TEN GROWTH MILESTONES AT THIRTEEN TO SIXTEEN WEEKS By the end of the 16th week, you can easily feel your grapefruit-sized uterus midway between your pubic bone and your navel. Let's look at 10 growth milestones during this month:
Your little "peach" is about the size of a peach! Baby doubles her length and nearly quadruples her weight. She is around five inches long and weighs around four ounces at the end of the 16th week.
Her arms lengthen this month and she can flex her arms, clasp her hands, and suck her thumb. Her legs lengthen, and kicking intensifies (you probably don't feel it yet).
Her bones (arms, hands, and legs) form and are visible on x-ray or ultrasound. Baby "breathes" amniotic fluid in and out through the developing air passages and tiny sacs in her lungs. Her external ear folds are becoming more developed, as is her hearing, enabling her to react to sounds. She develops her own unique fingerprints. Blood vessels proliferate at a rapid rate and show through baby's thin, still transparent skin.
The placenta becomes the prime producer of pregnancy hormones you will continually need to nourish your baby and yourself, and your baby now free floats in her own bubble of amniotic fluid, contained in an amniotic sac. By the 16th week, there is enough amniotic fluid for doctors to safely enter the fluid- filled sac by a procedure called amniocentesis.
TEN GROWTH MILESTONES AT SEVENTEEN TO TWENTY WEEKS By the end of this month you can feel your cantaloupe-sized uterus at the level of your navel. Other growth milestones include:
Your baby weighs around three-quarters of a pound, and measures between 8-10 inches long. This is about half the length baby will be at birth. Baby's legs, now around the size of your little finger, continue growing, become more muscular, and make their presence felt as tiny flutter kicks.
He waves his growing, but still tiny, arms. On ultrasound, you may see him sucking his thumb and making a fist. Baby hair is beginning to appear on his upper lid, eyebrows, and head. His skin, previously thin and transparent, now begins to accumulate fat deposits. Baby's oil glands start to secrete a waxy substance that mixes with his dead skin cells to form a cheesy coating, called the Vernix caseosa, which acts like a sort of wetsuit protecting the little swimmer's skin from chapping.
Fine, temporary hair—called lanugo (meaning "wool")—covers most of his body and helps to hold the vernix on the skin. Baby's digestive system functions better now, and he regularly swallows amniotic fluid and urinates into it. By this month, baby's middle ear structures have formed, enabling baby to hear sound. Still, baby cannot yet survive outside the womb at this stage because his lungs are still undeveloped.