Fetal Development

Why is accurately determining gestational age important?

To estimate fetal maturity

What are the 3 ways to determine GA?

1. Crown-to-rump measurements

2. Biparietal diameter: transverse diameter of the head

3. Combination: head and abdominal circumference & femur length

When is Crown-to-rump used?

1st trimester

In what week is the diaphragm structually complete?

Week 8

In which weeks could a fetus have a chance of extra-uterine survival? And why?

Weeks 22-24

• immature surfactant is created here

Why do we care about the SA of lungs?

• to determine if the lungs have enough SA to do gas exchange once born

Embryonic period is from what week to what?

Week 3-10 ish

What key things happen in the embryonic period?

• Week 8= diaphragm complete

• Right & left lung buds

• formation of major airways up to segmental bronchi

When does the pseudoglandular period take place?

Weeks 5-18

What key points happen during the pseudoglandular period?

• continued branching of terminal

• pulmonary artery and veins form

• cilia and cartilage appear

When does the canalicular period take place?

Weeks 16-26

What key points happen in the Canalicular period?

• Primitive alveoli (where gas exchange could happen)

• Immature surfactant

When does the saccular period occur?

Weeks 24-37

What key points occur in the saccular period?

• surfactant detectable in amniotic fluid

• gas exchange

• functioning alveoli

When does the alveolar period occur?

Weeks 36-term

What key points occur in the alveolar period?

• secondary seperation

• alveoli multiply

When does first breaths begin? And what does it look like?

After embryonic period

• intermittent diaphragmatic movements followed by periods of apnea

Why is the baby is breathing after the embryonic period?

training the diaphragm like a muscle so needs practice

During periods of apnea and the glottis is closed what is this doing for baby?

• creates pressure (stretches) so that the lung can grow

• pushes fetal lung fluid as well to grow

Babies who are born preterm what do they need to continue to promote growth after delivery?

CPAP so that they can use some pressure to grow the lungs (due to the fact they did not have enough time to grow before being born)

When fetus is breathing and glottis is open what happens?

• Some fetal fluid leaks out into amniotic fluid as exhaled

• some swallowed

What is another way we might be able to figure out fetus’s lung maturity?

recording surfactant in amniotic fluid

In what week are major lung lobes segmented?

Week 12

What period does the membrane between the nose and mouth disapear?

Psuedoglandular

Survival of babies born in Cannicular period is based on?

How much SA is available for Gas exchange

2 types of alveolar cell types

1. Type 1: form A/C Membrane

2. Type 2: produce surfactant starting around 24 weeks

At what week does true alveoli start to appear?

Week 30

How does gestational diabetes affect baby?

• prolonged exposure to insulin = decreased lung maturity

  • Baby might look large and healthy but their lungs still immature = DON’T LET SIZE FOOL YOU

What does surfactant do?

lowers surface tension at air-filled interface of lungs

• helps alveoli’s stay inflated

Why is surfactant important?

• maintain FRC

• can give prophylactically at birth to reduce risk of RDS

What is the BEST way to predictor lung maturity

Gestational age