Anatomy of pregnancy

Question 1

What does this describe: the space between the pubic symphysis, superior boarder of pubic crest, pubic tubercle, pectineal line, iliopubic eminence, arcuate lines, alar of sacrum & sacral promontory (S1 body)?

Answer 1

The pelvic inlet

Question 2

What does this describe: wider antero-posteriorly; transverse ~11cm, AP = ~11.5; 25 degree angle to horizontal?

Answer 2

the pelvic outlet

Question 3

What does this describe:

Separates true (above) & false (below) pelvis

60 degrees to horizontal (angle of inclination) - pelvis tilted, ASIS and pubic tubercle in same vertical plane

wide _transversely (_transverse ~13cm, AP (conjugate) ~12cm)

Answer 3

The pelvic inlet

Question 4

What does this describe:

diamond shaped, pubic symphysis, inferior pubic rami, ischial rami, ischial tuberosity, sacrotuberous ligament. coccyx?

Answer 4

pelvic outlet!

[diamond shaped, pubic symphysis, inferior pubic rami, ischial rami, ischial tuberosity, sacrotuberous ligament. coccyx]

Question 5

What route does the foetus take in the bony pelvis?

Answer 5

the pelvic axis

Question 6

What muscles make up the pelvic floor?

Answer 6

Levator ani

• iliococcygeus
• pubococcygeus
• puborectalis

& coccygeus muscle on each side

+ anterior support by perineal membrane & muscles in deep perineal pouch

Question 7

What shape / gender pelvis are these?

• android
• anthropoid
• gynaecoid
• platypelloid

Answer 7

• android = male
• anthropoid = long antero-posteriorally
• gynaecoid = female
• platypelloid = wide laterally

Question 8

At what spinal level does the dura mater terminate at?

Answer 8

• S2

(cauda equina ~L1-L5; comes off conus medularris ~T12)

Question 9

What changes to the uterus occur during pregnancy?

Answer 9

Uteral changes:

• Enlargement of uterus beyond pelvic cavity into the abdominal cavity – by 12 weeks (tri. #1)
• Increased vascularity & cellularity of uterus.
• Development of lower uterine segment.
• Relative shift of uterine tubes due to fundal enlargement.

Question 10

What changes occur to the genitals during pregnancy?

Answer 10

• Softening of cervix & glandular hypertrophy.
• Blue tinge of lower genital tract due to Venous congestion

Question 11

What changes occur to the skeleton during pregnancy?

Answer 11

• Softening & relaxation of ligamentous joints.
• Shift of centre of gravity→lumbar lordosis.

Question 12

What changes occur to skin/tissues in pregnancy?

Answer 12

• Breast enlargement.
• Stretching of musculature of the anterior abdominal wall.
  
  • –>Striae gravidarum from Rupture of connective tissue fibres - e.g. stretch marks
• Increased pigmentation eg
  
  • linea nigra,
  • cloasma,
  • nipples.

Question 13

during delivery how does the foetus:

1) enter
2) turn
3) extend
4) get shoulders out?

Answer 13

1) enters transversely
2) turns 90 degrees @ pelvic floow
3) extends neck when it reaches ischial spines
4) turns 90d again to get shoulders out

Question 14

Where does the babys head need to fit between for delivery?

Answer 14

needs to fit between the symphysis pubis and sacrum - e.g. the biparietal diameter of the baby’s head ~9.5cm

• TF you want the babys occiput anterior (symphysis pubis) and head tucked in - makes smaller diameter

Question 15

When is the uterus palpable O/E?

Answer 15

10-12wks

e.g. end of tri. #1

Question 16

When does the uterus reach the umbilicus?

Answer 16

20wks

Question 17

When does the uterus reach the xipisternum?

Answer 17

• at 36 wks

Question 18

When can you start measuring fundal height (cm)?

Answer 18

roughly corresponds to gestational age in weeks between 16 - 36 weeks

Question 19

What is the ideal/normal positioning for a foetus at term?

Answer 19

• longitudinal lie
• cephalic presentation
• L occiput –> anterior position
• head not yet engaged
• listen on shoulder for HR
• symphiso-fundal height ~consistent with age

Question 20

At what stage of labour does the foetal head enter into the pelvic inlet transversely?

