Obstetrics + Breast Flashcards
briefly describe the implantation stage of the development of the placenta
- develops from the trophoblast that surrounds the fetus
- 6 days after fertilisation, the blastocyst binds to endometrial lining, trophoblast grows and differentiates to form 2 layers (cytotrophoblast and syncytiotrophoblast)
- syncytiotrophoblast develops finger-like projections (chorionic villi) that invade endometrium to hold the blastocyst in place
- this syncytiotrophoblast produces bHCG by second week - used for pregnancy testing, needed to enable corpus luteum to produce progesterone until placenta is fully developed at week 12
briefly describe the post-implantation lacunar phase of placental development
- on day 9, the syncytiotrophoblast forms lacunae (spaces) within it
- also, it erodes maternal tissues so that blood from uterine spiral arteries flows in and fills these lacunae
- this supplies oxygen and nutrition to blastocyst via diffusion - this is the early maternal circulation in the developing placenta
briefly describe the post-implantation development of the chorionic villae in the placenta
- syncytiotrophoblast invades into endometrium, forming chorionic villi, with the cytotropholast invading into the villi behind that to form an inner layer
- mesenchyme from embryo then invades into the villi, forming core of connective tissue (now got 3 layers)
- mesenchyme then forms blood vessels that link up with newly formed fetal circulation
placenta now has blood supply from mum and fetus for more efficient exchange of nutrients, gases and waste products
briefly describe the further development of the villi/placental circulation, after the formation of tertiary villi
- as villi are forming, cytotrophoblast extends through the syncytiotrophoblast at tip of each villus - these are now in direct contact with endrometrial cells, forming a cytotrophoblast shell that holds embryo in place
- this shell stays connected at the top of chorionic villi, which are surrounded by maternal blood in the lacunae - this is the site of exchange between fetal and maternal blood
- as placenta grows, lacunae become supplied by spiral arteries and endometrial veins (burrow into spaces and become larger with more flow)
- remodelling of spiral arteries creates high flow, low resistance system - if this goes wrong, you might see pre-eclampsia, IUGR, late sporadic miscarriage
which part of the development of placental circulation goes wrong in pre-eclampsia?
the remodeling of spiral arteries to create a high flow, low resistance system
describe the vasculature transporting blood between fetus and placenta
two umbilical arteries, one umbilical vein
describe the structure of the placenta
- maternal blood enters large lacunae from spiral arteries and is drained by endometrial veins
- there’s NO mixing of maternal and fetal blood in placenta
- 2 layers separate fetal and maternal blood in villi, a thin syncytiotrophoblast layer, and a single layer of endometrium in the fetal capillary
- this allows for rapid diffusion between the two circulations
what is the key function of the placenta?
supplies the requirements of the developing fetus, while maintaining an environment in which fetus can grow.
has a high metabolic rate which is useful for protein synthesis, active transport and growth
describe how gas transport occurs between fetus and placenta
O2 and CO2 transported to fetus by passive diffusion.
rapid metabolism of fetus uses up lots of O2 so maintains the concentration gradient compared to maternal blood.
fetal Hb also has high O2 affinity than HbA
when is the implantation window?
days 6-10
describe how nutrient transport occurs between fetus and placenta
combo of passive facilitated diffusion and active transport.
towards the end of pregnancy, excess of nutrients is transported so the fetus can develop gylcogen/fat stores (incl. brown adipose, which then gets broken down early in neonatal life to generate heat)
describe the role of the placenta in immune protection
fetus inherits mostly paternal MHC gene products, so mum’s immune system sees fetus as ‘non-self’
placenta acts as a barrier to prevent immune rejection - syncytiotrophoblast cells as the fetal-maternal interface don’t have MHC antigens so don’t reject baby
what is capacitation?
occurs in the process of fertilisation. changes in sperm cell membranes, results in change of tail movement and allows the acrosome reaction to occur.
what is the acrosome reaction?
exposed acrosome enzymes in sperm erode the zona pellucida to allow fertilisation.
once sperm and egg have fused, changes in zona pellucida occur to block polyspermy
where does fertilization occur? what mechanisms aid sperm transport to this place?
ampulla of the fallopian tube
transported by sperm motility + oxytocin make uterus contract
describe the development from zygote –> blastocyst
zygote = the newly combined sperm and egg.
