The embryo is growing by around one millimetre each day. It is lying in a very curved position in its amniotic sac, which makes it very difficult to measure the entire body length.

To determine its size, the doctor measures the crown-rump length (CRL) instead. This measurement is often noted on the images from the ultrasound examination. All the large internal organs are already present. They will continue to develop and mature over the coming weeks. The beginnings of arms and legs can be easily identified. The skeleton and muscles are forming and the nervous system continues to develop, enabling the embryo to make its first involuntary movements.

You will notice that your breasts are changing. They will become heavy and feel sensitive or sore. The mammary glands are preparing for the production of milk. Your womb has also grown much larger and is already pressing against your bladder. That’s why you will feel the need to urinate more frequently, including during the night.

Your baby is about the size of a blueberry.

Baby Entwicklung Schwangerschaftswoche Heidelbeere 4