The Mystery of The Labour Door

The labour door is referred to the cervix.

The Cervix needs to go through 2 stages of changes during the labour:


Stage 1 : Effacement
=> The cervix slowly become thinner and shorter.


Stage 2: Dilatation
=> The cervix is gradually open in diameter.

Pictures below explain the changes of cervix during the labour process.

Picture A & B => The cervix is thick and long. Typically a beginning stage of labour.

Picture C => The cervix is effaced, become thinner and shorter.

Picture D => The cervix start to open after the effacement.

How the doctor measures the diameter of the labour door?


The doctor measures the diameter of the cervix by using the fingers to estimate the width of the cervical opening.



As a general reference,

=> if the diameter is about a slice of banana, then it is 3 cm

=> if the diameter is about a can of soft drink, then it is 7 cm

=> if the diameter is about a size of donut, then it is 10 cm.





The door needs to open to 10 cm before the baby can go through it.
Why the duration of labour is longer in the 1st pregnancy, compared with the 2nd pregnancy ?

As mentioned earlier, the cervix needs to go through 2 stages of changes before it is fully open.

For those expecting their 1st pregnancy, the cervix needs to EFFACE first, then only DILATE....

For those expecting their subsequent pregnancy, the cervix effaces and dilates at the same time.
For this reason, the second pregnancy is faster and easier then the 1st pregnancy.




How fast the labour door can open ?

For those expecting their 1st pregnancy, the door usually opens by 1 cm every hour.

For those expecting their subsequent pregnancy, the door usually opens by 2 cm every hour.




In what conditions the door refuse to open?

=> If the cervix is very thick and long, it will take a long time to open, compare with a thin and short cervix.

=> If the baby is over weight. A big baby is difficult to negotiate through the cervix.

=> If the contraction is weak and irregular.

=> If the pelvic bone is narrow and small.

=> A fibroid or cyst that located next to the cervix sometimes can prevent the cervix from dilating.