First Trimester
This occurs when the blastocyst attaches to the uterine wall.
What is implantation?
This organ begins to form in week 3 and beats by week 5.
What is the heart?
The critical period for heart development is during these weeks.
What are weeks 3-8?
This reflex, essential for feeding, develops around week 28.
What is the sucking reflex?
This temporary organ forms from chorionic villi and provides respiration, nutrition, and excretion for the fetus.
What is the placenta?
By this week, the primitive heart begins to pump.
What is week 3?
These organs start developing in week 5 and produce urine by week 9.
What are the kidneys?
Neural tube defects can occur if this nutrient is deficient in early pregnancy.
What is folic acid?
The fetus begins to hear sounds outside the uterus around this week.
What is week 16?
This fluid-filled sac surrounds and protects the developing fetus.
What is the amniotic sac?
This structure forms from the ectoderm and becomes the brain and spinal cord.
What is the neural tube?
This organ begins to form in week 3 and starts producing blood cells by week 6.
What is the liver?
Exposure to teratogens during this period can cause major structural abnormalities.
What is the embryonic period (weeks 3-8)?
Fetal movements, often called this, are typically felt around weeks 16-20.
What is quickening?
This structure connects the fetus to the placenta and contains two arteries and one vein.
What is the umbilical cord?
These three primary germ layers form during gastrulation.
What are the ectoderm, mesoderm, and endoderm?
These start to develop in week 4 and begin to move by week 9.
What are the limb buds?
This system is particularly vulnerable to alcohol exposure throughout pregnancy.
What is the central nervous system?
This protective substance begins to cover the fetus around week 20.
What is vernix caseosa?
This membrane forms the outer layer of the amniotic sac and contributes to placenta formation.
What is the chorion?
This membrane forms around the embryo and fills with amniotic fluid.
What is the amnion?
This organ starts forming in week 3 and has lobes by week 8.
What is the brain?
Cleft lip may occur if fusion of these processes is disrupted around week 6.
What are the maxillary and nasal processes?
Lung maturity is indicated by the production of this substance around week 35.
What is surfactant?
These maternal blood-filled spaces in the decidua basalis allow for nutrient and gas exchange.
What are the intervillous spaces (or lacunae)?