Second trimester essential guide

Your Essential Pregnancy Guide: Second Trimester (+ Animation)

The second trimester is fabled to be the ‘best’ during pregnancy. Jump in to our guide and learn how you and your baby develop during weeks 14-28 of pregnancy

12 min read

 Pregnancy – Article by 

Although getting halfway through things can sometimes be unsatisfying – like that TV show you’re binge-watching that suddenly disappears – when it comes to pregnancy, it’s really satisfying. The second trimester marks a halfway point in your pregnancy. Not only are you (hopefully) feeling better but you’re closer to meeting your little human.

Our second trimester pregnancy guide gives you an overview of what to expect, a weekly look at what’s happening to you and baby, plus things you need to do and things to look out for.

In a hurry? Watch the animation below for a quick overview or jump to the section you need:

Overview of the second trimester
Weeks 14-17
Weeks 18-20
Weeks 21-24
Weeks 25-27
Things to do in the second trimester
When to seek medical help in the second trimester

You can also look back to our first trimester pregnancy guide or get prepared for the third trimester.

Let’s jump into the second trimester.

Overview of the second trimester

With most of your early pregnancy symptoms gradually disappearing, the second trimester (that’s weeks 14-27) is a bit of a sweet spot. You should get that fabled ‘pregnancy glow’ (it exists), begin to look pregnant (and not just like you’ve overindulged in tacos at lunchtime) and, excitingly, be able to feel your baby move around 20 weeks.

With your increasing waistline, you may find from 20 weeks onwards you need to hang up your usual skinny jeans and stock up on stretchy, looser clothes instead. This is especially true as you might find yourself feeling hungrier and your weight gain may speed up.

If you’ve suffered with morning sickness through your first trimester, it should ease by the second trimester. Although for an unlucky few, you can continue to feel queasy into 20 weeks, and beyond.

While most of the unpleasantness of the first trimester should ease, there are a few new things you may experience, including:

  • Breast changes and some drops of colostrum (the first early milk) present.
  • Aches and pains (low back pain is common).
  • Practice tightenings of your womb (Braxton-Hicks contractions).
  • Bleeding gums.
  • A metallic taste in your mouth.
  • Skin, hair and nail changes.
  • Nose bleeds, a stronger sense of smell, colds and sinus problems.
  • Restless legs and leg cramps.
  • Heartburn.
  • Swelling in legs, feet and hands.
  • Vaginal changes.
  • A renewed interest in sex.
Second trimester essential guide

What’s happens to your baby during the second trimester?

By the beginning of the second trimester, your baby is about the size of half a banana. Their body is covered with soft downy hair and their fingerprints have formed. Throughout the trimester, they’ll grow rapidly with things like fingernails, eyes, eyelashes, eyebrows and genitals all forming.

By the end of the second trimester, their digestive system is working, and their lungs are preparing to breathe. They’ll also be able to hear and respond to voices and will have a sleep-wake pattern going on. Their eyes begin to open and, adorably, they’ll be able to suck their thumb.

Second trimester essential guide

Weeks 14 to 17

What’s happening to you?

As the second trimester starts, you’ll probably find the nausea and vomiting of the first trimester is disappearing, giving you lots more energy. In its place, you might start feeling congested. Thanks to all the blood pumping round your body, your nose can get congested. Because the tiny vessels in your nose are so fragile, you could find yourself having small nose bleeds. Or you may feel like your ears are always blocked.

Another lovely thing you may experience in the second trimester is a heavier than normal vaginal discharge. As long as it’s thin, whitish and not smelly, it’s completely normal. If it’s yellowy, smelly or irritating, chat to your LMC – you may have an infection.

What’s happening to your baby?

By week 14, your baby is 7-10cm long which is roughly the size of half a banana and their fingerprints have formed.

By 15 weeks, they’re 10cm long and covered in soft, downy hair. They’re able to suck, swallow and grip.

By week 16, they’re 11cm long with working joints and limbs and their fingernails have formed. Their nervous and muscular systems are developed enough by now that their facial muscle movements can form a variety of expressions (look out for that at your 20-week scan!). Also, their eyes will have become sensitive to light.

By week 17, they’re 12cm long, putting on weight and using their diaphragm to practice breathing. They’re busy drinking amniotic fluid and emptying their bladder. At an almost hourly rate, this is even more often than you…

Second trimester essential guide

Weeks 18 to 20

What’s happening to you?

