Pregnancy Week 15: Staying Active and Your Baby's Senses Developing

8 min read

Quick answer: At week 15 your baby is about the size of an apple, roughly 10cm crown to rump, with eyes sensitive to light and taste buds forming. Your bump is showing and you may feel better than in the first trimester. The NHS recommends at least 150 minutes of moderate activity a week, plus daily pelvic floor exercises.

What parents need to know

Week 15 finds many mums-to-be in one of the most enjoyable phases of pregnancy. The worst of the first trimester is behind you, the bump is showing, and your baby is developing. This week we look at staying active during pregnancy and the development of your baby's senses.

Size	About the size of an apple
Length	Around 10cm crown to rump
Exercise target	150 minutes of moderate activity per week
Pelvic floor	Three sets of exercises daily

How big is your baby at 15 weeks?

Your baby is now about the size of an apple, around 10cm from crown to rump. They're putting on weight steadily, though they're still quite lean at this stage.

What's happening with your baby?

Your baby's senses are beginning to develop this week. Their eyes, while still sealed shut, are sensitive to light. If you were to shine a torch near your bump, your baby would likely move away from it. Taste buds are forming on your baby's tongue, and they're already tasting the amniotic fluid, which is flavoured by whatever you eat. Research suggests that babies exposed to a wide variety of flavours in the womb may be more receptive to different foods after birth.

Your baby's bones continue to harden and ossify. The skeleton is becoming stronger by the day, supported by the calcium in your diet. The skin, while still very thin and transparent, is developing layers. Lanugo (the fine body hair) continues to grow. Your baby's legs are now longer than their arms, and all four limbs are moving actively in the amniotic fluid.

Close-up of a baby's hand grasping an adult's finger, symbolizing trust and love.

What's happening in your body?

At week 15, you're likely feeling noticeably better than you did in the first trimester. Your uterus continues to rise out of the pelvis, and you may be able to feel a firm, rounded shape just below your navel when you press gently. Your bump is properly showing now. You may find that strangers are starting to notice.

Nosebleeds and nasal congestion are common in the second trimester due to increased blood flow and the effect of hormones on the nasal membranes. This is harmless, though it can be uncomfortable. Keep well hydrated, use a humidifier if nasal dryness is a problem, and see a GP if you have regular nosebleeds. Go to A&E if a nosebleed lasts longer than 10 to 15 minutes, the bleeding seems excessive, you're swallowing a large amount of blood that makes you vomit, the bleeding started after a blow to your head, you feel weak or dizzy, or you're having difficulty breathing. Do not drive yourself to A&E: ask someone to drive you, or call 999 and ask for an ambulance.

Round ligament pain — a sharp, stabbing or stretching sensation in the lower abdomen or groin — may become more noticeable as your bump grows. This is caused by the ligaments that support the uterus stretching under pressure. It typically eases with rest. Call your maternity unit immediately (or NHS 111 if it is not available) if the pain is severe or does not go away after you've rested for 30 to 60 minutes, or if you have tummy pain with vaginal bleeding or spotting, regular cramping or tightenings, lower back pain, vaginal discharge that's unusual for you or fluid leaking from your vagina, pain when you pee or needing to pee suddenly or more often than usual, or pee that looks cloudy, pink, red or brown. If you're less than 20 weeks pregnant, you may need to contact your GP or an early pregnancy unit instead, depending on what's available in your area. Pelvic girdle pain (PGP), a common pregnancy complaint, can also begin around this time. If you experience significant pain in the pelvis, hips, or lower back, speak to your midwife for a referral to a physiotherapist.

Exercise in the second trimester

The second trimester is an excellent time to establish or maintain a regular exercise routine. The NHS recommends at least 150 minutes of moderate activity per week for pregnant women, spread over several days. Moderate activity means you can hold a conversation but are slightly breathless.