NB: remember the pelvic inlet is wider transversely

Answer 20

in the 2nd stage of labour

Question 21

When is the foetal head described as “engaged”?

Answer 21

when the head lies in the true pelvis

e.g. 3/5ths of the head felt in the abdo

NB: the true pelvis is above the pelvic inlet and the false pelvis is below

Question 22

What turns the babys head 90 degrees when they reach the pelvic outlet and why?

Answer 22

the levator ani (pelvic floor) turns the babys head 90 degrees

because the pelvic outlet has a greater AP diameter

Question 23

At what anatomical landmark does the babys neck extend at when it reases?

Answer 23

the babys neck extends when it reaches the ischial spines

Question 24

What does restitution refer to during labour?

Answer 24

restitution = the second 90 degree turn allowing the baby’s shoulders to be delivered

Question 25

what injury becomes possible at "restitution" during labour?

Answer 25

**upper brachial plexus (Erbs palsy)** injury is possible at restitution e. g. restitution = where the shoulders are able to be delivered due to the 2nd 90 degree turn * NB:(the first was turning the head 90 deg. to go into the pelvic outlet that has a greater AP diameter)*

Question 26

What is shoulder dystocia?

Answer 26

An obstetric emergency! where the shoulders become **stuck** & the babys **thorax is compressed**

Question 27

How do you feel for the position of the foetus? which is the widest part of the foetal head?

Answer 27

feel fontanelles! anterior/posterior aka the longitudinal diameters are the widest part of the foetal head

Question 28

What position of the baby during delivery does this describe? * Baby’s face to sacrum * Feel anterior fontanelle - at 6 o’clock (sacrum is 12 o'clock) * Smallest diameter, one that presents optimally in labour

Answer 28

Occipito-anterior position (ideal) * head flexion * head deflexion

Question 29

What position of the baby during delivery does this represent? * -Baby’s face to pubic symphysis * -Feel baby’s eyes on delivery * -Anterior fontanelle at 12 o’clock is delivery possible?

Answer 29

* Occipito-posterior position (rotated this way by pelvic floor) * Delivery possible

Question 30

What position of the baby during delivery is this: Feel baby’s eyes, nose & mouth on delivery is it deliverable?

Answer 30

* brow presentation * abdominal delivery necessary! * e.g. occipito frontal diameter / mento-vertical diameter is big so --\> c section

Question 31

What does it mean if a baby is coming out with the sub-mento-vregmatic diameter?

Answer 31

* this means the ramus of mandible to centre of anterior fontanelle e.g. * _FACE PRESENTATION!_ * the head is completely extended unlike occipito-frontal/mento vertical (brow px) * in theory vaginal delivery of face px is possible if the chin is anterior... TF if _mento-anterior - allow vaginal delivery_ * if _mento-posterior_ = no more flexion is possible for baby to come out --\> C-SECTION

Question 32

What does it mean if O/E you feel the sacrum of the baby?

Answer 32

Breach position! - RCOG recommends all breach delivered abdominally * can be complete = where knees are bend and feet and bottom are closest to birth canal * incomplete = one of babys knees bent * frank = both legs straight - just bum at bottom * footling = one foot out other knee bent Can deliver vaginally (if trained person around?) if FRANK/EXTENDED breach

Question 33

How would you deliver a frank breach baby? (in theory)

Answer 33

1. rotare baby so back is uppermost 2. pull each leg out in turn 3. let baby hang 4. pull each arm out in turn 5. then pull out head

Question 34

How do you perform manual pelvimetry?

Answer 34

if fist fits between ischial tuberosities, baby will fit

Question 35

What are the 2 types of cepalo-pelvic disproptortion and what do they mean?

Answer 35

1. absolute * the baby is never going to get out (maybe due to pelvic shape) 2. relative * the position of the baby is impairing delivery e.g. occipito-posterior ir de-flection of foetal head

Question 36

What is looked for in a vaginal exam done _during labour?_

Answer 36

1. station of presenting part in relation to the ischial spines 2. dilation (if full dilation = cant feel cervix) 3. feel sutures & fontanelles

Question 37

What does -2 or +1 station mean?

