2nd trimester
You've reached the second quarter and things continue to move forward. Your future child is growing and developing day by day and slowly becoming the little person that will be by your side. Learn how your baby develops week by week and enjoy this present God has given to you.
Week 15
The fetus never stops growing: It measures 10cm in length and weighs 78g. Its skin is covered in a downy hair called lanugo, which will continue to grow until Week 26. Also, you can now know whether it is a boy or a girl, provided that your gynecologist is able to see its genitalia via the ultrasound scanner, which at this stage is not that easy, as it all depends on whether the baby is in the appropriate position.
Week 16
Even though its skin is still transparent, your baby is now completely formed. All that is left now is for its organs to mature and grow. With a length of 12cm and a weight of 110g, its legs have grown to almost the length of its arms. You might feel the fetus moving from time to time. These are what is known as "active movements" of the fetus.
Week 17
By this time a creamy white substance covers the skin and the lanugo. It is what is known as vernix, a substance that protects him from the liquid in which he is floating and will be there for the rest of his stay in the womb. Its quantity will decrease as time goes by. At the same time your baby will begin to build fat underneath his skin (brown fat), which will act as reserves to generate heat on birth.
As to his senses, he is able to perceive intense light through his eyes. By this time your baby measures close to 13cm from head to buttocks (17cm with legs outstretched) and weighs 155g. He is as big in size as the placenta and his heart pumps 25 liters of blood a day.
Week 18
Your baby almost looks like a little person. He measures 14cm, weighs 200g and yawns, makes expressions with his face and can even have a hiccough. He also begins to kick gently, but his kicks are cushioned by the amniotic fluid and the thickness of the womb, so you might not feel them yet. If it is a boy, at this stage the prostate starts to develop.
Week 19
The baby's length is now 15cm and his weight of 260g and his growth rate has started to slow down. Perfectly protected by the amniotic fluid, the lanugo, and the vernix, the priority at this time is the maturation of the organs.
Week 20
Now his length is 17cm and his weight 320g. Growth seems to never stop! Each day that goes by he moves more frequently and with more energy. This is how he learns how to coordinate and develop his muscles. Inside you he postures and gestures: He opens his mouth, yawns, makes gestures, sucks his thumb, and plays with the umbilical cord. In addition, he now swallows amniotic fluid and passes it out as urine, which mixes with the amniotic fluid.
Week 21
Your baby moves an average of 50 times per hour, and this stimulates his physical and mental development, although you might only feel some the stronger movements. If you lie down and eat something sweet it will become easier for you to feel him. What about his measurements during this week? They stand now at 17.5cm in length from head to buttocks, 22cm from head to heels, and 390g in weight.
Week 22
Your baby now measures 19cm in length and weighs 450g. His eyelids and eyelashes are formed and it is now when his brain starts growing and developing spectacularly. If it is a boy, his testes will have started to drop from the pelvis to the scrotum.
Week 23
With a length of 20cm from head to buttocks and a weight of 545g, the baby's arms and legs are now more proportional. At the same time the nervous system develops at an amazing speed. Everything is moving forward at full speed.
Week 24
With a length of 21cm and a weight of 630g, the lungs are developed, although they are still to mature, as is the case with other organs. This is why from this week onwards his capacity to survive outside the womb is higher. He can survive in an incubator with only minor complications.
Week 25
With a length of 22cm and a weight of 725g, during this week the baby's development centers on the lung's blood vessels, the spinal cord structure, this has 33 rings, 150 joints, and 1000 ligaments, and the opening of the nostrils.
Week 26
He now is 23cm long and weighs 820g. The baby's visual system has matured — he is now able to open his eyes — as well as his auditory system — he is now able to hear you and external sounds. For this reason it is a good moment to start establishing communication using your voice. Even if he cannot understand the words, he will be able to recognise your voice and pick up on your emotional state, all of which will strengthen your bond. He might also feel caressed when you stroke your tummy. Continue enjoying it!
By this time his lungs will have started to secrete surfactants with which to cover the inner walls and allow them to expand when breathing.
Week 27
The baby's evolution during this week: 24cm in length, a weight of 910 grams, and all his major systems can now function, although they may have still not fully matured, especially the lungs, which will be the last to complete their development.
Week 28
With a weight of 1 kg and a length of 25cm from head to buttocks, or 35cm from head to feet, your baby is like a little doll with eyelashes, eyebrows, and hair. Thanks to his senses, he is able to recognise your voice and may even be able to retain in his memory the songs you sing to him at this time and recall them when he is born. Don't hold back!
Week 29
Congratulations! Your baby already measures 26cm from head to buttocks and 37cm from head to feet. His weight is around 1.15kg and his head and torso are now in proportion. He grows so fast that if he were to be born right now, he would have a high probability of surviving without adverse consequences.