In pregnancy at week 6, the embryo is about the size of a pea or a lentil, about 0.2 inches (4 millimeters) long. The embryo has doubled in the size since the previous week. And this week, they will double in size again.
The folds in your little one’s head have started to form a face. Even though they still look a bit like a tadpole, their jaw, and cheek are starting to take shape. The embryo still has a month to go, but their facial features are already being determined.
By pregnancy at week 6, the embryo’s heart is changing from a simple, tube-like structure to a four-chamber organ. It is already beating and sending blood through the developing circulatory system. The heart is about the size of a poppy seed, and it beats 105 to 110 times per minute. It will beat even faster as it continues to develop.
Ears are starting to form, but right now, they look more like dimples. These tiny holes are located on each side of the head, and they will eventually become fully formed ears. There are also dark sports made by future eye cells, marking the place where the eyes will form.
Other vital organs, including the lungs, kidneys, pituitary gland, intestines, and liver, are starting to develop.
The neural tube is starting to close and will be completely closed by nine weeks. The brain is one of the first organs to develop and the last to finish. The cells that will become the brain and nervous system line up in a strip down the back of the embryo.
At six weeks, this line of cells rolls up into a tube that will be closed by nine weeks. This tube continues to curve and fold into the brain and spinal cord. This is a particularly important time of development’ and the neural tube is very sensitive to exposure to toxins or infections.
The embryo is also starting to move its limbs, which look like tiny paddles right now. A fine layer of translucent skin has formed to cover their body. A six-week-old embryo still has a tail, which is a normal part of the development process. This tail will be gone by the time a baby is born.
The early stages of pregnancy can be fairly exhausting; there is so much happening physically with both you and the baby. Your bump might still be unnoticeable, but the embryo is growing at the fastest rate it ever will. Throughout the entire pregnancy, the baby’s weight will increase three billion times.