Female Pelvis and Girdle Anatomy

Female Pelvis

• Strong bony structure articulating with lumbar vertebrae superiorly and femoral heads laterally
• Enables pelvic movements
• Protects pelvic organs
• Pelvic floor muscles support bladder, vagina, uterus, and rectum
• Four bones (adult): two pelvic/hip/coxal/innominate bones, one sacrum, one coccyx
• Four joints: two sacroiliac joints, symphysis pubis, sacrococcygeal joint

Pelvic Girdle

• Pelvic bones unite anteriorly (symphysis pubis) and posteriorly (sacroiliac joints)
• Three bones form a deep socket (acetabulum) for the hip joint
• Ilium forms the superior flattened part of the pelvic bone
• Ischium is smaller, forming the inferior part
• Ischial tuberosities felt through buttocks
• Ischial spines felt vaginally, indicating fetal descent
• Pubis forms smallest/anterior part
• Blood vessels and nerves pass through obturator foramen

True and False Pelvis

• Divided into false pelvis (above iliopectineal line) and true pelvis
• True pelvis shape and diameters important for vaginal birth
• True pelvis has: pelvic brim (inlet), pelvic cavity, pelvic outlet

Pelvic Brim

• Oval shape
• Landmarks: sacral promontory, sacral ala, sacroiliac joint, iliopectineal line, iliopectineal eminence, superior pubic ramus, body of pubis bone, symphysis pubis

Pelvic Cavity

• Extends from brim to outlet
• Roughly circular
• Inclined due to spinal curvature; fetus follows curve of Carus
• Pelvic brim at 55° to the horizontal
• Pelvic outlet at 15° due to differences in anterior and posterior wall lengths

Pelvic Outlet

• Ovoid/diamond shaped
• Landmarks: symphysis pubis, pubic arch, ischial spines, ischial tuberosities, sacrotuberous and sacrospinous ligaments, coccyx

Pelvic Diameters

• Four principal diameters: anteroposterior, transverse, two oblique diameters
• Sacrospinous diameter from sacral promontory to iliopectineal eminence (approx 9-9.5 cm)

Pelvic Conjugates

• Anatomical conjugate (~12 cm)
• Obstetric conjugate (smallest diameter ~11cm)
• Diagonal/internal conjugate (~13 cm) estimated via vaginal examination

Pelvic Floor

• Strong structure supporting pelvic contents
• Involved in micturition, defecation, sexual intercourse, and labour
• Consists of two layers of muscles, ligaments, and connective tissue

Deep Muscle Layer (Levator Ani)

• Pubococcygeus: extends from inner pubic bone to coccyx, surrounds urethra, lower vagina, and rectum.
• Iliococcygeus: from inner iliac bone to coccyx, supporting pelvic organs.
• Ischiococcygeus: from ischial spines to lower sacrum and upper coccyx, supporting pelvic joints.

Superficial Muscle Layer

• Ischiocavernosus: from ischial tuberosity to clitoris
• Bulbocavernosus: in perineum, around vagina, embedding in clitoris
• Transverse perinei: from ischial tuberosities to perineum, joining with muscles of perineal body
• External anal sphincter
• External urethral sphincter

Perineal Body

• Area of skin, muscles, and connective tissue between vulva and anus
• Vital part of pelvic floor
• Muscles: bulbocavernosus, transverse perinei (superficial); pubococcygeus (deep)
• Assists in vaginal birth and defecation
• Commonly torn during childbirth

Perineal Trauma

• Degrees of tear (1st to 4th) based on tissue involvement (skin, perineal muscles, anal sphincters)
• 3a less than 50%
• 3b more than 50%
• 3c EAS and IAS torn
• 4th degree tear = injury to anal sphincter complex

Physiological Changes to Pelvis and Pelvic Floor (Pregnancy)

• Relaxing effect of progesterone affects pelvic ligaments and joints, increasing pelvic dimensions and possibly causing back pain (PGP).
• Relaxing pelvic floor muscles useful for birth, but can lead to stress incontinence.

Physiological Changes to Pelvis and Pelvic Floor (Postnatal)

• Pelvic ligaments and joints tighten post-birth.
• Pelvic floor muscles need to regain function
• Early ambulation and exercises can support recovery
• Increased blood flow may result in oedema and bruising
• Perineal damage may be painful

Pelvic Girdle Pain (PGP)

• Pain in front and/or back of pelvis, sometimes affecting hips and thighs
• Can affect symphysis pubis and/or sacroiliac joints

Incontinence

• Significant proportion of pregnant women experience urinary stress incontinence due to elevated intra-abdominal pressure
• Urge incontinence—sudden intense need to urinate.
• Pelvic floor exercises may reduce incontinence

Pelvic Floor Exercises

• Evidence-based information and advice given during antenatal period
• Referral pathway to specialists.
• Specific exercises for those with problems like episiotomy, significant perineal tears, or suspected bladder/bowel injury, and previous history of bladder/pelvic floor problems
• Training and education should consider cultural factors.