you still want it.

How big is my baby at 13 weeks?

Between KKH's figures for 12 weeks (about 5.1cm) and 16 weeks (about 12cm and 146g). KKH gives estimates every four weeks from here because babies grow at different rates.

13 weeks pregnant is how many months?

About three months, counted from the first day of your last period.

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