At 25 weeks the cortex of the baby's brain (the outer layer) is developing into layers in preparation for more sophisticated brain activity like thinking, feeling and planning in the years to come.
Your baby weighs approximately 660g and measures around 35cm from head to heel.
The structures that form the spine start to form this week and the blood vessels in the lungs continue to develop this week. The baby's nostrils are taking shape and may open up by the end of this week. The baby's eyes are now fully functional, and the baby may blink as a reflex reaction to a loud or sudden noise. Studies have shown that an unborn baby will turn it's head if a light is shone onto the mothers abdomen, proving that the optic nerve is now working.
The cortex of your baby's brain is developing into layers, preparing for more sophisticated brain activity like thinking, feeling and planning in later years.
Your uterus is now about the size of a volleyball. As the uterus continues to grow you will notice it places some pressure on your back and pelvis. In some women this cause shooting pains either down the leg or in the lower back. For some women these pains get more and more severe as pregnancy progresses.
A back condition called sciatica can develop during pregnancy. This often happens when the baby's head presses against the pelvic bones. This causes the nerves in the lower back and legs to be compressed. Severe pain often results and can occur in the lower back, leg or legs and even buttocks. Some women will also experience numbness or tingling in the legs.
At around this time you should talk with your midwife to make sure you understand the signs of pre-term labour. There are many warning signs that may indicate your body is going into labour early. Some of the more telling signs include: Continuous cramping in the lower abdomen similar to menstrual cramps. Contractions that come at regular intervals or more than 4 contractions in one hour. Low backache that is constant. Pressure in the pelvis as if your baby were pushing down. Bloody or watery vaginal discharge.
My Experience at 25 weeks
I had an antenatal appointment in week 25. The midwife checked my blood pressure, urine, felt the baby and the position it was lying in and listened to the baby's heart beat which I could hear. It was quite amazing to hear the heart beat. At this stage of my pregnancy I had now seen my baby twice via ultrasound and heard it's little heart beating.