Fetal position & pelvisFree in the app
Maternal pelvis — diameters
Inlet, midcavity and outlet.
Source: GFMER · epomedicine Calculator
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Inlet
| True conjugate | 11 cm (promontory to top of symphysis). |
|---|---|
| Obstetric conjugate | 10–11 cm — shortest AP; <10 cm = contracted. |
| Diagonal conjugate | 12.5 cm — only one felt clinically. |
| Transverse | 13 cm |
| Oblique | 12 cm |
Mid & outlet
| Interspinous | 10–10.5 cm — narrowest pelvic diameter. |
|---|---|
| Outlet AP | 13 cm (to coccyx tip). |
| Bituberous | 11 cm |
| Subpubic angle | ~90° gynaecoid; <90° android. |
A summary for trained clinicians. Always check the full guideline, the patient in front of you and your hospital's protocol. Spotted an error? Tell us.