rapidly divides to form morula (16-32 cells) = ball of cells surrounding a yolk sac
morula develops into blastocyst - cells rearrange themselves into two layers, the inner cell mass (embryoblast, goes on to form the embryo) and the trophoblast.(forms placenta) - blastocyst implants on day 6-7
describe the physiological adaptations to pregnancy seen in the respiratory system
- needs to improve oxygenation and CO2 clearance to support fetus
- lots of women get SOB in pregnancy - because uterus elevates diaphragm by c.4cm, get a decreased reserve vol. and feel out of breath
- but - rib cage circumference expands (relaxin), and minute volume increases so they are fine
- pregnant women live in state of compensated respiratory alkalosis - to do with lowering Co2 in blood to maintain conc gradient so that it’s removed from fetus
describe the physiological adaptations to pregnancy seen in the cardiovascular system
increase in progesterone decreases vascular resistance. results in increased cardiac output.
there’s also activation of the RAAS, resulting in retention of sodium, meaning blood volume increases (physiological anaemia).
constriction of peripheral blood vessels - some women get Raynaud’s.
palpitations are common and pretty normal.
there’s ECG changes but cba to learn them.
describe the physiological adaptations to pregnancy seen in the urinary system
- kidneys get bigger
- GFR increases in first trimester, then falls again - this is responsible for increased urination in first trim, but later in pregnancy that’s due to compression of bladder
- renal blood flow increased - increased clearance of most substances.
- glycosuria is normal
- increased risk of stasis (progesterone relaxes smooth muscles of bladder), increases risk of UTI
describe the physiological adaptations to pregnancy seen in the skin
increased oestrogens can lead to hyperpigmentation, striae gravidarum etc
describe the physiological adaptations to pregnancy seen in the MSK system
- often see changes in posture and gait
- ligaments are softened (progesterone, relaxin) - pubic symphysis
describe the physiological adaptations to pregnancy seen in the GI tract
- nausea (morning sickness) - resolves by weeks 16-18
- progesterone relaxes gut muscle, leads to decreased motility, which leads to constipation and reflux
- less smooth muscle activity in gallbladder raises risk of stones
- loads of women get heartburn - due to reduced motility and also big uterus pushing stomach up
describe the physiological adaptations to pregnancy seen in the reproductive system
- enlarging of the uterus (occurs via hypertrophy of cells, not hyperplasia)
- increased uterine blood flow
- uterus split into upper and lower segments from 3rd trimester
- cervix has an increase in vascularity, swollen, softer
- late in gestation, prostaglandins remodel the cervical collagen
describe the physiological adaptations to pregnancy seen in the breasts
- deposition of fat around glandular tissue, and no. glandular ducts increases
- prolactin prepares alveoli for milk production, and is needed for stimulation of milk secretion
- oestrogen during pregnancy suppresses milk secretion - rapidly falls within first 48h, so that’s when milk comes in
- early suckling helps stimulate pituitary to release prolactin and oxytocin, to initiate lactation
describe the physiological adaptations to pregnancy seen in the endocrine system
- prolactin = anterior pituitary
- oxytocin = produced hypothalamus, stored posterior pituitary
- thyroid = stimulated by bHCG - can imitate thyrotoxicosis
- adrenals = produce more renin and cortisol
- hCG = produced in massive amounts by syncytiotrophoblast, acting to maintain corpus luteum until placenta can take over - peaks days 8-10 then decreases
what are the three stages of labour/delivery?
first stage = between onset of regular contractions and the full dilation of the cervix
second stage = between full dilation to delivery of baby
third stage = from delivery of baby to delivery of placent
what 3 mechanical factors determine progress in labour?
3 Ps:
Powers - degree of uterine force
Passage - dimensions of pelvis and resistance of soft tissues
Passenger - dimensions of fetal head/fetal position
what are the three principle planes of the pelvic passage?
inlet - transverse diameter is 13cm, AP 11cm
mid-cavity - almost round, similar transverse and AP diameters
outlet = AP diameter (12.5cm) > transverse diameter (11cm)
so baby has to turn head as it passes through
what are the ‘stations’ involved in labour?
station = level of head on vaginal examination, measured in relation to ischial spines station 0 = head level with spines station -2 = head 2cm above spines station +2 = head 2cm below etc
when is labour diagnosed?
painful regular contractions in presence of a fully effaced cervix, which is 4cm or more dilated, with or without a show or ruptured membranes
at what rate would you expect cervical dilatation to occur?
roughly 1-2 cm/hour but it’s very variable (lots faster if multiparous)
charted on partogram - highlights slow progress/failure of presenting part to descend (stations)
what 4 bones make up the bony pelvis?
