If you are in week 13 then congratulations! You have now reached the second trimester! If you are just starting your pregnancy journey then you will want to take a look at The stages of Fetal Development for the first trimester. If you are in week 28 or more then you are in the third trimester which I will be writing about soon so please check back in a week or two! For the stages of baby development in pregnancy for week 13 to week 27 then read on. Or you might want to save this page and check back once a week rather than reading it all at once!
Week 13
So in our stages of baby development in pregnancy, for the second trimester, we are starting with week 13. Your baby is now as big as a lemon with his head starting to get in proportion to the rest of his body. Although there are still some ways to go because it is about half the size of his or her complete frame! There are big changes to your babies bones. In particular the skull and long bones are beginning to harden. The intestines have finally moved into their permanent location within your babies body after being developed inside of a cavity within the umbilical cord. There is also urine being produced and released within the amniotic fluid your baby swims in. His or her vocal cords are starting to develop.
Week 14
Your baby is the size of an orange at between 8 to 10 cm approximately. You may or may not have the beginning signs of a bump, bearing in mind that every woman is different. Your baby is starting to grow hair and eyebrows. His or her genitalia are fully formed too although they still may be too small to see on ultrasound. In other changes, you may start to notice your baby becoming a whole lot more mobile and he or she will be standing up straight with a fully developed neck for support.
Week 15
Big developments are happening in regards to your babies size and weight because over the next few weeks he or she will double in size! Right now your baby as big as a pear. The biggest development is to your babies bones as if it was possible to do an X-ray then the skeleton would now be visible. Since his or her skin is so thin developing blood vessels are also visible. There are some minor adjustments in regards to body parts such as the ears and eyes moved into the correct positions, enabling your baby to look more human.
Week 16
Your avocado sized baby has a fully developed circulatory system with a working heart pumping his or her own blood around the body. Although he or she will not open his or her eyes they are still functioning by being sensitive to light and able to move from side to side. Some babies learn to suck their thumbs to comfort themselves and this can develop from inside the womb, beginning at week 16.
Week 17
If you could hold your baby this week then he or she would fit in the palm of your hand at the size of a large onion. Your child has grown so much in fact that he or she is larger than the placenta at this point! As well as growing rapidly in size your little one is beginning to develop body fat now, although he or she will still be quite skinny. Your baby will also be practicing sucking and swallowing to prepare for when he or she is born. Also important to note, that the heart beat is now regular and regulated by the brain, as opposed to spontaneous and irregular like it was before.
Week 18
There is a lot of construction starting within your babies nervous system and this will continue until your babies first birthday. Myelin Sheaths are growing around the nerve cells to add a layer of protection on them. This will also help to speed up the connections between your child’s brain and his or her movements. Your little one is now entirely unique at this week with his or her own set of finger prints. on his or her fingers and toes. An important development this week is that your child has developed the ability to physically hear your voice. This is due to his or her bones in the ear hardening. As well as your voice the baby may hear your heart beat and embarrassingly, also the gurgling of your digestive track! Your baby is the size of a cucumber.
Week 19
You may notice your babies kicks have a bit more power this week and this will continue in the upcoming weeks. Two things are happening this week to enable your little one to have more thrust and power in those kicks. Firstly the legs have grown into proportion with the arms and the cartilage is growing into bone. Secondly the brain is developing more neurons which are sending more messages to the muscles to speed up those responses from your babies body. In other news your babies lungs are developing a part of the airway know as the bronchioles, which are basically a key component to respiration (breathing), carrying oxygen into the lungs and carbon dioxide out. A substance know as the Vernix Caseosa now coats your babies body. The purpose of it is to protect his or her skin from becoming wrinkled within the amniotic fluid. Your baby is as big as a mango.
Week 20
This week your babies genitalia will be large enough to determine the sex on an ultrasound. If you are having a boy then his testicles will start to travel down from the abdomen. They will not reach the scrotum however for another few months because it is still being developed. If you are having a girl then her external genitalia will be fully formed but her vaginal canal is still under construction. Inside her tiny body will be a miniature uterus, with ovaries containing all of the millions of eggs already made. Your baby will be as big as a sweet potato vegetable.
