Basic Biology of Fetal Development

Prenatel Development

The Science Abortion-Choicers Try to Ignore

When Canada decriminalized abortion in 1969, technology did not exist to let the world see inside the womb. To a certain extent, abortion advocates in that era of scientific ignorance who honestly believed the unborn was merely a “blob of tissue” might be excused. But thanks to modern microscopic imaging and video technology, we can now see the newly created human being inside the womb. The following chronology of human development is adapted from the book Defending Life, by Francis J. Beckwith. Click the images to enlarge them.

Day 1 - Fertilization

The life of each individual member of a species begins at conception. That is when a genetically new and genetically complete individual first comes into existence. The new being inherits 23 chromosomes from the female germ cell (ovum) and 23 from the male germ cell (sperm), to form a full diploid set of 46 chromosomes and thus, its own human genomic sequence.
For the purpose of classifying stages of human development, biologists label the initial one-celled human organism a "zygote". However, it is an undisputed biological fact that the zygote is an individual being who is alive and is of the human species.
It is a misnomer to refer to this entity as a "fertilized ovum". For both ovum and sperm cease to exist at conception. The new being that arises is a distinct, individual human life, separate from the life of the mother and of the father.
From this point until death, no new genetic information is needed to make the unborn entity a human being. Her genetic make-up is already established, determining to a great extent her individual physical characteristics – gender, eye colour, bone structure, hair colour, susceptibility to certain diseases, etc.
As with the rest of us, all this entity needs to survive is oxygen, food, water and a healthy interaction with her environment. This human organism does not acquire its humanness at some later stage in it's development. She remains a human being throughout her life, from zygote to embryo to fetus to newborn to adolescent and throughout adulthood until natural death, at which time the existence of the living organism ends.

Day 2 - 7

The early human being increases to over 100 cells within the first week after conception.
Implantation occurs 6 days after after conception when the unborn entity "nests" into her mother's uterus

Day 12 - 17

The "primitive streak" - precursor to the nervous system - appears.

Day 18 - 20

By the end of the 20th day, the foundation of the child&'s brain, spinal cord and entire nervous system will have been established.
From a scientific point of view, it is indisputable that this tiny little thing is in fact, a very small human. It is not performing any human activities yet, it’s not reasoning yet, but what it is doing is something that only a human being can do. It is growing a human brain and nervous system⁽¹⁾. So it is not a "potential human being" as abortion-choice advocates claim. It’s a potential adult.

Day 21

A primitive heart muscle begins to pulsate.
Other organs begin to develop during the first month such as a liver, umbilical cord, kidneys and a digestive tract (albeit in their incipient forms).
This organism has a head with a developing face with nascent ears, mouth and eyes, even though it is no larger than the size of of half a pea”.⁽²⁾

Day 26 - 28

Arms and legs begin to appear as tiny buds.
The first month ends with a fully formed human embryo. Again, the term "embryo" describes a stage of human development up to the 8th week, not a different type of being that is somehow non-human. The word embryo is a noun derived from the adjective embryonic, which is used to describe an embryonic human being, just like we'd talk about an infantile human being, as an infant, or an adolescent human as an adolescent.

Day 33

By this day the cerebral cortex, that part of the central nervous system that governs motor activity as well as intellect may be seen.
By the beginning of the 2nd month, the tiny unborn person bears a more familiar appearance that one can easily identify by sight as "distinctly human". Of course it is already human from the moment of conception.
At this stage the mother likely does not know she is pregnant.

Day 40 - 43

Brain waves can be detected although they could very well be ocurring weeks earlier.
During the 2nd month the unborn has reflexes and her lips become sensitive to touch.
Her heart beats and her blood, with its own type begins to flow.

Day 49

By the end of the 7th week, we see a well-proportioned, small scale baby.
Even though it is less than an inch long [2.5cm] and weighs 1/30th of an ounce, it bears all the familiar external features and all the internal organs of the adult human.

Second Month

By the end of the 8th week her own unique fingertips begin to take shape.
The heart beats strongly as the unborn’s stomach, liver and kidneys perform the tasks for which they were designed.
"After the eight week no further primordia will form; everything is already present that will be found in the full term baby". ⁽³⁾

Third Month

Movement is what distinguishes the third month of pregnancy from the first two.
Although just an ounce in weight and no more than a goose egg in size, the unborn begins to display movement including swallowing, squinting, swimming, sucking her thumb and grasping her hands.
It is possible to observe parental features in the unborn’s facial expressions.
"The vocal cords are completed. In the absence of air, they cannot produce sound. The child cannot cry aloud until birth although he is capable of crying long before". ⁽⁴⁾

Fourth Month

Growth is characteristic of the 4th month.
The weight of the unborn expands sixfold by end of the month, a time at which she is about 8 to 10 inches in height or about 50% of what she will be at birth.

Fifth Month

The unborn becomes viable. That is, she has the ability under our current technological knowledge, to survive outside her mother’s womb. Some babies have survived as early as 20 weeks after conception.
This is also the month when the mother begins to feel the unborn's movements.
Rapid eye movement (REM) sleep can be observed in the unborn; she is likely dreaming.

Six to Nine Months

In the remaining 4 months of pregnancy, the unborn continues to develop.
During this time she responds to sounds, her mother’s voice, pain, and the taste of substances placed in the amniotic fluid.
The child is born approximately 38 weeks after conception.

Footnotes

Peter Kreeft, Pro-Life Logic, www.peterkreeft.com (a talk given at Georgetown University 10/19/06)
In his book Defending Life (pp71), Francis Beckwith quotes Krason, Abortion, 341.
In his book Defending Life (pp71), Francis Beckwith quotes an Amicus Curiae, cited in Schwarz, The Moral Question of Abortion, pp 3-4, in his book Defending Life, pp71.
Ibid., 2