By the end of week 20 you’re officially halfway through your pregnancy! Your womb has expanded up and out of your pelvis and the top of it is about level with your belly button.

From 20 weeks on, you should be able to regularly feel your baby’s movements. At first, it’ll only be you that can feel them but within a few weeks, whoever else you invite to touch your belly should feel them too.

The first movements will probably feel like little flutters (similar to the sensation of ‘butterflies’ when you’re nervous). That’s because baby only weighs about 250g and its limbs are about 6cm long (around the size of your little finger). It’ll be a few weeks before these little flutters feel like you’re being booted from the inside by your baby!

Second trimester essential guide

What’s happening to your baby?

By week 18, your baby is 14cm long and they may start sucking their thumb. They’ll be busy moving their arms and legs and kicking.

By 19 weeks, they’ll be 15cm long with a heartbeat that’s much faster than yours. Their genitals will be fully formed too.

By week 20, they’re 16cm long. Their brain nerves are developing, and they’ll have hair on their head. By the end of this week, their skin won’t be quite as transparent as it has been because fat is starting to collect under their skin. The oil glands in their skin are starting to secrete a waxy substance called vernix. Vernix protects their skin from the amniotic fluid and from getting scratched – tiny fingernails and toenails are growing too.

Second trimester essential guide

Weeks 21 to 24

What’s happening to you?

Finally, these are the weeks that you might get that ‘pregnancy glow’ – your pregnancy hormones have kicked in again, making your hair lustrous and your skin glowy. You’re getting big enough to look obviously pregnant (and not just like you’ve had a big lunch) but not so big that you’re uncomfortable. Baby will also be doing a good job of being noticeable with regular movements you can feel.

As your bump is getting bigger, the ligaments that support it are continuing to stretch while your lower spine is curving more to offset the extra weight and front-loading. Combine this with your pregnancy hormones (yep, them again) softening your joints and supporting ligaments, and your body needs to work hard to maintain its balance and centre of gravity. Understandably, you may be experiencing some back pain.

Second trimester essential guide

Growing breasts, as well as a bump

As well as a growing bump, you may find your breasts are growing too. You might have had a growth spurt at the start of your pregnancy, or you might still be waiting – sometimes your breasts won’t grow until near the end of your pregnancy or until the first few days after baby is born.

Whatever’s going on with your breasts, by now you’ll probably have noticed that your nipples and areolae (the darker circle surrounding your nipples) have got darker. Your breasts may also leak some colostrum – baby’s first food which comes in before breastmilk – if you put pressure on them, like when you’re sleeping. 

Hair and skin changes during the second trimester

You might find that you have more hair than usual – hormonal changes in your body slow your hair-losing rate. You also might find that your dry hair has become oily, or your hair is curlier or frizzier than usual. Hair also might be appearing in new places on your body, like your face or abdomen. It’s fine to pluck or wax these little critters away.

Because your skin cells are multiplying madly to cope with the growth of your belly, sometimes the cells near the surface of your skin become hyperactive. If this happens, you might notice little tags of skin, like under your breasts or arms or in the creases of your neck. These will probably disappear on their own after pregnancy. If not, they can be easily frozen off by your doctor. 

(psssst…there’s heaps of information about skin changes during pregnancy over on our page called – guess – an overview of skin changes during pregnancy)

If you’ve got freckles or moles, you might notice them darkening or more of them appearing. Again, they’ll probably fade or disappear once you’ve given birth.

Finally, you’ll begin to notice Linea Nigra – a line of darkly pigmented skin that runs from your belly button to the top of your pubic hair. Once again, it’ll fade after pregnancy.

Second trimester essential guide

What’s happening to your baby?

By week 21, your baby is developing eyebrows and eyelashes. Their digestive system is working, and vernix is covering their skin.

By 22 weeks, they’re 19cm long and can hear voices.

By week 23, they’re 20cm long with fully formed eyes (although they won’t have colour yet) and wrinkled skin.

By week 24, they’re 21cm long and their lungs are getting ready to breathe. They weigh around 600g (which is a little heavier than a pack of butter) and their skin is thicker and less see-through than it has been.

During these weeks, your baby’s senses are developing. Taste buds are forming on their tongue, their brain can process the sensation of touch and their inner ear is developing. This means by the end of week 24, your baby knows when their head is up or down.

Plus, your baby’s reproductive organs are continuing to develop. A boy’s testes are beginning to descend from his abdomen. While a girl’s uterus and ovaries are formed and, amazingly, her ovaries have already produced all the eggs she’ll ever have.

