Month one

Your uterus: 10 amaz­ing facts

Your Pregnancy - - Contents -


The in­crease in size, weight and vol­ume of the uterus dur­ing preg­nancy is phe­nom­e­nal. It grows from non-preg­nant to preg­nant at term like this: Size: 7.5cm x 5cm x 2.5cm to 30cm x 23cm x 20cm Weight: 50g-60g to 900g-1 000g Vol­ume: 6ml-5 000ml (hold­ing ca­pac­ity of the cav­ity)


The uter­ine mus­cle is the only mus­cle in the body that can con­tract and re­tract. This means that dur­ing a con­trac­tion, when the mus­cle short­ens, it won’t lengthen to the same de­gree once the con­trac­tion has passed. This will con­tinue un­til the mus­cle has “bunched up” at the top of the uterus. Once there, it gath­ers its strength to con­tract and ex­pel the baby.


The walls of the uterus are made up of two dis­tinct tis­sue lay­ers and a third cov­er­ing layer. All three lay­ers are suited to main­tain­ing preg­nancy and then ac­com­plish­ing labour and birth.


Within five days your amaz­ing uterus has made a rapid re­cov­ery and is back where it started, at the be­gin­ning of your preg­nancy. By day 14 it’s the same size as it was be­fore you fell preg­nant. The rest of your body takes a lit­tle longer to re­cover, how­ever!


The uterus has an ex­tremely rich blood sup­ply in or­der to nour­ish the foe­tus dur­ing preg­nancy. Dur­ing late preg­nancy up to one litre of blood per minute passes through the uterus.


The nerve sup­ply to the uterus is com­plex and isn’t yet fully un­der­stood. The pain re­cep­tors re­spond loudly to a di­min­ished sup­ply of oxy­gen and to the sen­sa­tion of stretch­ing. As it’s nec­es­sary for the cervix to stretch in or­der to open, you’ll have to learn how to work with your body to ease the dis­com­fort dur­ing labour. As far as the oxy­gen sup­ply is con­cerned, you can un­der­stand why it’s so im­por­tant for you to breathe through your con­trac­tions, be it with your nat­u­ral breath­ing, or pat­terned breath­ing tech­niques.


Brax­ton-Hicks con­trac­tions are mild and ir­reg­u­lar, but although they re­main pain­less, they grad­u­ally in­crease in fre­quency and in­ten­sity as the preg­nancy nears term. The uter­ine mus­cle tight­ens for about 30 to 60 sec­onds and then re­laxes. Th­ese con­trac­tions fa­cil­i­tate blood and oxy­gen to the placenta and the grow­ing baby. Af­ter 30 weeks they start to in­crease in in­ten­sity and are now thought to be brought about by the in­crease in the level of prostaglandins, and the fact that the uter­ine mus­cle be­comes in­creas­ingly sen­si­tive to oxy­tocin as labour ap­proaches. Th­ese con­trac­tions pre­pare the uterus for labour.


Dur­ing the first stage of labour it’s the func­tion of the uterus to thin out and open up the cervix. Dur­ing the sec­ond stage of labour it ex­pels the baby, with vol­un­tary ef­fort from the mother. Dur­ing the third stage of labour, the uterus has to con­tract tightly to peel the placenta off its walls and to squeeze down firmly so the amount of blood lost from the pla­cen­tal wound site is very lit­tle. This is where the liv­ing lig­a­tures come into ef­fect. As the uterus con­tin­ues to con­tract and re­tract the many blood ves­sels are pinched and bleed­ing stops.


Ac­cord­ing to ob­ste­tri­cian and au­thor Dr Gor­don Bourne, it takes an av­er­age of 150 con­trac­tions to de­liver a first baby, 75 for a sec­ond or third child, 50 for a fourth or fifth and 30 to 40 for sub­se­quent chil­dren.


The uterus con­tracts pain­lessly all the way through preg­nancy, but th­ese con­trac­tions are usu­ally only felt by the mother dur­ing the sec­ond half of the preg­nancy.

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