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Cervix in Pregnancy

The cervix is the lower cylindrical part of the uterus that projects into the vagina. During pregnancy, the cervix undergoes significant physiological and structural changes to maintain pregnancy and prepare for labor.

It functions as a barrier protecting the uterine cavity from ascending infections and premature expulsion of the fetus, while gradually remodeling to allow cervical effacement and dilation during labor.

Synonyms

  • Uterine cervix

  • Cervical canal

  • Endocervix and ectocervix

Structure and Pregnancy-Related Changes

  • Pre-pregnancy: Firm, long (approx. 2.5–3.5 cm), closed cervical canal

  • During pregnancy:

    • Becomes softer and more vascular (Goodell’s sign)

    • Glands secrete thick mucus → forms mucus plug protecting uterine cavity

    • Cervical length is critical for pregnancy maintenance; shortening or funneling predisposes to preterm birth

  • Late pregnancy: Progressive effacement (shortening) and dilation in preparation for delivery

Relations

  • Superiorly: Continuous with the uterine isthmus and cavity

  • Inferiorly: Projects into the vagina, surrounded by anterior, posterior, and lateral fornices

  • Anteriorly: Related to bladder base

  • Posteriorly: Related to rectouterine pouch and rectum

  • Laterally: Ureter and uterine vessels

Function

  • Provides mechanical support to maintain pregnancy until term

  • Acts as a barrier against ascending infection with mucus plug

  • Remodels to permit cervical effacement and dilation for delivery

  • Provides an anatomical landmark for clinical and radiological monitoring of pregnancy

Clinical Significance

  • Cervical insufficiency/incompetence: Premature shortening and dilation → risk of preterm birth or miscarriage

  • Cervical cerclage: Surgical reinforcement with sutures in cases of insufficiency

  • Cervical cancer in pregnancy: Rare but clinically significant condition requiring multidisciplinary management

  • Placenta previa/accreta evaluation: MRI assessment of cervical involvement important

  • Imaging relevance: Cervical length and morphology assessed in high-risk pregnancies

MRI Appearance

T2 HASTE (T2 GRE):

  • Cervical stroma shows intermediate-to-low signal intensity

  • Cervical canal and mucus appear bright hyperintense

  • During pregnancy: softening and vascular changes make stroma more heterogeneous, with focal hyperintense zones

  • Shortening or funneling of canal can be assessed clearly

T1 GRE:

  • Cervical stroma shows low-to-intermediate signal intensity

  • Mucus plug usually shows low signal unless proteinaceous or hemorrhagic, in which case it appears hyperintense

  • Hemorrhage or cervical pathology can cause localized high signal intensity

MRI image

Cervix in Pregnancy MRI axial anatomy image-img-00000-00000

MRI image

Cervix in Pregnancy mri sagittal image