Week 21
If you would like your baby to get a taste for certain foods then be careful what you eat from this week on! He or she will start drinking the amniotic fluid, mostly to practice using his or her digestive system but also to obtain some nutrition and hydration. While the vast majority of nutrition will still come from the umbilical cord and the placenta, nonetheless, your little one will be developing preferences for the types of food you eat! This will affect what he or she likes to eat when you introduce them to solids a lot later on. Speaking of solids your baby will be the size of a really large banana.
Week 22
There are some significant changes this week when it comes to your babies senses. Even though it is dark inside your belly and your baby’s eyes are not open yet, he or she can still visibly perceive light. Try shining a flashlight onto your tummy to see if your little one will move. Your baby is also getting better at processing sounds as his or her ability to hear develops. He or she is getting really good at listening to your voice as well as hearing the sounds from inside your body. What kind of sounds can they hear inside? Your heartbeat, your breathing, as well as (embarrassingly!) your rumbling stomach! Finally the other sense that is developed is touch. Your baby will have a desire to feel everything around them. They will grab the ambilocal cord and touch the uterine wall as well as explore their own body. Wondering about size? Your baby is as big as a papaya.
Week 23
Your little one has reached the size of a large carrot this week. Within the next month he or she will be adding extra padding at an increased rate too and will double in size. This is due to the production of brown fat, which will grow to keep your little prince or princess warm when he or she is born. Keratin production is beginning too. This is a protein which will be added to your babies skin to thicken and strengthen it and it may even help him or her to begin producing hair. Up until this point your baby has had transparent skin that is very thin and through which you can see his or her organs and bones. There will be an increase in hormones this week resulting in “Baby Brain”. Your placenta is increasing production of the hormones estrogen and progesterone at this point to keep you and your baby healthy and strong.
Week 24
Your baby should really be starting to bulk up now. With the accumulating brown fat as well as growing organs and muscle he or she will be the size of an ear of corn. His or her hair is coming in thick and fast this week eyelashes, eyebrows, body hair and head hair. All of these little details matter. However, with no pigmentation evident yet the hair will have no colour, (regardless of ethnicity), it will still be white. Your babies brain wave activity at this stage is equal to that of a newborn. So if you haven’t started talking or singing to your baby already then you may want to start now. As his or her ability to hear and process sounds has increased too. Therefore if you play the same song or read the same story out loud everyday then your little one will remember it after birth.
Week 25
If it hasn’t been evident already to other people that you are pregnant it will become hard to hide as your pregnant belly (though it varies in size for women) will be around the size of a football. Inside that football sized belly is a baby who is as large as an eggplant at one and a half pounds. The next three weeks will be the time when your baby is the most active so get ready for some sleepless nights while your little one is keeping you awake kicking or rolling around. The biggest development this week however is your babies cardiovascular system. Capillaries are starting to form all around the body, under the skin and even within the forming air sacs in your babies lungs. Your little ones nostrils that have been sealed up until this point will open which may lead to your baby having hiccups as he or she starts to practice taking breaths. This can be annoying for you but it is not harmful to your baby.
Week 26
Up until now your babies eyes have been fused shut allowing the retina to develop. This week they will open for the very first time! Your little one will be able to see inside the womb but his or her eye colour is not developed yet. Your pregnancy belly may become itchy this week due to all of the rapid growth but this is normal and nothing to worry about. Try rubbing some cream on it for relief. In other embarrassing news your belly button will grow from an innie to an outie with all of that stretching. Your baby is the size of a spaghetti squash and will soon reach the 2 pound mark in weight.
Week 27
Nearly at the beginning of the third trimester your little one is reaching the 2 pound mark, and is as big as a cabbage, with your belly now the size of a basketball. If you have started talking to your baby then here is some good news… your baby will begin to recognize different voices, the ones he or she hears most often. His or her auditory development is coming along nicely but he or she will have a coating of vernix in the ears muffling sounds. Baby can hear you, and in exciting news you may also be able to hear baby this week. Get your partner to put their ear to your belly and you may hear babies heartbeat. As your babies lungs continue to develop and strengthen, the chances of him or her getting the hiccups increase, and eating spicy food may be a trigger for this.
If you have made it this far then thanks for reading about the stages of baby development in pregnancy for the second trimester. If you are entering your third trimester then remember and check back in a few weeks for more exciting content!
All the best on your journey towards becoming a mother either for the first time, or again. If you ever need a hand then be sure to reach out in the comments or by email. Your feedback is always appreciated.
Kind regards,
Jacqueline
(future mama to be)