NurFakhriyyah, LokemanHazli, Alia Nadhirah

Associate Professor Dr Hanifullah Khan

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*This presentation aims to

*Explain what the Lower Uterine Segment (LUS) is

*An outline of it’s anatomical and histological features

*The implications of the LUS in clinicalpractice

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*Uterine enlargement in pregnancy

*by hypertrophy, hyperplasia and stretching of the muscle fibres.

*from 50-60g to almost 1000g at term

*At 7 weeks - the size of an egg;

*At 10 weeks it is the size of an orange and fills the entire pelvis.

*At 12 weeks it rises out the pelvis and palpable abdominally just above the symphysis pubis

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*The lower uterine segment (LUS) is the part of the uterus and the upper cervix which lies between the attachment of the peritoneum of the uterovesical pouch superiorly & the internal cervical os inferiorly.

*The isthmus of the uterus, the lower extremity of which joins with the cervical canal and during pregnancy expands to become the lower part of the uterine cavity

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*With increasing gestation, there is increased stretching of the uterine muscle fibres.

*This results in the formation of the lower segment in the 3rd trimester (28 – 40 weeks).

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*This part of the uterus is thinner contain less muscle fibres and blood vessels.

*This is the site for caesarean section incision.

*The placenta is attached to the more vascular and thicker upper segment.

*In such cases, the placenta is attached partially or completely to the LUS

*Placental attachment is disrupted as this area gradually thins in preparation for the onset of labor. *bleeding occurs at the

implantation site as the uterus is unable to contract adequately and stop the flow of blood from the open vessels.

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*Muscles @ LS:

*relatively weaker layer of muscle

*less blood supply, compared to the upper segment.

*Caesarean operation is done in the lower segment (across the top of the pubic hairline)

*less likely to cause excessive bleeding.

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*The LUS is an important anatomical part of the uterus

*It has anatomical and functional aspects that can be utilized to produce a better outcome in pregnancy and labour

*Attachment of the placenta to the LUS leads to a risk of bleeding

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*Obstetrics by Ten Teachers

*http://www.pregnancy-labour.info/2009/04/changes-in-uterus-during-pregnancy.html