Baby, Baby Growth and Support

12-week push: Here’s how your baby is developing

12-week push: Here's how your baby is developing

Developmental spurts in your baby are especially important, because little by little your offspring is getting used to the world. Look forward to the next few weeks and see what new things your baby discovers from the third month. What challenges await you and your baby. Here you get all the important information.

Baby 12 weeks: growth spurt

The 12-week spurt is the third growth spurt of a total of eight major developmental spurts in the first year of life. In this phase, your baby makes an important developmental leap. This leap in development is very demanding on your offspring’s brain. It develops social behavior and begins to interact more with you. For example, if you smile at it, your baby will beam back.

Your baby will become curious and the world around you will be much more interesting. Your baby’s world is changing. It’s starting to get more and more independent.

Your baby tries out new things and learns to deal with your own body. Be it examining the top and bottom of the hands, observing the movement of the feet or studying a face, eyes, mouth and hair.

Remember, every child develops at their own pace. Your baby doesn’t have to be able to do everything right away. So don’t put yourself under any pressure when it comes to your baby’s developmental order. Here you can find out how music can have a positive effect on the development of the child.

Growth spurt: what are the signs?

As your baby’s new skills change the familiar world, the growth spurt will make your baby more restless and clingy. It will seek closeness with you and wants to be carried a lot. Mostly it is nagging and cries. It may also have screaming attacks and become more frightened.

In addition, it often happens that your baby sleeps less and less because the sleep routine of your offspring is disturbed. The eating routine can also change, and your baby can have a large or small appetite. Sometimes there can be problems with breastfeeding or drinking from a bottle

12 week boost: what is your baby learning?

From the third month your baby will have the 12 week boost. Your baby’s head hardly needs to be supported. When he wants to see something, he immediately and fluently turns his head from side to side. Your offspring is more active and lively. It kicks and spins in all directions. For example, when changing diapers, they lift their bottom and put their toes in their mouths. With the help of your hand, your baby can pull himself up to sit on his own. When leaning against you, he can sit up unaided.

During the 12-week push, your baby will clearly show you that it is bored and needs a change. Your baby’s behavior shows what it finds beautiful or not. It can behave or react differently to different people it meets.


When your baby sees you, it laughs and kicks its arms and legs and clearly shows its happiness. In this way, your baby will begin to communicate with you and respond to your behavior. It develops new sounds. In addition, your baby will discover squeaking and crowing for itself. It allows them to fade from loud to quiet or vice versa. It tells entire stories with its new language. Your baby will also enjoy making bubbles with his spit.

motor skills

When lying on its stomach, your baby can already hold its head up 30 to 45 degrees. Holding objects over your baby will arouse interest. He starts banging his hands on it and is able to hold it on his own for a brief moment. Your baby thus reaches for objects consciously, purposefully and with both hands. For example, it can shake a rattle . Your baby learns to grasp during the 12 week push.


Your baby will touch their face, eyes, mouth and hair. It feels the hands and the clothes and starts fumbling with them. Your baby starts to put everything in his mouth.

You can encourage your baby’s development by stroking your baby’s hands with different materials. This is helpful because it allows your baby to sense that different things feel different. For example, you could use a quill, brush, wool, fur, or fabric. Through these games, your baby can learn to touch and feel.

How long does the 12 week boost last?

Your baby’s growth spurts begin around the 5th week of life and end in the 56th week of life. This is based on the calculated date of birth and not the actual one.

In most cases, a growth spurt lasts about a week. This is usually followed by a relaxed phase in which your child tests the new skills and you can recover.

Challenges: What are you and baby expecting?

Your baby needs physical closeness during the 12 week push. During this time you need a lot of patience. This phase is not only exhausting for your 12-week-old baby, but also for you. You will be challenged, because your offspring will demand more attention.

Don’t plan on anything big during the 12-week push and concentrate on your child. Does your baby want to be comforted and reassured or does he prefer to be busy and entertained. During this time, a sling or baby carrier can be a real help. It strengthens the bond between you and your offspring.

What should you consider during the 12 week boost?

You should draw your attention to the following.

  • Avoid extra stress
  • Keep calm and be patient
  • Don’t do anything big
  • Loving and understanding treatment
  • Concentrate on your baby

Appointments: What medical examinations are required for the 12-week flare-up?

U4 investigation

From the 12th week your baby should get the U4 examination. Here it is checked whether your baby has developed healthily and has already experienced the 12-week boost.

The Professional Association of Pediatricians and Youth Doctors points out that you must make an appointment with the pediatrician up to the 18th week of your baby’s life, otherwise the examination will be billed as an IGEL service.

The Federal Center for Health Education gives an overview of what is checked during the examination by the pediatrician. A few points play an important role here.

The pediatrician checks the age-appropriate physical and mental development of your baby. In addition, the hearing and vision are examined and the fontanelle is checked so that the skull can continue to grow. You should be able to give the pediatrician information about your baby’s nutrition, digestion and accident prevention, if necessary. If your baby is a crying child , you can also get help. Finally, possible repeat vaccinations are discussed with the pediatrician.


If you have your baby vaccinated, pay attention to the vaccination dates. Before your appointment with the pediatrician, you should inform yourself about the vaccinations. You should have your pediatrician answer any open questions. If you are not sure about your baby’s vaccination, get more opinions.

Baby 12 weeks old: height, weight and clothing size

You can find out how big and heavy your baby can be on average at 12 weeks and which clothing size is the right one in the size table.

girl   guys  
size 52 to 66 cm 52 to 66 cm
Weight around 5,800 g around 6,400 g
increase 110 to 330g 110 to 330g
clothes/ onesie Size 62, possibly also 68 Size 62, possibly also 68
caps Size 37-39 Size 37-39
socks Size 15-17 Size 15-1 7

Please note: These are average values! These can vary from child to child as each child develops differently.

Look forward to new things

The 12 week boost isn’t about your baby growing in size, it’s about your baby’s brain growing by leaps and bounds.

This phase can be a real challenge, but it also fascinates you at the same time. Look forward to the new development of your offspring and avoid unnecessary stress. Because the calmer and more relaxed you are, the more relaxed and happy your baby can be.

Even if it gets exhausting at times, try to remain calm and patient. Observe and enjoy the time with your baby. Enjoy new events. Maybe keep this as a reminder with a photo album or a development calendar, because this time will not come back.

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