Third Trimester

Introduction

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.

Historic Embryology
1940 Fetus Physiology
Carnegie Fetal: 95 \| 96 \| 142 \| 145 \| 184 \| 211 \| 217 \| 300 \| 362 \| 448 \| 449 \| 538 \| 590 \| 607 \| 625 \| 662 \| 693 \| 847 \| 858 \| 922 \| 928 \| 948 \| 972 \| 1318 \| 1388 \| 1455 \| 1591 \| 1597b \| 1656 \| 1686 \| 2250a \| 2250b \| 3990 \| 5652 \| 6581 \| 7218

Third Trimester Timeline

(Clinical Week 28-29)

Week	Stage	Event
	Clinical third trimester	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	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

Search Pubmed: Third Trimester

Next: Birth

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, April 24) Embryology Third Trimester. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Third_Trimester

What Links Here?