Antenatal Care and Screening in Pregnancy Flashcards
how is sensitivity of a test assessed?
true positive/(positive + false negative)
how is specificity of a test assessed?
true negative/(negative + false positive positive)
what history is done at booking appointment (12 weeks)?
PMH previous pregnancies (including unsuccessful) social history DH surgical history allergies FH mental health FGM - female genital mutilation
naegele’s rule?
predicts an estimated due date based on the onset of the woman’s last menstrual period
- add on 9 months and 7 days
investigations at 12 week booking appointment?
examination - height, weight, BP, CVS, abdo exam haemoglobin antibodies (rhesus) syphilis/HIV/Hep B/C urinalysis (mid stream, culture) US
what is done at normal antenatal management follow up visits?
history - physical/mental health - fetal movements examinations - BP - urinalysis - symphysis - fundal height - lie and presentation (should be longitudinal with head down at 28 weeks) - engagement of presenting part (shouldn't happen before 36 weeks) - fetal heart auscultation
when is fetal anomaly scan done?
20 weeks
what anomalies are checked for at 20 weeks?
- Spina bifida
- Anencephaly
- Cleft lip
- Heart defects
- renal agenesis
- skeletal dysplasia
- edward’s syndrome (trisomy 18)
- patau’s syndrome (trisomy 13)
- Abdominal wall defects
○ Gastroschisis
○ Exomphalos - Placenta previa
○ Low lying placenta
○ Often only transient
Talipes equivarus
several more
what is placenta praevia?
when the placenta is low lying in the womb and covers all or part of the entrance to the womb (cervix)
in most women, as the womb grows upwards, the placenta moves with it so that is in a normal position before birth and doesnt cause a problem
how is placenta praevia seen?
if an earlier US (18-20 weeks and 6 days) shows placenta extending over cervix, another scan should be offered at 32 weeks
if this scan is abnormal a transvaginal scan should be offered
how is down’s syndrome risk assessed?
first trimester
- measure of skin thickness behind neck using US (Nuchal translucency)
measured at 11-13+6 weeks
combined with HCG and PAPP-A
a value < 3.5mm = normal when CRL is between 45-84mm
- higher NT = higher chance of down’s syndrome
2nd trimester down’s syndrome screening?
just a blood test at 15-20 weeks
- assay of HCG and AFP
- UE3
- inhibin A
- not as good as first trimester
how is overall down’s syndrome risk formulated?
combination of measurements at 1st/2nd trimester screening combined with maternal age and gestation to give a personal risk
requires accurate pregnancy dating and detailed counselling
specific diagnostic tests for down’s syndrome?
amniocentesis - done after 15 weeks - sample of amniotic fluid - 1% risk of miscarriage chorionic villus sampling - done after 12 weeks - placenta biopsy - 2% risk of miscarriage
what are the 2 main haemoglobin disorders in pregnancy/foetus?
sickle cell anaemia
thalassemias
both are AR
how can fetal anaemia be picked up?
doppler US
shows increased pressure in middle cerebral artery (baby trying to use all the oxygen it has in the brain)
types of maternal anaemia?
iron deficiency
folate deficiency
B12 deficiency
when is anaemia screened for?
booking (12 weeks) and 28 weeks
how does rhesus haemolytic disease develop?
Rh +ve father and Rh -ve mother conceive a child
child is Rh +ve (from father)
at delivery, Rh +ve baby’s blood enters mother’s bloodstream and invasive Rh +ve blood cells cause the production of Rh antibodies in the mother
these antibodies remain in mother’s bloodstream
when a later pregnancy occurs, the Rh antibodies attach the foetus’s blood cells causing Rh disease
how can the risk of gestational diabetes be screened?
determine following risk factors at booking appointment
- BMI >30
- previous macrosomic baby weighing 4.5kg or above
- previous gestational diabetes
- family history of diabetes (1st degree relative)
- ethnic minority family origin with high prevalence of diabetes
woman with any one of these risk factors is offered gestational diabetes testing
how is gestational diabetes diagnosed?
2 hour 75g OGTT (7.8mmol/litre or above)
fasting plasma glucose (5.6mmol/litre or above)
how is foetal growth monitored?
serial measurement of symphysis fundal height (SFH) at each antenatal appointment from 24 weeks
SFH should be plotted on a customised chart rather than a population based chart
what SFH warrants further investigation (US)?
women with single SFH which plots below the 10th centile
serial measurements which demonstrate slow or static growth by crossing centiles
women in whom SFH may be inaccurate (BMI >35, large fibroids, hydramnios)
who may be at high risk of pre-eclampsia?
hypertensive disease during previous pregnancy CKD autoimmune disease (e.g SLE or antiphospholipid syndrome) diabetes chronic hypertension first pregnancy age 40+ pregnancy interval >10 years BMI 35+ family history of pre-eclampsia multiple pregnancy
what advice is given to people at high risk of pre-eclampsia?
advised to take 75mg aspirin per day from 12 weeks until birth
- contraindicated in asthma, peptic ulcers etc
what is urinalysis used for in pregnancy?
UTI
asymptomatic bacteriuria
PET
diabetes
what blood tests are done at 12 weeks (booking)?
syphilis HIV Hep B/C FBC (anaemia) rhesus status check blood type/antibodies check red cell antibodies
what is checked on 12 week scan?
viability of foetus site of pregnancy (potential ectopic) molar pregnancy multiple pregnancy down's syndrome estimated date of delivery (EDD) - based on crown rump length
what tests are done at 28 weeks?
repeat bloods
- maximise haemoglobin
