Antenatal care and early pregnancy Flashcards
What is the definition of small for gestational age and of fetal small for gestational age?
SGA: infant with birth weight <10th centile for gestational age (severe= <3rd centile)
Fetal SGA: estimated fetal weight or abdominal circumference <10th centile (again, severe= <3rd centile)
What is the definition of fetal growth restriction?
Then a pathological process has restricted genetic growth potential. This can present with features of fetal compromise including reduced liquor volume (LV) or abnormal doppler studies. Likelyhood of FGR is higher in sevre SGA fetus.
What does ‘constitutionally small’ mean?
- small size at all stages but growth following centiles
- no pathology is present
- contributing factors are ethnicity, sex and parental height
- accounts for 50-70% of SGA fetus
How do placenta mediated growth restrictions tend to present and what can cause them?
- initially the growth is normal but growth slows in utero
- low pre pregnancy weight, substance abuse, autoimmune disease, renal disease, diabetes and chronic hypertension can cause
What can cause a non placenta mediated growth restriction?
fetal factors such as chromosomal or structural anomaly, an error in metabolism or fetal infection (usually CMV)
Give 5 risk factors for SGA?
- maternal age >40
- smoker >11 a day
- previous SGA baby
- maternal/ parental SGA
- previous still birth
- cocaine use
- daily vigorous exercise
- maternal disease eg chronic htn, renal impairment, diabetes, vascular disease
- low maternal BMI
- heavy bleeding
- pregnancy interval <6 months or >60 months
- low pregnancy associated plasma protein (a hormone produced by the placenta)
- if 3 minor RFs or 1 major RF present refer tor uterine artery doppler
What investigations may be appropriate for fetus with small gestational age?
- detailed fetal anatomical survey
- uterine artery doppler
- karyotyping
- screening for infections such as congential cytomegalovirus, toxoplasmosis, syphilis, malaria
How should fetal SGA be managed?
- modify RFs to help prevent SGA
- uterine doppler ultrasound should be primary surviellance tool, if normal repeat every 14 days, if abnormal repeat more frequently or consider delivery
- if delivery is <37 weeks due to absent/ reverse end diastolic flow on doppler then give single course of antenatal do steroids and c section
- if UAD normal then can offer normal induction at 37 weeks
State 4 complications of SGA?
- neonatal complications: stillbirth, birth asphyxia, meconium aspiration, hypothermia, polycythaemia, retinopathy or prematurity, pulmonary haemorrhage, NEC
- long term: cerebral palsy, T2DM, lbesity, HTN, behaviour problems, precocious puberty, depression, alzheimers, cancer (breast, lung, colon, ovarian, blood)
What is large for gestational age?
weight, length or head circumferance in >90th percentile for gestational age
- high birth weight is >4000g (macrosomia)
What is the definition of low, very low and extremely low birth weight?
LBW: <2500g
VLBW: <1500g
ELBW: <1000g
When does symmetrical IUGR present and what causes it?
- 20-30% of IUGR
- Early onset, <32weeks gestation
- causes by things affecting all stages of growth eg genetic disorders and TORCH infections
- While constitutionally SGA fetuses are symmetrically small in their size, they growth hasnt been restricted per se so do not come under IUGR
When does asymmetrical IUGR present and what causes it?
- 70-80% IUGR
- later onset >32 weeks
- chronic hypoxia eg due to placental insufficiency, smoking etc
- malnutrition
- HTN
What risks are involved with LGA foetus’?
- shoulder dystocia
- hypoglycaemia
- metatarsus adductus
- hip subluxation
What can cause LGA?
- poorly controlled gestational diabetes
- genetics: large parent= large baby
- increased maternal age
- obesity
- genetic disorders- beckwith weideman
How may LGA be managed?
- due to increased risk shoulder dytocia, induction of labour usually offered when EFW 4kg
- better to avoid situation so manage RFs
- c section of LGA + maternal diabetes
- can manage as normal pregnancy unless polyhydramnios
What is RBC isoimmunisation?
