During pregnancy your baby can use up to a third of your body's iron supply, if you do not replace this iron supply with iron rich food such as red meat, poultry, fish, lentils, spinach, dried fruit and iron-fortified cereals then you could end up with anaemia.
Your baby weighs approximately 360 grams. The eyebrows and eyelids are fully developed and the fingernails cover the fingertips.
The baby now opens and closes it's mouth regularly and drinks the amniotic fluid. The waste products are passed back through the umbilical cord and into the mother's bloodstream for her kidneys to dispose of.
The baby's lungs are still developing but are not developed enough for her to survive outside the womb. When the baby inhales, her lungs will fill with amniotic fluid, this helps her to develop the air sacs she will need to breathe after birth.
Your baby already has a high number of red blood cells and the white blood cells are beginning to be produced. Taste buds are also being formed on your baby's tongue at around this time.
As you get bigger try to sleep on your side. Lying on your back means that your uterus presses on major blood vessels, which could make you feel faint and nauseous. If you can sleep on your left side as the pregnancy progresses this will help encourage your baby into the best position for birth.
Your weight gain will be around 10 to 15 pounds by now.
While you're pregnant, your baby uses up to a third of your body's iron stores to make red blood cells, so you need to consume plenty of iron-rich foods to replenish your stocks.
If tests have revealed that you are anaemic (symptoms include exhaustion and dizziness), you may be prescribed iron supplements. A side effect of these supplements is that they can cause constipation. Taking iron supplements can inhibit your absorption of zinc, a mineral that is essential to your baby's development. To boost your zinc levels try eating more red meat, pulses, whole grains and bananas.
My Experience at 21 weeks
I suffered from slight anaemia during both my pregnancies and found myself pretty exhausted. I took iron tablets but did not suffer from the side effect of constipation. Anaemia is detected from a blood test, if the midwife suspects that you are anaemic then they will do a routine blood test.