During this entire week, the baby grows rapidly, with growth setting the stage for development later this month. Your baby’s weight will increase six times during this fourth month of pregnancy. Even then, the baby will only weigh 170g, about as much as an average banana.
Your baby is also adding to its list of reflex behaviors. Reflexes are the automatic, unlearned behaviors a baby is born with. Most reflexes have survival value for the infant: blinking helps keep foreign objects out of their eyes and keeps their eyes moist; sucking and swallowing are for baby to drink milk. Right now, your baby is practicing all three of these reflex behaviors. It is also working on incorporating some additional reflexes, so that by the time it is born, the average full-term baby will display more than seventy different reflex behaviors.
This is a week of rapid, whole-body growth for your baby. Existing bodily structures became larger and more well-developed, but no new structures were formed.
As your baby grows larger and stronger, it becomes more and more likely that you’ll actually begin to feel it move. The very earliest movements are reported around this time during the pregnancy.
You probably still feel tired and sometimes out of energy. That’s normal. Plenty of rest, good nutrition, and exercise should make you feel better. Exercise doesn’t have to include a full workout; 5-10 minutes of walking, stretching, pregnancy yoga, or other activity can be renewing.
Change position slowly, especially if you are getting up from lying down, to avoid feeling faint or dizzy. During pregnancy, blood pressure changes that equalize pressure from changing positions occur more slowly.
The chances are good that you’ve noticed an increase in your appetite. Eating nutritious food provides fuel to sustain the baby’s growth and to give you the energy you need to manage the 'non-pregnant' aspects of your life.