- two innominate bones
- sacrum
- coccyx
which part of the body is responsible for the propulsive contractions that deliver a fetus?
upper segment of the uterus
what causes effacement of the cervix?
contractions generated by upper segment of uterus - it retracts (tightens down), causing lower segment to stretch and thin out
how does a fetus ‘normally’ engage/present for deliver?
usually occipito-transverse or occipitio-anterior position
as labour progresses, neck flexes so the suboccipitiobregmatic diameter is presenting (top of head, smallest diameter at c.9.5cm).
describe the movement of the fetus through the birth canal in a typical OA presentation
suboccipitiobregmatic diameter presenting.
as baby descends, internal rotation brings the occiput into the anterior position when it reaches pelvic floor.
occiput descends below symphysis pubis, then extension of neck around the pubic bone delivers the face (facing floor).
delivery of head brings shoulders into pelvic cavity - baby then restitutes (external rotation) - head turns relative to shoulders, brings shoulders down further and they rotate into pelvic outlet, passing anterior shoulder under pubis (assisted by gentle downward traction on head).
lateral flexion of fetus deliver posterior shoulder, rest of body follows.
describe the components of routine assessment of a woman presenting in first stage of labour
Mum - vital signs, urinalysis, analgesia requirements
Baby - fetal HR pattern (intermittent auscultation or CTG if worried)
Abdo palpation - fetal size/lie/presentation/engagement
Contractions - frequency/duration/intensity
vaginal exam - cervical effacement and dilatation, station and position of presenting part, presence of caput or moulding
liquor - clear, blood stained, meconium
give some examples of analgesia used during labour and when it might be indicated
oxygen/NOS - first stage, inhaled
pethidine - first stage, IM injection
pudendal block - second stage, for operative delivery
perineal infiltration - second stage, prior to episiotomy
epidural anaesthesia - first/second stage, C section
spinal anaesthesia - operative delivery, manual removal of the placenta
what are the active vs passive phases of the first stage of labour?
passive = first 3cm, can take several hours active = 3-10cm, should be 1-2cm dilation an hour, shouldn't last >12 hours
what are the passive vs active phases of the second stage of labour?
passive is from fully dilated until the head hits pelvic floor and woman feels urge to push (lasts only a few mins)
active stage is when mum is pushing - if this takes >1h, spontaneous delivery is unlikely
describe the third stage of labour
delivery of placenta - usually takes 15 mins.
blood loss up to 500ml.
uterine muscle fibres contract to compress blood vessels to placenta which shears away from uterine wall.
describe the typical active management of the third stage of labour
usually IM syntocinon (oxytocin) given with delivery of shoulder.
cord is clamped and cut.
controlled cord traction used once placenta has separated from uterus (involves fundal pressure too I think).
placenta and membranes checked to ensure complete, vagina/labia/perineum checked and estimated blood loss recorded.
give some fetal and maternal indications for induction of labour
maternal - severe pre-eclampsia, pre-existing disease (e.g. diabetes), social
fetal - prolonged pregnancy, IUGR, rhesus disease
what is the Bishop score?
used to assess cervix prior to induction of labour (higher score reflects more favourable cervix)
- unfavourable cervix = hard, long, closed, not effaced
- favourable cervix = soft, beginning to dilate and efface
describe different methods used in induction of labour
prostaglandins - prostaglandin E2 vaginal gel, helps ripen cervix
amniotomy - artificial rupture of membranes using amnihook, used in induction and also to accelerate slow progress in labour
oxytocin - IV infusion of oxytocin (syntocinon) often used, stimulates contractions after amniotomy/spotaneous rupture of membranes
what factors related to the Passages might cause failure to progress?
