Your Growing Baby

Your Growing Embryo...Fetus...Baby !

How amazing is it that two tiny cells, each with only 1/2 the chromosomes required to create a human being, meet in the dark, quiet interior of the woman's fallopian tube where fertilization begins the journey from embryo to fully formed and mature fetus, ready for life outside the womb.
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I am greatly appreciative to the Endowment for Human Development (EHD) for their wonderful and informative website! The EHD is a nonprofit organization dedicated to improving health science education and public health. EHD equips all persons: individuals, educators, clinicians, and governments to help everyone to appreciate, apply, and communicate the science of health & human development.

Fertilization: Egg & Sperm Meet ~ Fertilization begins when a single spermatozoon (sperm) penetrates the zona pellucida, which surrounds the oocyte (egg). This event triggers a reaction called the zona reaction, which dramatically alters the outer membrane and prevents the entry of any additional spermatozoa into the oocyte.

The Early Blastocyst

The cells lining the perimeter of the embryo will help form the placenta and are called trophoblast cells.
These cells bring water, minerals, and amino acids from the nutrient-rich environment outside the embryo into the blastocyst cavity where they can reach the cells of the inner cell mass.

Implantation Well Underway

Implanation occurs early in pregnancy in which the embryo adheres to the wall of uterus. At this stage of prenatal development, the embryo is a blastocyst. It is by this adhesion that the fetus receives the oxygen and the nutrients from the mother to be able to grow. Implantation occurs approximately 9 days after ovulation, ranging between 6 to 12 days.

The Three-Week Embryo

The brain emerges about 2½ weeks following fertilization. By 3 weeks, the major sections of the brain are identifiable. Only 3 weeks and 1 day after fertilization - the heart begins to beat.1 By 4 weeks, the heart typically beats between 105 and 121 times per minute.

Label Key:
1. midbrain
2. forebrain
3. hindbrain
4. somites

The Four-Week Embryo
Through a complex series of folds, the disc-like embryo now has a head and a tail, with buds that will grow into limbs. The beginnings of a spinal column

and muscles are apparent. The embryo is about 4 to 5 millimeters long -- a bit less than 1/4 inch.

At 7.5 weeks, the embryo's:

eyes move forward on the face and eyelids begin to form
palate is nearing completion and the tongue begins to form
gastrointestinal tract separates from the genitourinary tract
essential organs, all, have begun to form; interestingly enough, the embryo goes through 3 sets of kidneys during this time!

10 - 12 weeks, and end of first trimester

The lips are now well formed. The face is capable of many complex expressions.
Baby yawns! The two sides of the roof of the mouth fuse together along the midline and also fuse with the nasal septum above. Fetuses often touch their mouths, sometimes up to 50 times/hr!

3 - 6 months "in-utero" ... growing and growing and growing...

15-19 wks, rotting reflex is well established, which persists after birth to help the newborn find his or her mother’s nipple during breastfeeding. Between 18-20 weeks the external genitalia are easily differentiated. The cochlea reaches adult size within the fully developed inner ear. From now on, the fetus will respond to a growing medley of sounds. By 24 wks (6 months) week your baby's crown-to-rump length is around 8.4 inches and your baby will weigh approximately 1.2 pounds. Although it weighs a little over a pound at this point, your growing baby is still tiny.

7 - 9 months ~ the third trimester. Maturation and laying down body fat.

During the last 11 weeks of pregnancy, the fetus typically doubles in overall weight, while brain weight doubles in the last 9 weeks of pregnancy. Much of the brain’s weight gain is due to the thickening of the myelin sheath around the nerves. By the end of pregnancy, the fetal brain is about a quarter of its eventual size and contains nearly all the neurons it will ever have: perhaps 100 billion. Each of these neurons will eventually synapse with as many as 200,000 other neurons, creating an electrical network of almost incalculable complexity.

HBMS Clients...

If you happen to capture your birth on video with HBMS and wish to share it here on
our website, we would be ever so grateful! Contact Kim for details about sharing your labor & birth photos and video!

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