Answer 37

the station is the presenting part in relation to the ischial spines -2 = 2cm ABOVE ischial spines +1 = 1cm below ischial spines

Question 38

in feeling sutures and fontanelles: what is moulding and caput?

Answer 38

caput is associated with moulding * **Moulding** = compression of head, * AKA can feel _sutures overlying eachother_ * **Caput** = _cant feel_ the sutures and fontaelles because of swelling from squashing of head--\> _occludes lymphatic/venous return_ --\> swelling!

Question 39

Why are fontanelles useful for guiding forceps?

Answer 39

fontanelles guide placement of forceps so as not to cause _fractured skull_

Question 40

How are pelvic measures taken in obstetrics using imaging? Why is this useful? What parameters are looked at

Answer 40

* MRI is used - no radiation * these measurement help predict the liklihood of successful vaginal delivery, they look at: * Sagittal inlet and outlet, * & inbetween: maximum transverse inlet diameter, bispinous outlet

Question 41

What are the landmarks of sagital inlet and sagittal outlet seen on MRI for pelvic measures in obstetrics?

Answer 41

sagittal inlet: between sacral promontory (S1) & top of pubic symphysis sagittal outlet: top of coccyx to inferior margin of pubic symphysis

Question 42

Where does ectopic pregnancy most commonly occur?

Answer 42

in the ampulla

Question 43

what conditions predispose to ectopic pregnancy?

Answer 43

anything kind of blocking/scarring the area? 1. infection 2. PID 3. chlamydia 4. appendicitis 5. fibrosis from endometriosis 6. coil!

Question 44

What are the 3 main killers in pregnancy?

Answer 44

1. Haemorrhage 2. hypertensive disorders 3. venos thromboembolism

Question 45

What are the 4 grades of pelvic diaphragm tear?

Answer 45

1. fourcechette & superficial perineal _skin_ & _vaginal mucosa_l 2. extends to perineal _muscles_ and _fascia_ 3. extends to anal sphincter 4. extends to rectal mucosa (e.g. breaks rectal wall) NB: even if not torn, muscles weaken after surgery

Question 46

What does this this describe: incision made into **perineal body** to enlarge the vaginal orifice & **allow** the **head** of the **fetus** to pass through vagina? Why is it done and what variations are there?

Answer 46

Episiotomy = done to cause less trauma to the peritoneum * Median cut - incises the perineal body * Medio-lateral - incision 45 degrees from the midnline * --\> *avoids* the perineal body, * ---\> instead cuts the bulbospongiosus and superficial transverse muscle

Question 47

Why can the foetal anomaly scan happen at 12 weeks?

Answer 47

at 12 weeks the foetus is fully formed and just needs to grow e.g. brain, palate, heart chambers, femur length, head, abdomen

Question 48

When is the early pregnancy USS scan done and what can it show?

Answer 48

early pregnancy USS scan 6-11w scan shows if there is a: * pregnancy/ * ectopic/ * age/ * foetal HR present to determine the age of foetus = use crown-rump length

Question 49

What are the 3Ps of labour?

Answer 49

* Passenger * Passages * Power

Question 50

What factors of "passenger" affect labour?

Answer 50

* babys head measurements * position

Question 51

What factors of "passages" affect labour?

Answer 51

1. engagement of foetal head 2. boundaries of pelvis - inlet and outlet 3. pelvic tilt 4. levator ani muscles - the origin and insertion 5. perineaum - implication & tears, episiotomies

Question 52

What factors of "power" affect labour?

Answer 52

these involve things affecting the UTERUS - which contracts to expel baby * Anatomy: corpus & cervix, 3 layers, oxytocin * nerve supply: symp = lumbar splanchnic, para = pelvic splanchnic * --\> these are affected by: * Epidural * pudendal nerve block

Question 53

What are the stages of labour?

