At week 23, your baby is about 8 inches long from head to bottom and weighs slightly over a pound at this point. While the first trimester might have felt like much ado about nothing when it came to the baby's overall size, the second trimester marks a period of rapid growth and development. Baby should almost double her weight over the next four weeks, and while her skin is a bit saggy now, it will soon look full as fat deposits, and increased muscle mass fill the void.
Your baby is now doing some pretty cool internal growing now that her basic structure is there. Her milk teeth are forming inside her gums, she can now sense movement and may enjoy it when you sway to the music, and she is beginning to acclimate to the sounds of the outside world. You might even be able to see her little body squirm depending on your body weight and position. Loud noises like honking horns and movie actions scenes are also being filed away as normal, and she is less likely to startle outside the womb in response to the kinds of noises she frequently hears on the inside. And speaking of hearing, while you have been able to hear baby's heartbeat on Doppler for a long time, it is now strong enough to be heard with a stethoscope or at home listening devices.
Baby's body has a fine downy layer of lanugo hair and vernix for temperature regulation. While the baby is starting to put on a little fat, including brown fat that is deposited around the internal organs and helps stabilize internal body temperature, the vernix and lanugo will help keep her warm in the meantime.
At this point, your baby has around a 30% chance of survival if she is born now. The official term is viability, and this survival rate is based on fetal development and weight, which can vary from baby to baby. Of course, the goal is to keep baby safely inside as long as possible, but it is important to understand the risks should the unthinkable happen, and the baby is born early.
- American Pregnancy Association - Week 23
- WebMD - Week 23