Pelvis - abnormal shape (loads of causes e.g. osteogenesis imperfecta, cephalopelvic disproportion (suspect if head not engaging, small woman)
Soft tissues - uterine malformation, failure of cervical dilation, past vaginal surgeries, vulva (FGM)
what factors related to the Passenger might cause failure to progress?
fetal size - if they’re chunky
fetal abnormality - esp with neck/skull
fetal malposition - if in OT or OP position
fetal malpresentation - non-vertex e.g. face, brow, breech, shoulder
what factors indicate that Power is the issue causing failure to progress?
monitored by uterine palpation and CTG (although CTG readings altered by position of monitor)
diagnosed with insufficient uterine poser if labour is prolonged and contractions are uncoordinated, fewer than 3-4 in 10 min, lasting less than 60s, pressure less than 40mmHg.
exclude other problems!!! then careful use of IV syntocinon
define malpresentation
what are the common malpresentations?
anything other than vertex presentation
vertex = area between parietal eminences and the anterior and posterior fontanelles.
most common = breech
others = shoulder, brow, face
what is the key risk factor for a breech presentation?
prematurity!
risk at term = 3%
at 32 weeks = 15%
at 28 weeks = 25%
what are the three types of breech presentation?
extended/frank breech - around 50% - hips flexes and knees extended (feet right up by head)
flexed/complete breech - bent at knees and hips
footling breech - feet presenting
how do you diagnose a breech presentation?
head felt as large lump at fundus
auscultation of fetal heart at higher level than usual
vaginal examination (palpation of buttocks as presenting part if in labour)
ULTRASOUND is diagnostic
what are the possible complications of a breech presentation?
big risk of entrapment of head, cos body is softer and smaller so will get through a smaller pelvis than a head will - compression and decompression of head in pelvis can injure the brain.
perinatal mortality due to prematurity, cord prolapse, birth trauma, congenital anomaly
perinatal morbidity - nerve palsies, fractures etc
how do you manage a breech presentation?
recommendation is trial of ECV at 36-37 weeks, followed by ELCS if unsuccessful.
planned vaginal breech delivery is risky but can be performed by skilled midwife - not current recommendation.
list some contra-indications to external cephalic version
pelvic mass antepartum haemorrhage placenta praevia previous C section multiple pregnancy rupture membranes
what is external cephalic version?
attempt to turn fetus to a cephalic presentation by manual manipulation - should be done on labour ward (risk of fetal distress needing immediate delivery - give anti-D if indicated). can use tocolytics and ultrasound as well.
describe baby’s position in a transverse lie. what is the most serious complication you’re likely to see?
long axis of baby is transverse/oblique - sideways basically - shoulder is most likely to present
risk is of cord prolapse - associated with spontaneous rupture of membranes.
what is an unstable foetal lie?
when it’s different every time it’s palpated/assessed
what factors are associated with a transverse lie (alongside those associated with malpresentation in general)?
multiparity - poor tone of uterus and abdo wall
premature labour
second twin
what factors are associated with malpresentation?
maternal - contraction of the pelvis, pelvic tumour, Mullerian abnormality, multiparity
fetoplacental - placenta praevia, polyhydramnios, multiple pregnancy, fetal anomaly
how do you manage a mother with a baby in transverse lie?
try ECV
if not C section probs best bet
if unstable lie - expectant management at term as often converts to cephalic presentation.
if multiple pregnancy and second twin transverse - don’t rupture membranes, try and do ECV to longitudinal lie and then deliver as usual
can you deliver a face presentation baby vaginally?
if it’s metoanterior (chin forward) then yes, but metoposterior won’t
delivery occurs by flexion of head - deliver essentially as for vertex - warn parents of bruising to face, try not to poke baby in eye/splash with antiseptic during vaginal exams
can you deliver a baby in brow presentation vaginally?
not normally as an average-sized fetus will have a brow diameter that’s wider than normal pelvis - obstructed labour.
if small baby/big pelvis - manage expectantly, might present face or vertex
give some indications for an episiotomy
maternal - FGM, previous perineal reconstructive surgery
fetal - instrumental delivery, breech delivery, shoulder dystocia, abnormal CTG
briefly describe how an episiotomy is carried out
ensure adequate analgesia - epidural or perineal infiltration with local anaesthetic
start in midline at posterior fourchette, then incision is made mediolaterally (diagonally) - harder to repair than midline incision, but protects anal sphincter
describe the classification of perineal trauma
1st degree - skin only
2nd degree - skin and perineal muscle
3rd degree - partial/complete rupture of anal sphincter
4th degree - as for 3rd degree, but + anal mucosa
some 1st degree tears can be left to heal themselves if not actively bleeding. the rest require a repair.