Second trimester essential guide

Weeks 25 to 27

What’s happening to you?

Your womb is now midway between your belly button and your breasts. As your lung capacity continues to increase, you might notice you breathe a little faster and you get out of breath a bit quicker, especially when you’re exercising.

Your pregnancy hormones are continuing to wreak havoc. Now, they’re slowing the movement of food through your digestive slow and the flow of urine from your kidneys to your bladders. Which means you’re more likely to suffer from heartburn, constipation and UTIs (urinary tract infections). An untreated UTI can trigger labour so be sure to contact your LMC straightaway if you think you have one. Look out for pain when you pee, fever and strong-smelling urine.

You might now be aware of Braxton-Hicks contractions. These are practice contractions that are keeping your womb toned for labour. They’re generally painless although they can be uncomfortable – understandable, as your womb is getting tight and hard for up to 20 seconds. You should feel these in your abdomen. If you feel lower pelvic cramping at the same time, call your LMC. It’s also perfectly normal for you not to feel these contractions until much later in your pregnancy, or not at all.

Finding a comfortable sleeping position might be getting trickier. Try a maternity pillow (a super long, comfortable pillow you can cuddle up against) to help support your joints. If you’re a back sleeper, now’s the time to try sleeping on your side. As baby grows and gets heavier, this weight puts pressure on the major vessels leading to and from your heart which can compromise the circulation and supply of oxygenated blood to your placenta.

Second trimester essential guide

What’s happening to your baby?

Your baby is having a growth spurt over these few weeks. Limbs are getting longer and stronger and fat is developing under their skin. Their unique fingerprints and footprints have developed.

By week 25, your baby has a fixed pattern of wake and sleep times and can recognise your voice. They’ll be impressing you with their moves and somersaults when you’re still (or more likely, trying to sleep).

By 26 weeks, they’re 23cm long and still practicing their breathing. They also respond to touch. That’s because their brain and nervous system are quickly growing and developing, including their brain developing those characteristic ‘wrinkles’.

By week 27, they’re 25cm when tucked up and around 38cm when their legs are extended. Their eyes begin to open, and they can be finger- and thumb-sucking. They can now see, hear, smell and taste (they’ll be drinking amniotic fluid).

Your baby’s lungs, liver, immune and digestive systems are still quite immature, but if they’re born now, they’ll have an 80-90% chance of survival if they’re supported by neonatal intensive care.

Second trimester essential guide

Things to do in your second trimester

Alongside the excitement of planning for baby’s arrival, here are the tests and screening you may do during your second trimester.

20-week anatomy scan

Your LMC will offer you a referral for the 18-22-week scan. It checks part of your baby’s body to make sure that they’re growing and healthy. But most people know this scan because it’s when you can find out the sex of your baby – if you want to. Make sure you tell your LMC (and remind the sonographer performing the scan) if you don’t want to know.

Gestational diabetes blood test

Once you’re between 26 and 28 weeks pregnant, gestational diabetes can be spotted. This test involves drinking a high-glucose solution and waiting an hour before having your blood taken. The test ensures that your body can properly deal with sugar during your pregnancy. Your LMC will refer you for this test.

Second trimester essential guide


If you opted for additional testing during your first trimester [Link to first trimester guide and things to do section] and the combined screening results of the blood test and scan put you at high risk of having a baby with a genetic abnormality like Down syndrome, you may have decided to have an amniocentesis to find out more.

An amniocentesis usually happens when you’re 16–18 weeks pregnant. Read more about amniocentesis

Parental leave

Whether you’re employed or self-employed, now’s a good time to apply for parental leave – you need to apply to your employer by the time you’re 24-26 weeks pregnant. Employment New Zealand has all the information you need.

(Expert coach Rebekah Fraser has easy to follow advice on how to discuss your pregnancy and maternity leave with your employer)

Second trimester essential guide

When to seek medical help in your second trimester

Although you may be feeling better than you did in your first trimester, you may still be experiencing some completely normal things, like heartburn, indigestion and backache.

There are some non-normal things to watch out for though – if you experience any of these, ring your LMC straightaway:

  • Severe abdominal pain or cramps.
  • Severe nausea or vomiting.
  • Bleeding.
  • Severe dizziness.
  • Pain or burning during urination.

By the end of week 27, you’re on the home stretch – the second trimester is done and you’re ready to begin the third – and final – trimester. See what’s waiting for you in the third trimester.

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