Prenatal development & infancy

Fertilization

Sperm & Ovum produced by parents, containing 50% of their DNA.
Zygote: a fertilized ovum
- 23 unpaired chromosomes
- Dizygotic & Mono zygotic twins
Myth of the "passive" ovum
"Only 500 eggs" also may be false

Gender bias in science
- Martin, E. (1991). The egg and the sperm: How science has constructed a romance based on stereotypical male-female roles. Signs: Journal of Women in Culture and Society, 16(3), 485-501.

The beginnings of Ontogeny

Everyone began life as a single fertilized cell (zygote) which contained our entire genetic code
Each of us carries a “genetic code” from our parents
This single cell then begins to divide…

Mitosis

All body cells (except the sperm and egg)
- 46 chromosomes in 23 pairs
Body cells reproduce by a process called mitosis
- (except sperm & egg - meiosis)
During mitosis, the cell’s nucleus -including the chromosomes—duplicates itself and the cell divides
2 new cells are formed, each containing the same chromosomes, genes, and DNA as the original cell

Sex and intersex

23rd pair known as "sex chromosomes". XX/XY
- Y chromosome has sex-determining region Y (SRY) protein
- X-linked and y-linked
XXY: Klinefelter syndrome
XO: Turner’s syndrome
XXX: Triple X syndrome
XYY: XYY syndrome
XX SRY-positive karyotype
XY: Androgen insensitivity

Stages of Prenatal Development

First 2 weeks

Carnegie stages 23 stages of first 56 days

Stage 1 (day 1) fertilization of zygote

Stage 2-4 (days 2-6) cleavage, single cell to embryoblast

Stage 5 (days 7-15) Implantation

The Embryo

Weeks 3-8 aka days 14-56 aka stages 5-23

First sign of pregnancy at week 6

The Embryo

10-25% of pregnancies

Prenatal Experience

Movement
- hand to mouth, thumb-sucking, kicking, hand-grasping, punching, twisting/rolling, hiccup
Tactile Stimulation
- own activity, twin’s activity
Smell
- odors in amniotic fluid (from mother’s food)
Taste
- Babies taste the amniotic fluid; develop early preference for flavors in the fluid (from mother’s food)

Prenatal Experience

Hearing
- Voices – rhythm, pitch & prosody (rise and fall)
- Music
- Heartbeat
- Stomach growling
Vision
- Open eyes at 28 weeks
- some bright sunlight can filter through the womb
- can see dim shapes at 33 weeks
- vision is the last sense to develop

Prenatal Learning & Development

Prenatally, children come to prefer familiar tastes and sounds
Newborns recognize the auditory patterns of speech, rhythm and prosody of the language spoken around them
- Babies are born crying in the intonation of their culture’s language
- Study with French vs. German babies
Newborns prefer their mother’s voice to other voices, and prefer stories read by mother while they were in the womb!

Teratogens: Harmful environmental influences

Socioeconomic factors

16% US children born into poverty (2017, record low)
10% Adults uninsured
w/o insurance, childbirth alone coasts $10,000+
- Full pregnancy can costs up to $250,000