Anatomy of pregnancy and labour Flashcards
how do you calculate estimated delivery date
LMP + 12 months – 3 months + 7 days
borders of pelvic inlet
is bounded by symphysis pubis, superior border of superior pubic ramus, pectineal line, ilio-pubic eminence, ala of sacrum and the sacral promontory.
plane of pelvic inlet
60 degrees
borders of the pelvic outlet
bounded by symphysis pubis, inferior margin of inferior pubic rami, ischial tuberosity, sacro-tuberous ligaments and lower sacrum.
plane of pelvic outlet
25 degrees
what does the pudendal nerve wind around?
ischial spine
where do most ectopic pregnancies and fertilisation occur
ampulla
muscles of the pelvic floor
levator ani (pubo-coccygeus & ilio-coccygeus) & ischio-coccygeus arising, in continuity, from body of pubis, tendinous arch of obturator fascia and ischial spine.
nerve supply of the pelvic floor muscles
S3 and S4
describe anatomical changes during pregnancy
Enlargement of uterus beyond pelvic cavity into the abdominal cavity – by 12 weeks.
Increased vascularity & cellularity of uterus.
Development of lower uterine segment.
Relative shift of uterine tubes due to fundal enlargement.
Softening of cervix & glandular hypertrophy.
Venous congestion of lower genital tract (blue tinge).
Softening & relaxation of ligamentous joints.
Stretching of musculature of the anterior abdominal wall.
Rupture of connective tissue fibres (striae gravidarum).
Increased pigmentation eg linea nigra, cloasma, nipples.
Shift of centre of gravity→lumbar lordosis.
Breast enlargement.
RFs for ectopic pregnancy
Pelvic inflammatory disease IUCD Chlamydial infection Endometriosis Previous appendicitis Abdominal surgery Smoking Incidence 1-2% of live births Up to 5% with assisted conception. Majority (80%) in ampullary region Rarely can be ‘heterotopic
what does the ectodermal layer give rise to?
to structures maintaining contact with outside world: (CNS, PNS, skin, mammary glands, pituitary, enamel of teeth & the sensory epithelium of eye, ear & nose).
what does the mesodermal layer give rise to
gives rise to the ‘supporting’ structures, uro-genital system, spleen, adrenal cortex & vascular system
what does the endodermal layer give rise to
provides the lining of gasto-intestinal tract, respiratory tract, bladder and forms the parenchyma of liver, pancreas, thyroid, parathyroids and the epithelial lining of tympanic cavity & auditory tube
function of amniotic fluid
cushions foetus, absorbs shocks, prevents adherence to amnion, allows foetal movements
what is polyhydramnios
excess fluid
what is oligohydramnios
reduced fluid
describe placental circulation
High pressure in spiral arteries forces blood into intervillous spaces to bathe the villous tree with 02 blood.
In mature placenta, intervillous spaces contain 150mls blood which is replenished 3-4 x per min.
Blood enters foetal vessels which are tributaries of the umbilical vein.
De-oxygenated blood returns to villi by branches of umbilical arteries at low pressure.
Venous blood enters intervillous lakes and flows towards decidual plate to enter endometrial veins.
Placental function involves exchange of gases and metabolic products, hormone production, transmission of maternal antibodies
what is placenta previa
placenta in lower segment of uterus- lower segment not formed until 32 weeks
describe circulation in the foetus at term
Oxygenated blood in umbilical v. → IVC via ductus venosus.
Enters Rt atrium and passes → Lt atrium via foramen ovale.
Passes→ Lt ventricle→aorta→body & umbilcal aa→placenta.
Blood from SVC→Rt atrium→Rt ventricle→pulmonary a.→ductus arteriosus→aorta
define lie
refers to the longitudinal axis of the foetus in relation to the longitudinal axis of the uterus.
can be longitudinal, transverse or oblique
define presentation
refers to the part of the foetus which presents itself in or over the pelvic brim.
Presentation can be cephalic (95%), breech or shoulder.
If head is flexed presentation is called vertex but, with deflexion, brow of face may present.
describe position
refers to the position of the ‘denominator’ - occiput for cephalic presentation (sacrum for breech presentation), with respect to the maternal pelvis.
Position can be right or left and anterior, posterior or transverse
describe attitude
refers to the relationship of foetal parts to one another
describe the 3 stages of labour
Definition: when regular contractions result in effacement & dilatation of the cervix with descent of the presenting part.
Stage I: - Onset of labour → full dilatation of cervix Passive phase (‘effacement’ of cervix) Active phase (dilatation of cervix)
Stage II: Full dilatation of cervix→ delivery of foetus Passive phase (descent of presenting part- no urge) Active phase (maternal effort – irresistible urge)
Stage III: Delivery of foetus→ delivery of placenta/membranes
Passive phase of stage I – variable.
Active phase of stage I – 1cm dilatation per hour.
Passive phase of stage II – maximum of 2 hours
Active phase stage II – maximum of 1 hour