- production of antibodies in the mum in response to isoantigen on the foetuses erythrocyte
- Commonest example is when a rhesus -ve mum has a rhesus +ve baby
- it occurs when the fetal cells enter the maternal circulation via a sensitiseing event eg antepartum haemorrhage, abdo trauma or during delivery.
- there is rarely any problems during the primary exposure
What disease may occur due to RBC isoimmunisation?
haemolytic disease of the newborn (mum gives baby her antibodies to its own RBCs)
When are anti D immunoglobulins indicated? (9)
In rhesus D negative women, anti D immunoglobulins should be considered following any sensitising event:
- invasive obstetric testing (eg amniocentesis of Chorionic villus sampling)
- antepartum haemorrhage
- ectopic pregnancy
- external cephalic version
- fall or abdo trauma
- intauterine deaht
- miscarriage
- termination of pregnancy
- delivery (normal, instrumental or c section)
The immunoglobulins prevent isoimmunisation during sensitising events.
How should sensitising events at <12 weeks (ectopic pregnancy, molar pregnancy, termination or heavy uterine bleeding) and 12-20 weeks gestation (any sensitising event) be managed?
- maternal blood group and anti body screen (to confirm RhD- and no anti D antibodies already present)
- 250 IU anti D within 72 hrs of event
What is a feto- maternal harmorrhage test?
also known as the Kleihauer test, this assesses how much fetal blood has entered the maternal circulation. If there has been a sensitising event after 20 weeks gestation, this test is used to determine how much anti-D immunoglobulin should be administered
How should sensitising events at >20 weeks gestation be managed? (inc after delivery)
- maternal blood group and antibody screen
- if after delivery also do rhesus status of baby
- feto- maternal haemorrhage test (if after delivery, this test is only done if baby rh+ve and mum rh-ve)
- 500 IU within 72 hrs of event, dose can be increased depening on size of FMH
Describe the RBC isoimmunisation screening and prophylaxis programme in the uk
- all pregnancy woman have maternal blood group (ABO and RhD typing) at booking visit (8- 12 weeks gestation) and again at 28 weeks
- any women found to be RhD- should be offered routine antenatal anti- D prophylaxis (500IU) at 28 and 34 weeks, some centres give a larger dose at 34 weeks.
Define prematurity
any baby born before 37 weeks from the first day of the last menstrual period.
Very prem: 28-32 weeks, extreme prem: <28weeks
What are the main probelms prem babies face immediatly?
- hypothermia (little subcut fat, less able to shiver, high SA:BW)
- hypoglycaemia, esp if SGA and hypocalcaemia
- respiratory distress
- neonatal jaundice
- infection and NEC risk increases
- intraventricular brain haemorrhage risk higher
What may cause premature birth?
- infections
- cervical incompetence (through past cervical surgery, or childbirth etc)
- multiple pregnancies
- pre eclampsia (planned)
- kidney disease (planned)
- growth restriction (planned)
- bleeding after 24 weeks is a RF
- Water breaking too early- unknown why, may be due to smoking, weak cervix, infection, vaginal bleeding
- antiphospholipid antibody syndrmoe
How can high risk of prem birth be managed?
- increased monitoring with transvaginal USS for cervical shortening or funnelling every 2 weeks from 14-28 weeks
- progesterone pessary/ injections if previous Prem birth or cervix length <25mm
- cervical stitch (cerclage stitch) or vaginal stitch if history of preterm birth AND cervic length of <25mm
- fetal fibronectin test- predicts chance of going into labour within next couple of weeks
- steroid injection and and magnesium sulphate before delivery
What is prolonged pregnancy?
pregnancies which persist longer than 42 weeks gestation
What RFs are associated with prolonged pregnancy?
- nulliparity (never having completed a pregnancy beyond 20 weeks)
- maternal age >40
- previous prolonged pregnancy
- high BMI
- FHx prolonged pregnancy
What complications are associated with prolonged pregnancy?
- exponential increase in the risk of still birth
- increased potential for placental insufficiency causing fetal acidaemia and meconium aspiration in labour
- increased risk of need for c section
- neonatal hypoglyacemia due to reduced oxygen and nutrient transfer from placental degradation, depleting glycogen stores