Third Trimester

From Embryology

Introduction

The fetus in the 8th month

The third trimester is a period of development when the fetus slows in growth in length and begins to increase substantially in weight. Some fetal systems, such as the respiratory system, only now begin to mature just prior to birth.

Immune system, IgG to specific maternal antigens transferred passively across the placenta during the last trimester of pregnancy.


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| Category:Third Trimester

Neural

Dev anat 01.jpg

Comparison of brain growth through the third trimester.

Third Trimester Timeline

(Clinical Week 28-29)

Week
Stage
Event
Clinical third trimester Fetal weight change.jpg Hearing 3rd Trimester - vibration acoustically of maternal abdominal wall induces startle respone in fetus.
27
 
28
  Respire Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs
29
 
30
   

Genital male gonad (testes) descending

31
 
32
   
33
  Neural brain cortical sulcation - primary sulci present PMID:11158907
34
  Neural brain cortical sulcation - insular, cingular, and occipital secondary sulci present PMID:11158907
35
   
36
 
37
   
38
Birth Galletti1770 birth.jpg Clinical Week 40

Heart pressure difference closes foramen ovale leaving a fossa ovalis

Thyroid TSH levels increase, thyroxine (T3) and T4 levels increase to 24 h, then 5-7 days postnatal decline to normal levels

Adrenal - zona glomerulosa, zona fasiculata present

References


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Cite this page: Hill, M.A. (2024, March 29) Embryology Third Trimester. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Third_Trimester

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G