Your baby’s skeleton is changing from soft cartilage to bone, and the umbilical cord — her lifeline to the placenta — is growing stronger and thicker. Your baby weighs 5 ounces now (about as much as a turnip), and she’s around 5 inches long from head to bottom. She can move her joints, and her sweat glands are starting to develop.
Baby’s skeleton is hardening, changing from rubbery cartilage to bone, and fat is finally accumulating around it. His umbilical cord is getting thicker and stronger, and those little fingers and toes now feature one-of-a-kind prints.
Your baby’s main job this week is to plump out. She’s now about the right size to fit into your palm, and is developing a layer of fat under her skin. This will help keep her warm after the birth, but for now, your amniotic fluid does the job for her, keeping her at a constant 99.6 degrees Fahrenheit (37.5 Celsius), slightly warmer than your own body temperature.
Your baby is now recognizably either a boy or a girl, with a visible penis and testes or a fledgling uterus and vagina. If you’re having a girl, she already has around two million eggs in her ovaries. Connections are constantly forming in her brain, meaning she has more control over her limbs, fingers and toes. Her blood circulation is well established, and the umbilical cord is becoming thicker and longer to transport oxygen and nutrients into her body. Your baby and the placenta are almost the same size.
You are 17 weeks pregnant. (fetal age 15 weeks)
- The umbilical cord is growing thicker and stronger.
- Fetus weight is just over 5 ounces (150g).
- Baby is about 5 inches (14cm) long crown to rump.
- and would be about 9 inches (23cm) head to toe, if it could stretch out.
- The retina has become sensitive to light.
- The first stools (meconium) are now beginning to accumulate.
They recycle the amniotic fluid by swallowing up to a litre a day. Meconium (composed of products of cell loss, digestive secretion and swallowed amniotic fluid), is accumulating in the bowel. Fat stores begin to develop under your baby’s skin this week. The fat will provide energy and help keep your baby warm after birth.
Baby’s eyes are looking forward now, but they are still firmly closed. The skeleton is tranforming from cartilage to bone. The bones remain flexible to make the journey through the birth canal easier. You can feel your uterus just below your bellybutton. If you put your fingers sideways and measure, it is about two finger-widths (1 inch) below your bellybutton. Your uterus is the size of a cantaloupe.
The crown to rump length of your growing baby is 5 to 5.6 inches (12.5 to 14cm) by this week. Weight of the fetus is about 5.25 ounces (150g).