Your Baby Weeks 1-8

Your baby is growing and changing every week after conception.

Many of our expecting mothers want to know more about the development of their baby.

Your Baby Weeks-1-8

To help provide some of this information to our patients, we will be highlighting the development stages of a baby over a series of blog posts.

In this post, we are focusing on your baby in weeks 1-8.

Truthfully, this is the most critical period of the pregnancy.

During the first week, the development of your baby starts immediately after fertilization (when the male sperm and female oocyte (egg) meet in and unite to form the zygote).

If more than one egg is released from the ovary, twins may develop.

The developing zygote has 46 chromosomes – 23 from you and 23 from the father.

These chromosomes will ultimately dictate the baby’s gender, size, hair and eye color, etc.

From there things happen quickly.

These two cells start to multiply and will migrate from the tube where they met to the uterus where they will implant around week 4.

The placenta then starts to develop which will supply all of the nourishment the developing fetus will need.
Weeks three through eight are called the Emrbyonic Period.

Most, if not all, of the major tissues and organs are formed during this time. During this time the neural tube (or spinal cord) will close.

Important Note: Taking folic acid supplements through prenatal vitamins will help prevent neural tube defects like Spina Bifida at this point in your pregnancy.

By the end of this period, an ultrasound can be used to measure the crown-rump length – from head to tail. And at 7-8 weeks, the embryo will measure 26-30 mm, the size of a large almond.

The limbs have started to develop and the heart is beating at around the 6th week.

At the completion of the Embryonic Period – the neural tube, the heart, and all major organ systems have formed.

This entire process is called organogenesis.


At any time, if you have questions about your pregnancy, please feel free to contact us.