Prenatal and teratogens

Germinal Period

The first period of prenatal development (about 14 days), lasting from conception to implantation of the fertilized egg in the uterine lining.

Zygote

The new cell formed when sperm and egg unite, containing combined genetic information from both parents.

Blastocyst

The organism after about 5 days of mitosis (100 cells), consisting of an inner group (embryonic disk) and outer group (trophoblast) of cells.

Embryonic Disk

The inner group of cells in the blastocyst that will become the embryo.

Trophoblast

The outer group of cells in the blastocyst that becomes the support system nourishing the developing organism.

Embryonic Period

The prenatal period starting the third week (after implantation) through week 8, when major body structures form; the organism is called an embryo.

Placenta

A structure connected to the uterus that provides nourishment and oxygen from mother to embryo/fetus via the umbilical cord.

Cephalocaudal Development

Prenatal growth proceeding from head to tail; structures nearest the head develop before those nearest the feet.

Proximodistal Development

Prenatal growth proceeding from the midline outward; structures nearest the torso develop before those further away (like hands and fingers).

Fetal Period

The prenatal period from the ninth week until birth, during which major structures continue developing and the organism is called a fetus.

Age of Viability

The point at about 24 weeks gestation when the fetus has its first chance of survival outside the womb.

Neural Plate

The location of stem cells in the embryo (appearing by the third gestational week) capable of producing all the different cells that make up the brain.

Neural Tube

Formed from the neural groove by the end of the third week; the open region in its center forms the brain's ventricles and spinal canal. By week 8, differentiates into forebrain, midbrain, and hindbrain.

Neurogenesis

The formation of neurons; largely completed after five months of gestation (except in the hippocampus, which continues throughout life).

Gray Matter

Regions of the brain containing neuron cell bodies, which appear gray.

White Matter

Axons that form neural pathways, covered in myelin (a fatty, white-appearing substance) that aids in insulation and efficient neural transmission.

Teratogens

Environmental factors (maternal diseases, pollutants, drugs, alcohol) that can contribute to birth defects.

Teratology

The study of factors that contribute to birth defects.

Critical Period (teratogen timing)

The time when a specific body structure is forming and is most vulnerable to severe damage from teratogen exposure (e.g., ears/arms around 6 weeks after conception).

Factors influencing teratogen impact

Timing of exposure, amount of exposure, number of teratogens, genetics (of both mother and child), and being male (more vulnerable) vs. female.

Fetal Alcohol Spectrum Disorders (FASD)

An umbrella term for the range of effects that can occur due to alcohol consumption during pregnancy; the leading preventable cause of intellectual disabilities in the US.

Fetal Alcohol Syndrome (FAS)

The most severe form of FASD; children share features like flattened noses, small eye openings, small heads, poor judgment/impulse control, and lower IQ.

Binge Drinking (pregnancy risk)

4 or more drinks in 2-3 hours during pregnancy, which increases the chance of having a baby with FASD.

Thirdhand Smoke

Toxins from tobacco smoke that linger on clothing, furniture, and surfaces; prenatal exposure has a greater impact on altered lung function than postnatal exposure.

Tobacco use during pregnancy (risks)

Associated with low birth weight, ectopic pregnancy, placenta previa, placenta abruption, preterm delivery, stillbirth, SIDS, birth defects, and learning disabilities.

Neonatal Abstinence Syndrome

When a baby becomes addicted to a drug used by the mother during pregnancy and goes through withdrawal after birth.

Toxoplasmosis

An infection caused by the parasite toxoplasma gondii (found in undercooked meat, unwashed produce, cat feces); can cause premature birth, stillbirth, and birth defects to the eyes/brain.

Rubella (German Measles) risk window

If contracted during the first three months of pregnancy, can damage the eyes, ears, heart, or brain; deafness is almost certain if contracted before the 11th week.

HIV mother-to-child transmission risk

Without antiretroviral drugs, about 25%; with antiviral medication during pregnancy, risk drops to less than 2%.

Lead exposure (prenatal)

Linked to fertility problems, high blood pressure, low birth weight, prematurity, miscarriage, and slowed neurological development.

Mercury exposure (prenatal)

Can cause brain damage and affect the baby's hearing and vision; why pregnant women are cautioned about fish consumption.