Presentation and Position in Labor

1. Presentation and Position

Presentation refers to the part of the fetus that enters the pelvic inlet first during pregnancy and labor. It’s determined by the presenting part, which is the portion of the fetus that presents to the pelvic inlet. The position of the presentation is defined by the location of the presenting part in relation to the maternal pelvis.

2. Determining Presentation

2.1. Vertex Presentation: The presenting part is the posterior fontanel.

2.2. Face Presentation: The presenting part is the chin.

2.3. Shoulder Presentation: The presenting part is the fetal shoulder.

3. Position of Presentation

The position of the presentation can only be determined during a vaginal examination during labor. It’s defined by the location of the presenting part relative to the maternal pelvis.

4. Types of Presentation

4.1. Longitudinal Lie: The axis of the fetus aligns with the axis of the uterus.

4.2. Transverse Lie: The axis of the fetus is perpendicular to the axis of the uterus.

4.3. Vertex Presentation: There are two types of vertex presentations: occipitoposterior and occipitoanterior.

5. Determining Position of Vertex Presentation

During a vaginal examination, if the posterior fontanel is felt at the 7 o’clock position, the position is right occipitoposterior.

6. Determining Position of Face Presentation

During a vaginal examination, if the nasal bridge is felt at the level of the right iliac crest, the correct position description is right mentoanterior.

7. Diameter of Presenting Part

7.1. Vertex Presentation: The suboccipitobregmatic diameter measures 9.5cm.

7.2. Face Presentation: The submentobregmatic diameter.

8. Position and Vaginal Delivery

A mentoposterior face presentation may allow for vaginal delivery.

9. Presentations Not Suitable for Vaginal Delivery

Brow presentation is not suitable for vaginal delivery.

10. Position

Position refers to the relationship between the presenting part of the fetus and the anterior-posterior location within the maternal pelvis.

11. Determining Fetal Position

To diagnose fetal position, the presenting part’s location within the maternal pelvis is used.

12. Preliminary Diagnosis of Fetal Presentation

An egg-shaped uterus suggests a longitudinal lie.

13. External Abdominal Palpation

A diagnosis of cephalic presentation can be made if the lower pole feels like a hard, round mass with ballottement.

14. Degree of Flexion

Diagnosis of the degree of flexion is only applicable to vertex presentations.

15. Cephalic Presentation

– Maximum flexion is vertex presentation.

– Maximum extension is face presentation.

– Intermediate positions are brow or sinciput presentation.

16. Number of Positions, Presenting Positions, and Vertex Presentations

There are 2 positions, 6 presenting positions, and 2 types of vertex presentations.

17. Types of Vertex Presentation

There are two types of vertex presentations: occipitoposterior and occipitoanterior.

18. The Most Accurate Method of Determining Presentation

Vaginal examination to locate the presenting part is done after cervical dilation.

Conclusion:

Understanding presentation and position is essential for evaluating the status of labor and making appropriate management decisions.