Answer 53

* stage 1 * effacement & dilation of cervix (latent) * after 3cm --\> dilation occurs at 1cm/hr = active * stage 2 * full dilation & expulsion of foetus * Stage 3 * expulsion of placenta

Question 54

What do these represent? * Fully dilated * Occipital position * Ruptured membranes * Contractions * Empty bladder & episiotomy * Pain relief * Station (in relation to ischial spines)

Answer 54

the criteria for instrumental delivery!

Question 55

What is a morula?

Answer 55

* \>32 cell ball... * too many cells to count * Happens by **day 4!**

Question 56

What is a blastocyst?

Answer 56

* the name of the morula _once it has entered the uterus_ * It is a ball of cells _& cyst of fluid_ happens by day 5!

Question 57

What are the 3 layers of a blastocyst? What do they do?

Answer 57

* trophoblast * cells of blastocyst that invade endometrium and myometrium --\> secrete bhCG * chorion * becomes placenta * amnion * becomes amniotic sac

Question 58

Where does the early embryonic nutrition come from?

Answer 58

* reliant on cytoplasm inherited from oocyte * & histiotrophic * uterine secretions * haemotrophic * vascular contact between foetus and mum

Question 59

When is the "window for implantation"?

Answer 59

Day 5-6 e.g. after the blastocyst has formed from the morula on D4 upon entering the uterus

Question 60

When does the trophoblast produce bhCG?

Answer 60

at day 10 this maintains the corpus luteum which produces progesterone to prepare the endometrium for preg (= decidualisation) --\> vital until placental steroidgenesis (trophoblast supplys the embryo with nourishment and later forms the major part of placenta) Its maximum amount of bhCG occurs at 9-11 weeks (only needed in early stages)

Question 61

What can the bhCG levels produced by the trophoblast be used for?

Answer 61

* the basis of urinary pregnancy tests (qualitative measurement of beta subunit) * if bhCG falls = dx miscarriage * if bHCG rises *too slowly* = could be an ectopic pregnancy

Question 62

What are the functions of the placenta?

Answer 62

1. Steroidogenesis 2. nutrition 3. removal of waste 4. barrier: against infection e.g. bacteria, viruses AND drugs 5. antibodies

Question 63

Why is the placenta useful for antibodies?

Answer 63

passes IgG on = passive immunity NB: rubella gets across placenta

Question 64

What steroids are produced in placental steroidogenesis?

Answer 64

* oestrogens * progesterone * Human placental lactogen (breaks down fats from mother to give for fuel to baby) * cortisol

Question 65

What nutrition does the placenta provide and what waste does it remove?

Answer 65

Gives: O2, carbs, fats, AA, vitamins, minerals removes: CO2, urea, NH4, minerals

Question 66

What contains a huge low pressure uterine blood supply, has a huge reserve in function e.g. can lose parts of the uterus and still function & has a huge surface area in contact with maternal blood?

Answer 66

the placenta!

Question 67

What is the end purpose of these tissues invading the mothers uterus 1. syncytiotrophoblast 2. cytotrophoblast 3. extraembryonic mesoderm

Answer 67

1 invades first then 2 then 3 they move down into linings and blend the mesoderm differentiates into--\> blood vessels and "pools" of maternal blood are found the end point ==\> **mature branched vili** (theoretically there is TF no mixing of foetal/maternal blood: in practice a little bit always mixes)

Question 68

What disorders of the placenta are there/what can they cause?

Answer 68

* Miscarriage: 15% pregnancies * Ectopic pregnancy * Hydatidiform mole: genetic, excessive trophoblastic activity (e.g. supposed to supply embryo with nourishment) can cause chorio-carcinoma * Pre-eclampsia * Placenta insufficiency: under-perfusion & growth restriction of the baby * Transfer of drugs, toxins, infections to foetus

Question 69

the trophoblast supplys the embryo with nourishment and later forms the major part of placenta. What are the stages of trophoblast invasion ~10 when it produces bhCG?

Answer 69

1. Early invasion 2. decidualisation - thick layer of modified mucous membrane lining uterus 3. stromal reaction - becomes oedematous/connective tissue 4. angiogenesis - BV to provide nouishment etc 5. erosion of the uterine decidua and glandular tissue by trophoblast = BV/mature villi left