Fetal Development

Germinal period

Prenatal development period from 0 - 2 weeks

Characterized by rapid cell division and implantation into uterus (day 8)

Embryonic period

Prenatal development period from 3 - 8 weeks

Characterized by development of 3 layers of tissue and appearance of primitive structures

Fetal period

Prenatal development period from 9 weeks to birth

Characterized by maturation and rapid growth

Critical period

A specific time in development when any adverse event has the most significant consequences that cannot be changed later. Phases have clear and distinct time periods

If proper stimuli is not received, the development will be permanently altered

Sensitive period

A time in development where the embryo is the most prone to adverse effects, but which can be overcome (with some difficulty) later in life

The fuzzy edges at the end of a critical period

1st trimester movements

Fetus can bring hands to face and midline, jaw motion begins, can bend and stretch, breathe, and begin reaching with UE

2nd trimester movements

Fetus can hiccup, startle, and stretch. Begins moving UE, LE, mouth, and trunk

3rd trimester movements

Gross movement decreases due to space limits, but facial movement increases as a circadian rhythm develops

Primitive reflexes

Those which appear in utero and are commonly used to evaluate neural systems function

Full term infant characteristics

Good general movement including spontaneous kicking and flailing

Reflexes are well developed and respond quickly to initial stimuli

Baby tends towards physiological flexion

Preterm infant characteristics

General movement is poor quality or diminished

Reflexes are slow, may require multiple stimuli, or not fully developed

Baby may tend towards extension due to low muscle tone

SGA

Small for gestational age

LGA

Large for gestational age

IUGR

Intrauterine growth restriction

Commonly seen in multiples

Low birth weight (LBW)

Babies born at < 5 lbs or 2500 grams

Very low birth weight (VLBW)

Babies born at < 3.3 lbs or 1500 grams

Extremely low birth weight (ELBW)

Babies born at < 2.2 lbs or 1000 grams