L3: Fetomaternal Relationships Flashcards
Definition of Lie
Relation of longitudinal axis of fetus to longitudinal axis of mother.
Types of Lie
Longitudinal Lie
Longitudinal axis of fetus is parallel to that of mother
Transverse lie
Longitudinal axis of fetus is perpendicular to that of mother
Oblique lie
Longitudinal axis of fetus forms acute angle è that of mother
Unstable lie
Not fixed for 24 hours
Def of Presentation
- Part of fetus that occupies LUS, is firstly felt by vaginal examination, will descend 1st in natural birth canal & is 1st to be delivered.
Types of Presentation
- Cephalic presentation (96%)
- Breech presentation (3.5%)
- Shoulder presentation (0.5%)
- Complex (compound) presentation
- Cord presentation
Cephalic presentation (96%)
Presenting part is head
Theories of Cephalic presentation
Gravitational theory:
- Head (heavy part) gravitates by its weight in lower part of uterus late in pregnancy.
Accommodation theory:
- As fetal body becomes larger in size in relation to head in late pregnancy, fetus is adapted to shape of uterus (head occupies the narrow LUS while breech occupies the wide fundus)
Types of Cephalic presentation
Breech presentation (3.5%)
Presenting part is podalic pole (buttocks ± LLs)
Shoulder presentation (0.5%)
Presenting part is shoulder
Complex (compound) presentation
≥ 1 fetal limb beside head or breech
Cord presentation
Umbilical cord presents below one of the above presentations.
Def of Position
- On abdominal examination: Relation ( ) fetal back & anterior abdominal wall of mother.
- On vaginal examination: Relation ( ) denominator & walls of maternal pelvis.
Def of Denominator
Bony landmark on presenting part used to denote position.
Examples of Denominator
1) Occiput: In vertex presentation.
2) Mentum (chin): In face presentation.
3) Frontum (frontal bone): In brow presentation.
4) Sacrum: In breech presentation.
5) Scapula: In shoulder presentation.
Types of Positions
Positions in vertex presentation
OA positions (80%) are more common than OP positions (20%), Why?
1) Concavity at front of fetus (due to flexion) fits into convexity of vertebral column at back of mother (lumbar lordosis).
2) Engaging diameter in OA positions is SOB (9.5 cm) while in OP positions it is OF (11.5 cm).
LOA position is more common than ROA position & ROP position is more common than LOP position, Why?
- In the common positions, head engages in Rt
oblique diameter of pelvic inlet which is slightly longer than the Lt one.
Def of Attitude
Relation of fetal parts to each other.
Typical Fetal Attitude
- fetal attitude: Generalized flexion è head bent in front of chest, arms & legs are folded in front of body & back is slightly curved.
Types of fetal head Attitude
1) Complete flexion: Chin approaches chest wall (the usual attitude).
2) Deflexion.
3) Military position: Midway ( ) flexion & extension.
4) Partial extension.
5) Complete extension: Occiput approaches back.
Def of Synclitism
- Presence of sagittal suture midway ( ) symphysis pubis & promontory of sacrum.
Def of Asynclitism
- Lateral inclination of fetal head making sagittal suture lies nearer to either promontory of sacrum or symphysis pubis & parietal bones not lie at the same
horizontal level (one parietal bone is lower than the other).
Incidence of Asynclitism
- Occurs when true conjugate diameter is shortened (as in contracted flat pelvis).
- Mild degree of asynclitism may occur in normal labor.
Significance of Asynclitism
- ↓↓ engaging transverse diameter of fetal head to allow its passage through pelvis [supraparietal subparietal diameter (9 cm) enters pelvis instead of BPD (9.5 cm)].
Types of Asynclitism
- Naegele’s obliquity
- Posterior asynclitism
- anterior parietal bone presentation
- Litzmann’s obliquity
- anterior asynclitism
- posterior parietal bone presentation
Def of Engagement
- Passage of largest transverse diameter of presenting part (BPD in vertex presentation) through plane of pelvic inlet
- Selection of transverse diameter is done to eliminate effect of change in fetal head attitude which will change the engaging longitudinal diameter).
Time of Engagement
Time of Engagement
- Primigravida
- Usually occurs in last 3-4 weeks of pregnancy due to strong abdominal wall & uterine muscles).
Time of Engagement
- Multigravida
- May occur normally at start of 2nd stage of labor.
Significance of Engagement
Excludes disproportion ( ) presenting part & pelvic inlet.
Dx of Engagement
- Hx
- Ex (Abdominal & Vaginal)
- INVx
Dx of Engagement
- Hx
- Disappearance of upper abdominal pressure symptoms & appearance of lower abdominal & pelvic
pressure symptoms.
Dx of Engagement
- Abdominal Ex
Abdominal Ex in Dx of Engagement
Abdominal Ex in Dx of Engagement
- 1st Pelvic grip
Failure to grasp presenting part.
Abdominal Ex in Dx of Engagement
- 2nd Pelvic Grip
Fingers of both hands are divergent & hands can’t be insinuated below head
Abdominal Ex in Dx of Engagement
- Role of fifths (Crichton’s technique)
Vaginal Ex in Dx of Engagement
Def of Station of presenting part in pelvis (Delee stations)
It is the relation of leading point of presenting part to ischial spines.
Ischial spines are midway …..
( ) pelvic inlet & outlet.
Station of presenting part in pelvis (Delee stations)
- Description
INVx to Dx Engagement
Ultrasound or X-ray.
Causes of non engagement of head in last 3-4 weeks of pregnancy in primigravida
Causes of non engagement of head in last 3-4 weeks of pregnancy in primigravida
- Faults in Power
a) Atony of abdominal wall.
b) Tonic LUS.
Causes of non engagement of head in last 3-4 weeks of pregnancy in primigravida
- fauls in Passages
a) Placental previa.
b) Contracted pelvis.
c) Pelvic bone tumors.
d) Pelvic mass.
e) Rigid cervix.
f) Tough vagina.
g) Full bladder & rectum.
Causes of non engagement of head in last 3-4 weeks of pregnancy in primigravida
- Faults in Passengers
a) Malpresentation & malposition.
b) Short cord or cord around fetal neck.
c) Polyhydramnios or oligohydramnios.
d) Macrosomia.
e) Hydrocephalus.
f) Multifetal pregnancy.