give some indications for a ventouse delivery
maternal - delay in 2nd stage due to maternal exhaustion
fetal - delay in 2nd stage due to fetal malposition (OP or OT position), abnormal CTG
list the 5 criteria that must be met before an instrumental delivery is performed
- adequate analgesia - perineal infiltration/pudendal block/epidural
- abdo exam - head either 1/5 or 0/5 palpable
- vaginal exam - fully dilated cervix, head at/below ischial spines, known fetal position
- adequate maternal effort and regular contractions needed for ventouse
- empty bladder needed for forceps
if head is above ischial spines - has to be a c section!
briefly describe the technique used in a ventouse delivery
cup applied in midline, avoiding vaginal mucosa. pressure applied. traction used in time with maternal contractions and effort - initially downwards, then changing angle up as head crowns
give some indications for a forceps delivery
maternal - medical conditions complicating labour, unconscious mother/motherotherwise unable to assist with delivery
fetal - gestation <34 weeks, face presentation, known or suspected fetal bleeding disorder
non-rotational forceps only suitable for direct OA or OP presentation
give some maternal complications of instrumental delivery
genital tract trauma, risk of haemorrhage and/or infection
give some fetal complications of instrumental delivery
ventouse - chignon (scalp oedema) or cephalohaematoma (subperiosteal bleed)
forceps - bruising, facial nerve palsy, depression skull fracture
give some maternal indications for a LSCS
two previous LSCS placenta praevia maternal disease e.g. fulminating pre-eclampsia maternal request active primary genital HSV HIV - where viral load high
give some fetal indications for a LSCS
breech
twin pregnancy if first twin not cephalic presentation
abnormal CTG or FBS
cord prolapse
delay in first stage of labour e.g. due to malpresentation/malposition
briefly describe the procedure of an LSCS
ideally 39+ weeks gestation (reduces risk of TTN in baby)
regional analgesia e.g. spinal/epidural
low transverse skin incision, rectus sheath cut and muscles divided, uterovesical peritoneum incised so bladder can be reflected inferiorly, lower uterine segment incised transversely and baby taken out.
IV oxytocin given by anaesthetists, placenta and membranes removed. uterus closed in two layers with absorbable sutures.
give some possible complications of an LSCS
haemorrhage - always send a group and save, cross-match if high risk for bleed
gastric aspiration - risk if GA used, or in emergency when hasn’t be NBM
visceral injury - damage to bladder or bowel
infection
thromboembolic disease
future pregnancy - VBAC or repeat operations with increasing risk of complications
when might a trial of a VBAC be considered? what extra measures would be done in labour?
if LSCS was done for a non-repeatable cause (e.g. cord prolapse), if counselled appropriately for risk of needing CS.
extra measures basically just preparing in case of scar rupture necessitating immediate C section - cannula, FBC, group and save, continuous CTG etc
define preterm labour
differentiate this from ‘threatened’ preterm labour
labour occurring after 24 week and before 37 weeks gestation
if uterine contractions but cervix is closed = threatened
what drug should ideally be given to mum to protect baby’s lungs if preterm labour is suspected
corticosteroids - IM betamethasone x2 injections, 12 hours apart - ideally.
reduces neonatal respiratory distress by stimulating fetal surfactant.
give some risk factors for preterm labour
BMI <19 low SE status unsupported afro-caribbean ethnic group extremes of reproductive age (<20 or >35 yrs) domestic violence smoking *prev preterm labour* BV chronic medical conditions
give some cause of preterm labour
- infection (20%) e.g. chorioamnionitis, maternal pyelophritis/appendicitis
- uteroplacental ischaemia e.g. abruption
- uterine overdistension e.g. polyhydramnios, multiple pregnancy
- cervical incompetence
- fetal abnormality
- iatrogenic (1/3rd) - when obs think delivery is necessary for fetal or maternal health
list some pathogens implicated in infective causes of preterm labour
- sexually transmitted - Chlamydia, Trichomonas, Syphilis, Gonorrhoea
- Enteric organisms - E coli, Strep faecalis
- BV - Gardnerella, Mycoplasma and anaerobes
- Group B Strep (if very growth)
what is tocolysis? what drugs might be used?
attempting to use drugs to stop contractions and delay delivery (by up to 24-48h) - gives time for steroids to work and for transfer to another hospital if needed.
