Maternity - Fetal Development Lecture (Exam One)

Pre-embryonic stage

first 14 days

fertilized ovum becomes a morula and then blastocyst before entering the uterus

Embryonic Stage

The second stage of prenatal development, lasting from two weeks until the end of the second month. (weeks 2-8)

Implantation occurs by the end of week 2.

Neural tube fuses at the center and tubular heart begins to beat in week 3. (Importance ofd 100 mcg of folic acid)

Respiratory and digestive tracts begin to form and the neural tube fusion is complete in week 4.

Limb buds appear in week 5.

In week 6, the heart is in its final form.

In week 8, the first brain waves are detectable.

Exposure to Teratogens during Embryonic Phase

neural tube is fusing during this stage of fetal development

When is surfactant produced?

24th week - if not produced, alveoli will collapse

When does heart rate variability increase and why is it significant?

weeks 29-34, subcutaneous fat deposits begin and the ??? is more pronounced due to central nervous system maturity

Ultrasound is done at several points during a pregnancy. Be able to list the "typical" times an U/S might be done and for what reason during a pregnancy

First Trimester (7-12 weeks):

Confirm pregnancy and detect fetal heartbeat.

Estimate gestational age and determine due date.

Check for multiple pregnancies (e.g., twins).

Assess maternal anatomy and detect uterine abnormalities.

Second Trimester (18-22 weeks):

Anatomical survey to evaluate fetal development and detect structural abnormalities.

Determine sex of the baby, if desired.

Assess placenta position and amniotic fluid levels.

Third Trimester (28-40 weeks):

Monitor fetal growth and position.

Evaluate placental location and function.

Assess amniotic fluid volume and fetal well-being.

AFP/Multiple Marker- what is the difference between these 2 tests and when are they done.

Alpha-Fetoprotein (AFP) Test:

Measures AFP levels in maternal blood.

Conducted between 15-20 weeks of gestation.

Screens for neural tube defects (e.g., spina bifida) and abdominal wall defects.

Multiple Marker Test (Triple or Quad Screen):

Measures AFP plus additional hormones (e.g., hCG, estriol, inhibin-A).

Performed between 15-20 weeks of gestation.

Assesses risk for chromosomal abnormalities, such as Down syndrome (trisomy 21) and trisomy 18, in addition to neural tube defects.

CVS- what is this test, when is it done,

What:

Invasive diagnostic test involving the extraction of chorionic villi from the placenta.

When:

Typically performed between 10-13 weeks of gestation.

Pros and Cons CVS

Early detection of chromosomal abnormalities and genetic disorders.

Provides definitive diagnosis, allowing for earlier decision-making.

Cons:

Carries a small risk of miscarriage (~0.5-1%).

Potential for limb defects if performed before 10 weeks.

Does not detect neural tube defects; additional testing may be require

Amniocentesis

Purpose:

Diagnostic test to analyze amniotic fluid for chromosomal abnormalities, genetic disorders, and neural tube defects.

Can assess fetal lung maturity in later stages of pregnancy.

Typically performed between 15-20 weeks of gestation.