Excellent pregnancy-safe exercise options include walking, swimming (gentle swimming or aquanatal classes are particularly good for pregnancy as the water supports your bump), pregnancy yoga or Pilates (which also helps prepare your body for labour), cycling on a stationary bike, and low-impact aerobics classes specifically designed for pregnancy. Avoid contact sports, activities with a high risk of falling (such as horse riding or skiing), and high-impact running if it causes discomfort. Do not go scuba diving while you're pregnant, because your baby has no protection against decompression sickness and gas embolism (gas bubbles in the bloodstream). Do not lie flat on your back for long periods, particularly after 16 weeks, because the weight of your bump presses on the main blood vessel bringing blood back to your heart, and this can make you feel faint.

If you haven't been exercising before pregnancy, now is the time to start gently. Begin with short walks or a gentle pregnancy yoga DVD, and gradually increase the duration and intensity as you feel comfortable.

Pelvic floor exercises

It's never too early to start pelvic floor exercises. The pelvic floor muscles support the uterus, bladder, and bowel, and they undergo significant strain during pregnancy and childbirth. Regular pelvic floor exercises throughout pregnancy and after birth significantly reduce the risk of urinary incontinence and support recovery. Aim to do three sets of exercises daily, holding and releasing the pelvic floor muscles. Your midwife or a physiotherapist can guide you on technique if you're unsure.

When to get help

Some symptoms in pregnancy can be a sign of something serious and need checking quickly. This is who to contact, and how soon.

Call 999 if:

you're bleeding from your vagina and the bleeding is heavy (soaking a period pad soon after putting it on), or you also have severe pain in your tummy, pain in your shoulder, or feel sick, faint, dizzy or lose consciousness
you have severe difficulty breathing (you're gasping, choking or not able to get words out) or your chest feels tight or heavy
you have pain and swelling in one leg and you also feel short of breath or have chest pain. A blood clot in the leg can travel to your lungs, which can be life-threatening
you have possible signs of sepsis, such as breathing very fast, being confused or having slurred speech, blue, pale or blotchy skin, a rash that does not fade when you press it, or a very high or very low temperature. Being pregnant makes sepsis more likely
you do not feel you can keep yourself safe (a mental health emergency is as serious as a physical one)

Always call 999 if you think it's a life-threatening emergency, no matter what stage of pregnancy you are.

Call your midwife, maternity unit or early pregnancy unit now if:

you have light bleeding or spotting, even if you have no pain or only mild tummy pain
you have stomach pain that is severe or does not go away after you've rested for 30 to 60 minutes, or stomach pain with regular cramping or tightenings, lower back pain, or pain when you pee
you have a gush or trickle of fluid from your vagina, which could be your waters breaking, or vaginal discharge that's unusual for you
your skin is very itchy (for example, it keeps you awake at night), the palms of your hands or soles of your feet are itchy, or the itching is worse at night. This can be a sign of a liver condition called intrahepatic cholestasis of pregnancy (ICP) that needs urgent treatment
your breathlessness comes on suddenly, you're out of breath when you're lying down, or you're breathless and also have chest pain or feel dizzy
you have pain or swelling in one leg, usually in the calf or thigh. This could be a blood clot (deep vein thrombosis, or DVT), which is more likely when you're pregnant
you have a high temperature (38C or above), or you feel hotter than usual or shivery. A high temperature can be a sign of an infection, so it's important to get it checked

If you cannot reach them, or you're not sure what to do, call NHS 111.

Speak to your midwife or GP if:

you're worried about your mental health, or stress, anxiety or low mood are affecting your day-to-day life. If you need urgent help for your mental health, call 111 and select the mental health option, or ask for an urgent GP appointment

Your week 15 checklist

This week:

This week

Aim for 150 minutes of moderate exercise per week.
Start daily pelvic floor exercises.
Eat a calcium-rich diet to support your baby's bone development.
Mention any pelvic pain to your midwife.
Enjoy the food you're eating knowing your baby can already taste it.

Sources: NHS, Tommy's, NCT. General information, not medical advice.

Sources & further reading

General information, not individual medical advice. Speak to your GP, midwife or health visitor about your baby’s needs.