Anatomy of pregnancy and labour

Question 1

how do you calculate estimated delivery date

Answer 1

LMP + 12 months – 3 months + 7 days

Question 2

borders of pelvic inlet

Answer 2

is bounded by symphysis pubis, superior border of superior pubic ramus, pectineal line, ilio-pubic eminence, ala of sacrum and the sacral promontory.

Question 3

plane of pelvic inlet

Answer 3

60 degrees

Question 4

borders of the pelvic outlet

Answer 4

bounded by symphysis pubis, inferior margin of inferior pubic rami, ischial tuberosity, sacro-tuberous ligaments and lower sacrum.

Question 5

plane of pelvic outlet

Answer 5

25 degrees

Question 6

what does the pudendal nerve wind around?

Answer 6

ischial spine

Question 7

where do most ectopic pregnancies and fertilisation occur

Answer 7

ampulla

Question 8

muscles of the pelvic floor

Answer 8

levator ani (pubo-coccygeus & ilio-coccygeus) & ischio-coccygeus arising, in continuity, from body of pubis, tendinous arch of obturator fascia and ischial spine.

Question 9

nerve supply of the pelvic floor muscles

Answer 9

S3 and S4

Question 10

describe anatomical changes during pregnancy

Answer 10

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.

Question 11

RFs for ectopic pregnancy

Answer 11

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

Question 12

what does the ectodermal layer give rise to?

Answer 12

to structures maintaining contact with outside world: (CNS, PNS, skin, mammary glands, pituitary, enamel of teeth & the sensory epithelium of eye, ear & nose).

Question 13

what does the mesodermal layer give rise to

Answer 13

gives rise to the ‘supporting’ structures, uro-genital system, spleen, adrenal cortex & vascular system

Question 14

what does the endodermal layer give rise to

Answer 14

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

Question 15

function of amniotic fluid

Answer 15

cushions foetus, absorbs shocks, prevents adherence to amnion, allows foetal movements

Question 16

what is polyhydramnios

Answer 16

excess fluid

Question 17

what is oligohydramnios

Answer 17

reduced fluid

Question 18

describe placental circulation

Answer 18

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

Question 19

what is placenta previa

Answer 19

placenta in lower segment of uterus- lower segment not formed until 32 weeks

Question 20

describe circulation in the foetus at term

Answer 20

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

Question 21

define lie

Answer 21

refers to the longitudinal axis of the foetus in relation to the longitudinal axis of the uterus.

can be longitudinal, transverse or oblique

Question 22

define presentation

Answer 22

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.

Question 23

describe position

Answer 23

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

Question 24

describe attitude

Answer 24

refers to the relationship of foetal parts to one another

Question 25

describe the 3 stages of labour

Answer 25

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