Week 27 is the beginning of the third trimester. At week 27 the baby is over 2 pounds and 12-13 inches in length. You may notice a big change in length between week 26 and week 27. This is because in the third trimester we measure length as total length of the baby while before the third trimester length is measured as “crown-rump-length” the distance from the top of the head to the baby’s bottom.
Babies born at week 27 usually do well. There is a 90% chance of survival and only about 10% of the babes that survive have significant disability. It is still much better to not deliver at 27 weeks and if you develop preterm labor we will do everything we can to stop the labor and keep you pregnant. If you do deliver at 27 weeks there is an excellent chance of a favorable outcome for the baby.
The third and final trimester starts at week 27. The third trimester can be harder for most women then the second trimester. The changes are gradual but most women will have less energy and more aches and pains. As the baby gets bigger the center of gravity changes in your body. Activities that where once pleasurable can become harder and difficult. The trade off is in knowing that your baby will be here soon.
Week 27 is when we like to do the glucose tolerance test also called the one hour GTT or the O’Sullivan test. This should be done between 26 and 28 weeks. This is a test for gestational diabetes, diabetes of pregnancy. The test involves drinking a measured amount of glucose and checking the blood sugar one hour latter. The idea is to see how your body handles this sugar load to be sure the body is processing sugars appropriately. Although classically this test is not done fasting, most obstetricians will want you to fast before the test. This is for two reasons, it allows a fasting blood sugar to be taken before the test and gives fewer false positive results. If the one hour GTT is abnormal, a 3 hour GTT will likely be ordered. This is a similar test except twice as much of the sweet drink is given and blood sugars are checked every hour for 3 hours. These are pretty obnoxious tests but the information is extremely important. If gestational diabetes is diagnosed and treated, everything should be fine. If gestational diabetes is present but not found, it can lead to pregnancy disasters.
At week 27 the baby can distinguish between different voices. It is important to talk to your baby. The baby will recognize your voice when it is born and that will be comforting for the baby. This can also bring great joy to the baby’s mom and dad as the baby reacts inside the womb to the parent’s voices.