Typical motor development part 1

Gestational Age (GA)

Time from the first day of the last menstrual period used to estimate fetal age; postconceptual age is GA minus 2 weeks.

Last Menstrual Period (LMP)

Date used as the starting point to calculate gestational age.

Postconceptual Age / Embryonic Age

Age from conception; equals GA minus 2 weeks.

Full Term

37–42 weeks GA; 40 weeks is commonly used for calculation.

Chronological Age

Days, weeks, or months since birth.

Premature

Birth that occurs before 37 weeks GA.

Corrected (Adjusted) Age

Chronological age minus the number of weeks born prematurely.

Zygote

Fertilized egg; initial stage after conception.

Blastocyst

Early embryo stage before implantation.

Endoderm

Germ layer that gives rise to the digestive tract.

Mesoderm

Germ layer that forms muscles, skeleton, and circulation.

Ectoderm

Germ layer that forms skin and the nervous system.

Neural Tube Closure

Process by which the neural tube closes; critical between Weeks 4–8; defects can cause neural tube defects.

Anencephaly

Absence of the cranial vault; incompatible with life.

Craniorachischisis

Open cranium and spine due to failure of neural tube closure.

Open Spina Bifida

Spinal defect with incomplete fusion of the vertebrae; neural tissue may be exposed.

Encephalocele

Sac-like protrusion of brain tissue through a skull defect.

Omphalocele

Herniation of abdominal contents at the base of the umbilical cord.

Teratogens

Agents (drugs, chemicals, infections, maternal conditions) capable of causing developmental abnormalities.

Critical Periods of Development

Windows during which teratogens can cause specific birth defects or abnormalities.

Prevention of Birth Defects

Early prenatal care; folic acid supplementation (400 mcg daily) before/during pregnancy; avoid smoking, alcohol, and harmful substances.

Folic Acid (400 mcg)

Supplement started before pregnancy to help prevent neural tube defects.

Fetal Alcohol Syndrome (FAS)

Birth defects caused by prenatal alcohol exposure; may include facial features, growth deficiencies, and CNS problems.

Neonatal Abstinence Syndrome (NAS)

Withdrawal symptoms in newborns after abrupt cessation of gestational exposure to substances.

Apgar Score

Neonatal assessment at 1 and 5 minutes evaluating color, heart rate, reflexes, muscle tone, and respiration; ranges guide needed interventions.

Small for Gestational Age (SGA)

Birth weight less than the 10th percentile for gestational age.

Low Birth Weight (LBW)

Birth weight 2500 g (5 lb 8 oz) or less.

Very Low Birth Weight (VLBW)

Birth weight 1500 g (3 lb 5 oz) to less than 1500 g.

Extremely Low Birth Weight (ELBW)

Birth weight less than 1000 g.

Breech Birth

Birth presentation where the buttocks or feet come first instead of the head.

Vertex

Head-down fetal presentation — normal vaginal delivery possibility.

Lanugo

Fine prenatal body hair often present in mid-gestation.

Surfactant

Lung fluid that reduces surface tension; production begins around 24 weeks and matures near late gestation.

Viability

Ability of the fetus to survive outside the womb, generally around 23 weeks gestation with intensive care.

Quickening

Maternal perception of fetal movements, typically in the 17–20 weeks of gestation.