18 weeks pregnant: baby is the size of a bell pepper

Your baby this week

The structures of the ear are now in place, and your baby can begin to hear. The first sounds are muffled, like hearing from under water, and include your heartbeat, your breathing, your digestion and your voice. Sounds from outside may reach your baby, but they are softened by your body and the fluid.

Nerves are developing a protective coating called myelin, which helps signals travel faster. Your baby's eyes are shut but can sense a bright light through the eyelids. If you are having a girl, her uterus and fallopian tubes have formed. If you are having a boy, his genitals are visible on an ultrasound, and your anatomy scan may show this.

How it happens. Sound waves travel through your abdominal wall and the amniotic fluid to your baby's inner ear. Over the coming weeks, the brain regions that process sound develop, and your baby begins to respond, for example by moving when there is a sudden loud noise.

Your body this week

Your uterus has reached about the level of your belly button. Your blood volume has increased a great deal, and your blood pressure tends to be lower in the second trimester than before pregnancy. This is because the hormone progesterone relaxes blood vessels.

At the same time, your skin is responding to hormones that stimulate pigment-making cells, and these can leave marks that were not there before.

Can your baby hear you?

The parts of the ear are formed by about now, and sensitivity to sound develops gradually. Researchers describe a range: many sources say babies begin to detect sound from about 18 weeks, and clear reactions to loud sounds are often reported from around 24 to 25 weeks. By the third trimester, babies respond to voices and music, and studies suggest newborns recognize their mother's voice.

There is no need to do anything special, but talking, singing or reading aloud can be a way to connect. Partners and siblings can join in. Keep music at a comfortable volume, and do not place headphones or speakers on your belly, since loud or sustained sound is not necessary and could be uncomfortable for your baby.

Dizziness: why it happens and what helps

In the second trimester, blood pressure often dips because progesterone relaxes blood vessels. Your growing uterus can also press on the large veins in your abdomen when you lie flat, which lowers blood flow to your heart.

What helps:

• Stand up slowly. Sit on the edge of the bed for a moment before you rise.
• Eat regularly. Do not go for long periods without food.
• Drink water through the day. Dehydration makes dizziness worse.
• Avoid standing still for long. Shift your weight, or sit when you can.
• Avoid overheating. Take care in hot baths, crowded rooms and warm weather.
• Lie on your side rather than your back. This takes the weight off the large veins.

If you feel faint, sit or lie on your side until it passes.

Call your provider if dizziness comes with chest pain, a racing or irregular heartbeat, severe headache, blurred vision, or you faint. Tell them too if dizziness is frequent, since it can also be linked to anemia.

The dark line and skin patches

Increased hormones stimulate the cells that make pigment, and this can darken areas of skin. The linea nigra, a dark vertical line from the navel to the pubic bone, is common, and so are darker nipples and freckles. Melasma is patchy darkening on the face.

These changes are harmless and usually fade in the months after birth. You cannot prevent them, but you can limit melasma by using a broad-spectrum sunscreen every day, wearing a hat and avoiding midday sun. Ask your provider or pharmacist before using any skin-lightening product, since some ingredients are not recommended in pregnancy.