Antenatal care & screening Flashcards
What are the phsyiological changes associated with normal pregnancy in the mother?
1) Morning sickness
2) Cardiac output increases by 30-50% (increase in SV and HR)
3) Blood pressure drops in 2nd trimester (decreased vascular resistance, blood viscosity and reduced sensitivity to angiotensin) and returns to normal in 3rd trimester
4) Increased urine output (renal plasma flow increases 25-50% and GFR increases by 50%, urea and creatinine decrease)
5) UTI (increase in urinary stasis)
6) Anaemia as a result of dilution (plasma volume increases by 50% but RBC’s only increase by 25% so results in anaemia)
7) Respiratory (increased RR, plasma pH, tidal volume and O2 consumption increases by 20%)
8) GI (gastric emptying slows, cardiac sphincter relaes and GI motility reduced due to increased progesterone and reduced motilin)
What is pre-pregnancy counselling and what is involved?
1) General health measures:
- Improve diet
- Optimise BMI
- Reduce alcohol
2) Smoking cessation device
3) Folic Acid (400microgram)
4) Confirm Immunity to Rubella
5) Psychiatric health
6) Stop/change unsuitable drugs (anti-epileptic - sodium valproate)
7) Advice about maternal medical problems
What is the procedure and implications of the antenatal examination?
Aims to identify problems with mother, fetus or social problems
1) Routine enquiry - feeling well, feeling fetal movements (after 20 weeks)
2) Blood pressure - detect hypertension, urinalysis
3) Abdominal palpation - assess fundal height, estimate size of baby & liquour volume
4) Determine fetal presentation and listen to fetal heart
What is the basis of screening for fetal abnormalities?
- Offered to woman but not compulsory
- Appropriate counselling prior to screening is important
- Allows conditions to be detected early in a symptomless population
What screening tests are offered to woman and what are their limitations?
Infection:
Hepatitis B
Syphilis
HIV
UTI’s
Rubella
Anaemia & Isoimmunisation:
Iron deficiency anaemia
Isoimmunisation - Rhesus disease, Anti-c, Anti-kell
Structural anomalies:
1st visit scan - viable pregnancy, multiple pregnancy, down’s syndrome screening
Detailed anomaly scan - structural review of baby
What is the detection rate for downs syndrome?
90%
What is checked during the 1st trimester screening?
1) Maternal risk factors
2) Serum Beta-human chorionic gonadotrophin (B-hCG)
3) Pregnancy associated plasma protein A (PAPP-A)
4) Fetal Nuchal Translucency (NT)
What are nuchal translucency measurements used for and how do NT measurements relate to maternal age and incidence of chromosomal abnormalities?
Used in the detection of fetal downs syndrome
NT increases in thickness with increasing maternal age
The likelihood of incidence of chromosomal and other abnormalities is related to the size of the NT
What happens if maternal history and NT measurements indicate a high risk of Down’s syndrome (> 1 in 150)?
- CVS (Chorionic Vilus Sampling)
- Amniocentesis (small amount of amniotic fluid collected)
- Non-invasive prenatal testing
What are the potential risks of having invasive diagnostic procedures such as CVS and Amniocentesis?
Miscarriage risk of 1-2%
What Neural Tube defects are screened for during 1st trimester USS?
Anencephaly
Spina bifida
Is a 2nd trimester USS better at detecting major structural anomalies or chromosomal abnormalities?
Major structural abnormalities
What is the 1st USS sign of pregnancy?
Thickening of the lining of the womb
Once a fetal pole has been identified, what important measurement of fetal development can then be made?
Crown Rump length - lenght from one end of the embryo to the other end.
How does the CRL correlate to the gestational age?
CRL correlates closely with Gestational age
How is the estimated due date calculated?
EDD = date of last period + 7 days + 9 months
OR
CRL using USS
What information can be gathered from the 1st trimester USS?
1 - Gestational age and EDD
2 - Miscarriage
3 - Multiple pregnancies
4 - Ectopic pregnancies
What is the overall incidence rate for Downs syndrome?
1 in 700
What is involved in the CUB test which detects chromosomal abnormalities?
Nuchal Translucency together with:
- hCG and PAPP-A blood levels
How effective is the CUB screening test?
85% of abnormalities are detected
What defects can be detected during the 2nd trimester USS?
Neural Tube defects
What protein is a marker of Neural tube defects?
Alpha-feto protein
A level of > 2 multiples of the median normal value for alpha-feto protein is considered abnormal
What is the overall aim of the 2nd trimester USS?
Identify structural abnormalities
What is the overall aim of the 3rd trimester fetal assessment?
- Ensure fetal wellbeing
What are the identifiable features on USS between weeks 1-4.5?
Fluid-filled intrauterine getsational sac
What can be identified on the USS between 2-5 weeks gestation?
2 - 5 weeks = Yolk sac appears
What features can be identified on USS between 3-5.5 weeks gestation
Tiny fetal pole is visible
What features can be seen on USS between 4-6 weeks?
First fetal heart pulsation may be visible
What is the name of the tests that are initially carried out detect the risk of downs syndrome?
- The CUB (Combined Ultrasound & Biochemical)
At what stage of gestation is the CUB screening test carried out?
Between 11 & 14 weeks
Does the CUB tests definitively say if a baby will be born down syndrome?
Screening for downs syndrome ONLY provides a risk of their baby being affected
What is the cut-off for being at high risk of the fetus having down syndrome?
1 in 150
What is involved in the CUB test?
USS - Check for Nuchal Translucency
Blood test - Check for beta-hCG and PAPP-A
What other factors are taken into account when computing the risk of the fetus having down syndrome?
Maternal age
Family history of chromosomal abnormalities
What happens next if a mother is identified as being high risk of having a baby with down syndrome?
1 - Amniocentesis
2 - Chorionic Villus Sampling
3 - Non-invasive prenatal testing
What screening is performed in 2nd trimester for NTD’s?
Maternal serum is tested for alpha fetoprotein
- > 2.0MoM = high risk and further investigation required
What proportion of NTD’s will be detected from 2nd trimester USS?
>90%
