3rd Trimester: Grow Baby Grow!
Weeks 28-30Healthy babies born around this time have a 90% chance of survival without life-long effects. Baby can open his eyes, but it is too dark to see much inside the womb. He can differentiate between the brightness and the dark. He can hear you and recognize different sounds and voices. He is starting to store fat on his little body. All of his bones have formed, but they are still quite soft. With bone development comes bone marrow and red blood cell production. (The liver was producing red blood cells prior to this point.) He is practicing the grabbing motion by opening and closing his hands and sucking his thumb. His kicks and punches are quite strong and can take Mom’s breath away! The immature respiratory system produces surfactant, which helps the lungs fill with air. The nervous system is still developing but can control some body functions at this point of development. He may weigh in around 3lbs now.
Weeks 31-34His lungs are not yet fully developed, and need more time before they breath ‘outside’ air, but there are rhythmic breathing movements taking place as he practices for coming earthside. The lanugo hair is starting to disappear and the skin is becoming more pink and less opaque. Some babies hold on to their peach-fuzz hair until a few weeks after birth, so don’t be alarmed if your baby has hairy ears! Your baby will be descending into birthing position, hopefully head down! His eyesight is becoming more developed. Iron and calcium are being stored, along with fat. All the fat that is being stored is helping with brain growth, as well as body fat growth.
Weeks 35-38Your baby’s nervous system can now control his body temperature. His movements are felt as he stretches and rolls, but remains low in the pelvis and engaged for birth. His lungs are still ‘practicing’ and are not yet completely ready. Once they are fully mature (generally between 38-40 weeks, but there are always exceptions), a chemical is released that alters the mother’s hormones. Small breast buds are forming. They will feel hard to the touch and be located under his nipples, but will soften during the first few weeks of life. Your little baby is packing on the pounds now. He will gain an average of ½ pound a week from now until birth. He is getting antibodies from you that will help protect him from illnesses after birth. At 37 weeks, he is considered ‘Early-Term.’ This means that if he decides to come on his own, everything should be just fine, but he is not yet at ‘Full-Term.’
Weeks 39-42Your baby has made it to ‘Full Term.’ Your baby’s movements lessen as the womb is becoming crowded and labor is around the corner, but kick counts can still be done to keep Mom calm. His head may be rapidly growing hair (or he could be a bald baby!). His nails are all growing, and will probably need clipped soon after birth. The vernix that once covered him, thick and white, is falling off in the womb. The longer he bakes, the less you will see on his skin at birth. (Don’t forget to rub that natural lotion into baby’s skin!) Your baby’s brain is soaking up the healthy fats and so is his body. The bones to the skull are still soft. They will remain soft so they can mold and move for the birth process to take place. He will weigh between 6-9lbs on average at birth, depending on when birth occurs, with the average length being 19-21 inches. Birth will happen when baby is ready, but typically occurs within this window of time.
Enjoy the last trimester, soon you will be holding your baby!References: https://www.nlm.nih.gov/medlineplus/ency/article/002398.htm http://americanpregnancy.org/while-pregnant/third-trimester/ http://www.hopkinsmedicine.org/healthlibrary/conditions/pregnancy_and_childbirth/the_third_trimester_85,P01242/ http://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/fetal-development/art-20045997?pg=2