drugs - atosiban, nifedipine, ritodrine, salbutamol, indomethacin, GTN patches
give some situations which would suggest tocolysis to delay preterm labour is inadvisable
- maternal illness that would be helped by delivery e.g. pre-eclampsia
- evidence of fetal distress
- chorioamnionitis
- if there’s significant vaginal bleeding
- if membrane’s have ruptured
what is cervical cerclage?
used in cases of preterm labour where cervical incompetence means there’s cervical dilation but patient isn’t actively labouring
suture placed in cervix to minimise prolapse of membranes
what is the role of antibiotics in preterm labour?
prophylactic erythromycin given if membranes have ruptured before term
if membranes intact, woman should be swabbed and given abx if needed
does preterm labour affect mode of delivery used?
C section rate might be higher - more due to higher incidence of low-lying placenta, fetal distress and abnormal lie in prematurity.
how does a preterm labour/delivery affect management of future pregnancies?
doesn’t really - high risk for another preterm labour so be aware of that.
describe basic management of a mother presenting with preterm rupture of membranes (PROM)
admit her for 48h as massive risk of preterm labour - rule out chorioamnionitis/sepsis.
give steroids to protect baby’s lungs
erythromycin prophylaxis to prevent ascending infection
what is preterm rupture of membranes (PROM)?
when the membranes rupture, causing flooding/leaking of amniotic fluid, before the baby is term - may or may not be accompanied by preterm labour.
risk is of infection and preterm delivery
what are the two different categories you might put a foetus that is small-for-dates into?
small for gestational age - small for their age, but continuing to grow at a normal rate
IUGR - foetus is small or normal sized but growth rates slowing as pregnancy advances
what placental factors could cause a foetus to be small for gestational age?
abnormal trophoblast invasion - pre-eclampsia, infarction, abruption
causes asymmetrical growth restriction with head sparing and reduced abdo circumference
what foetal factors could cause a foetus to be small for gestational age?
genetic abnormalities, esp. trisomies 13, 18 and 21, Turner syndrome
congenital anomalies
infection e.g. CMV, rubella
multiple pregnancy
list the major risk factors for having a small-for-gestational age baby.
how would the antenatal care of these women be managed?
maternal age >40 smoker cocaine use previous SGA baby prev still birth maternal/paternal SGA chronic hypertension diabetes renal impairment antiphospholipid syndrome heavy antepartum bleeding pre-eclampsia
refer for consultant-led care and have serial US measurements of fetal size, incl umbilical artery Doppler from 26-28 weeks
in considering risk of small for gestational age babies - who should be referred for serial growth scans?
women with a single “major” risk factor - serial US, umbilical artery Doppler at 26-28 weeks.
women with 3+ “minor” risk factors - Doppler at 20-24 weeks, then serial scans if abnormal
any single fundal height measurement <10th centile or incident of static growth should prompt refer for USS - use funal height charts generated for the mum based on her height, age etc etc
list some minor risk factors for having a small-for-gestational age baby
maternal age >35 nulliparity BMI <20 IVF pregnancy-induced hypertension
what is the definition of large vs small for gestational age
small = estimated fetal weight OR abdo circumference <10th centile for their gestational age large = above 95th centile in estimated fetal weight
define gestational diabetes
‘carbohydrate intolerance which is diagnosed in pregnancy and may/may not resolve after pregnancy’
fasting glucose >7mmol/L
>7.8mmol/L 2 hours after a 75g glucose load at glucose tolerance test (NICE)
who is screened for gestational diabetes / how is it diagnosed in pregnancy?
oral glucose tolerance test at 24-28 weeks (or ASAP after booking if prev gestational diabetes or glycosuria).
screen women with RFs: BMI >30 prev macrosomic baby >4.5kg FHx diabetes minority ethnic family origin with a high prevalence of diabetes
what are the possible foetal complications of mum having diabetes?
increased risk of - congenital abnormalities, risk of preterm labour
foetal lung maturity reduced at any age
MACROSOMIA - fetal pancreatic islet cell hyperplasia leads to hyperinsulinaemia and fat deposition - also increased urine output and polyhydramnia
risk of dystocia/birth trauma due to giant baby
more likely to have fetal compromise/distress/death
NB - these typically affect mothers with T1/T2DM rather than gestational diabetes