You are 16 weeks and 6 days

Your baby is practicing breathing movements, which are vital to develop his chest muscles and help his lungs grow.

162 days until your due date

In the uterus, your baby practices breathing, which also helps his lungs develop. When he breathes in, his diaphragm moves down and his chest wall moves in.

Each "breath" lasts less than a second. At this stage, breathing movements may happen only occasionally, regularly or irregularly.

Your baby may also open his jaw and swallow as he breathes, and a single breath with a big movement of the diaphragm can look like a sigh.

For the chest movements to work, there must be enough amniotic fluid, especially during the critical period of lung development from 16 to 26 weeks. By week 24, your baby will spend about three hours a day practicing breathing, and about eight hours a day in the last eight weeks of pregnancy.

Focus on

Twins: Growth rate

Most twins grow at about the same pace, but from now on some don't. Your babies are almost certainly developing all the right organs at the right time, even if one is smaller. If a scan finds a growth difference, you'll have extra scans to monitor it. Small differences usually aren't a problem, and doctors aren't normally concerned unless the difference is more than 15 percent.

Ask a Doctor

Why am I getting brown patches on my face?

Up to 70 percent of pregnant women notice changes in skin color. Brown patches on the forehead, cheeks, and neck are called chloasma, or the "mask of pregnancy"; darker-skinned women may get lighter patches instead. It's caused by extra melanin, the pigment that colors skin and hair, and gradually fades after the birth.

To minimize it, stay out of the sun as much as possible, use a high-protection sunscreen, and wear a hat outdoors. Cover larger patches with tinted moisturizer or foundation, and smaller ones with concealer.

As a matter of fact

Smoking and breathing practice

When a pregnant woman smokes, her baby practices breathing movements less.

A British Medical Journal study found that the time the baby spent practicing breathing dropped within five minutes of the mother starting a cigarette.

This is general information based on NHS guidance, not medical advice, and every pregnancy is different. Talk to your midwife or GP about anything that worries you. If your baby's movements slow down or change, or you have bleeding, severe pain or leaking fluid, call your maternity unit straight away. In an emergency, call 999.