Antenatal care and screening Flashcards
Any screening programme should be
- highly sensitive
- highly specific
- have a high positive predictive value
- easily used in a large population
- safe and cheap
- quick and straightforward to perform
- able to detect a disease with a known natural history and where early diagnosis has a proven benefit
What is sensitivity
True positive /(positive + false negative)
What is specificity?
True negative/(negative + false positive)
What happens at the booking visit?
- History:
- Menstrual
- Medical
- Obstetric
- Family
- Social
- Examination:
- Ht; Wt; BP; CVS; Abdomen
- Investigation
- Hb
- ABO; thesus
- syphillis; HIV; hep B&C
- Urinalysis; MSSU C&S
- Ultrasound
What is the purpose of the US at the booking visit
- confirm viability
- singleton/multiple pregnancy
- estimate gestational age- explain most accurate time/method to establish EDD
- detect major structural anomalies that may be identified in early pregnancy
- offter DSS
What is done at antenatal follow up visits?
- History:
- Physical and mental health
- Fetal movements
- Examination:
- BP and urinalysis
- Symphysis- fundal height
- Lie and presentation
- Engagement of presenting part
- Fetal heart auscultation
What are the objectives of ultrasound screening for foetal anomaly?
- reduction in perinatal mortality and morbidity
- potential for in utero treatment
- identification of conditions amenable to neonatal surgery
Major structural abnormalities occur in _-_% of pregnancies
Major structural abnormalities occur in 2-3% of pregnancies
What do the NHS Fetal anomaly screening programme guidelines say?
“All pregnant women should be offered the 18+0 to 20+6 weeks fetal anomaly scan by a midwife or clinician (at first contact visit and/or booking visit).”
What is placenta praevia?
When the placenta is low lying in the womb and covers all or part of the entrance (the cervix)
If an early ultrasound scan between 18 weeks and 20+6 weeks detects placenta praevia what should be done?
Offered another abdominal scan at 32 weeks and if this is unclear a vaginal scan
How is the down’s risk assessment carried out in first trimester?
Measure of skin thickness behind fetal neck using ultrasound (nuchal thickness)
Measured at 11- 13+6 weeks
Combined with HCG and PAPP-A
A value of <3.5mm would be considered normal with the CRL is between 45 and 85mm
What sould all pregnant woman undergoing down’s screening have before blood is taken?
A dating USS to accurately establish gestation
CRL is only used up to 13 weeks and HC should be used after this
What is done in down’s assessment in 2nd trimester?
Blood sample at 15-20 weeks
Assay of HCG and AFP
What should be done for women who miss 1st trimester down’s screening
- Maternal Age + Biochemical Markers
- Alpha-fetoprotein (AFP)
- human Chorionic Gonadotrophin (hCG)
- unconjugated oestradiol (UE3)
- inhibin A
What are the specific antenatal diagnostic tests?
Amniocentesis
Chorionic villus sampling
When is amniocentesis performed and what is the miscarriage rate?
after 15 weeks
1%
When is chorionic villus sampling performed and what is the miscarriage rate?
After 12 weeks
2%
What are the major haemoglobin disorders?
HbS and thalassemias
What is maternal anaemia?
When is it screened for?
Iron deficiency, folate deficiency, B12 deficiency
Screened at booking and 28 weeks
What is important in the management of maternal anaemia?
Hb should be optimised prior to birth
When should all women have their blood group antibody status determined?
At booking and at 28 weeks gestation
How does Rh haemolytic disease develop?
When father is Rh positive and mother is Rh negative
Baby is Rh+, at birth Rh positive babies blood cells enter mother’s bloodstream
Invading Rh +ve blood cells cause the production of Rh antibodies
Rh antibodies remain in mothers bloodstream
The Rh antibodies attack the babies blood cells, causing Rh disease.
What mental health screening questions should be asked to mothers?
- Do you have new feelings and thoughts which you have never had before, which make you disturbed or anxious?
- Are you experiencing thoughts of suicide or harming yourself in violent ways?
- Are you feeling incompetent as a mother, as though you can’t cope or feeling distanced or estranged from your baby? Are these feeling persistent?
- Do you feel you are getting worse?
How should risk of gestational diabetes be assessed?
At the booking appointment;
- BMI above 30kg/m2
- previous macrosomic baby weighing 4.5kg or above
- previous gestational diabetes
- family history of diabetes (first-degree relative with diabetes)
- minority ethnic family origin
If women have risk factors for gestational diabetes what test should be done?
2 hour 75g oral glucose tolerance test
+ve if woman has;
a fasting plasma glucose of 5.6mmol/litre or above
OR
a 2 hour plasma glucose level of 7.8mmol/litre or above
What are the major risk factors for SGA?
- maternal age > 40
- smoker >11 cigarettes a day
- paternal SGA
- cocaine
- daily vigourous exercise
- previous SGA baby
- previous stillbirth
- maternal SGA
- chronic hypertension
- diabetes with vascular disease
- renal impairment
- antiphospholipid syndrome
- heavy bleeding similar to menses
- PAPP-A <0.4 MoM
What are the minor risk factors for SGA?
- Maternal age >35
- IVF singleton pregnancy
- nulliparity
- BMI <20
- BMI 25-34.9
- smoker 1-10 cigarettes per day
- low fruit intake pre-pregnancy
- previous pre-eclampsia
- pregnancy interval < 6 months
- pregnancy interval > 60 months
If mum has 3 or more minor risk factors then what should be done?
Reassess at 20 weeks
UAD at 20-24 weeks
If normal then assessment of fetal size and umbilical artery doppler in third trimester
If mum has one major risk factors then what should be done?
Reassess at 20 weeks
PAPP-A <0.4 MOM
Fetal echogenic bowel (major)
What is PAPP-A
Placental associated plasma protein A
What is foetal echogenic bowel?
observation in antenatal ultrasound imaging
fetal bowel appears to be brighter than it is supposed to be.
It is a soft marker for trisomy 21 and has several other associations.
needs to be interpreted in the context of other associated abnormalities
What is recommended at each antenatal appointment to predict SGA neonate
serial measurement of symphysis fundal height from 24 weeks of pregnancy
Which women should be considered for ultrasound measurement of fetal size?
women with a single SFH which plots below the 10th centile or serial measurements which demonstrate slow or static growth by crossing centiles
What is important about the plotting of SFH?
Needs to be plotted on a personalised chart
In which women is measurement of SFH inaccurate?
BMI > 35
Large fibroids
Hydraminos
What should women at high risk of pre-eclampsia be asked to do?
Take 75mg of aspirin daily from 12 weeks until the birth of the baby
Which women are at high risk of preeclampsia?
Women with any of;
- hypertensive disease during a previous pregnancy
- chronic kidney disease
- autoimmune disease such as systemic lupus erythematosis or antiphospholipid syndrome
- type 1 or type 2 diabetes
- chronic hypertension
Which women are at moderate risk of pre-eclampsia?
Women who have more than one of;
- first pregnancy
- age 40 or older
- pregnancy interval of more than 10 years
- BMI of 35kg/m2 or more at first visit
- family history of pre-eclampsia
- multiple pregnancy
