Antenatal care Flashcards
How is pregnancy diagnosed
CF: secondary amenorrhoea, N+V (commonly within 2w of missing period, morning or any time), frequent micturition, excessive lassitude (for T1), breast tenderness (progesterone + water retention), maternal perception of fetal movements (~20w in first preg or 18w in other pregs), pica (wanting particular food)
Beta-hCG in urine/serum after ~10d post-conception
- False positives
- positive hCG without pregnancy - trophoblastic neoplasms
How is pregnancy dated?
- First day of the LMP - some idea of age but often inaccurate
- US in T1 to confirm gestational age
- EDD: 9m + 7d added to the first day of the LMP, or subtract 3m from the first day of the LMP and add 7d (Naegele’s rule) – not that accurate as women often dont know LMP, relies on a regular 28d cycle, assumes conception happened at point of ovulation
- 40% deliver within 5d of the EDD, and 2/3 within 10d so is a rough guide
- If normal cycle is >28d subtract/add appropriate number to the EDD
What is pseudocyesis?
Sx of pregnancy in a woman who isn’t pregnant - often due to fear/desire of pregnancy resulting in hypothalamic amenorrhoea
How many appointments should a woman with uncomplicated pregnancy have? What should be done at each?
- Nulliparous - 10
- Parous - 7
Check BP + urine for protein, and from 24w measure the symphysis-fundal height on growth charts
What is the booking appointment?
- Done before 12w
- Full history
- Maternal bloods: FBC, blood grouping + Rh, red cell alloantibodies, haemoglobinopathies (if at risk/at risk area), hep B, syphilis, rubella, HIV
- Explanation of screening tests
- Adv about diet, ensuring enough vitamin D, avoiding alcohol + certain foods
- General info about stages of pregnancy, antenatal classes
When is the combined test offered?
11-14w
When is the quadruple test offered?
15-20w, if they missed the combined one
What scans are routinely done for an uncomplicated pregnancy?
- Early pregnancy scan between 10-13w : confirm viability, singleton/multiple, estimate gestational age, detect major abnormalities like anencephaly (often combine with combined test as can check nuchal translucency)
- Fetal anomaly scan 18-20w
What vaccinations are recommended for pregnant women?
- Influenza
* Pertussis
What is tested at 28w?
FBC for anaemia
Red cell antibodies again
OGTT if they have RF
What is the rationale behind the NHS Fetal Anomaly Screening Programme?
Identify fetal problems in asymptomatic women, that may result in incompatibility with life/severe disability or benefit from early paed/antenatal treatment
Allows parents to be offered further tests, prepare for otherwise unexpected neonatal needs, have a TOP, manage birth in a specialist centre
They don’t have to have it
What does high risk screening result mean?
A greater than 1/150 chance of having the condition
What conditions does the FASP screen for?
- Chromosomal abnormalities - these are higher risk with maternal age. Down’s syndrome T21, Edward’s syndrome T18 and Patau’s syndrome T13
- Structural abnormalities - may benefit from antenatal treatment, or help with plans for delivery/postnatal, or indicate baby might die
What are the limitations to screening?
- False positives + false negatives
- Varying sensitivity + specificity
- Scan quality can be compromised by a high BMI, abdominal scars or a sub-optimal fetal position
What biochemical markers are used in screening?
- Beta-hCG: made by SCTB then placenta; high in T21, low in T18+13
- PAPP-A: made by placenta, if low in T1 is a/w T21+18+13
- Alpha fetoprotein: made by yolk sac+liver, high in NTD, low in T21 (in T2)
- Unconjugated estriol: made by placenta, low in T21 (in T2)
- Inhibin A: made by CL+placenta, high in T21 (in T2)
What is done in the combined test and what does it screen for?
- Maternal age
- Biochemistry: beta-hCG + PAPP-A
- Nuchal translucency measurement (thickness of SC fluid in fetal neck, if increased can indicate chromosomal abnormalities as collagen defect means tissue more elastic [may also be normal])
Screens for low/high risk of Down’s, Edward’s or Patau’s
What is the eligibility for the combined test?
11+1 to 14+1 W
CRL must be 45-84mm
Why is nuchal translucency not measured after 14w?
The fetal lymphatic system is more developed, so the excess fluid in the neck will drain away
What is the quadruple test?
- Done if miss T1 test/can’t obtain NT measurement
- Between 14+2 to 20+0 weeks
- Combines maternal age, AFP, beta-hCG, uE3 and inhibin-A
- Gives risk of Down’s syndrome only
When is fetal anomaly scan done and what does it look for?
- 18+0 to 20+6w, better to do it closer to 20w as structures more likely to develop
- Screens for 11 conditions that indicate baby may die/antenatal interventions/planning for delivery
- Looks at HC, AC, femur length, spine (vertebrae + skin covering), heart, kidneys, brain + face
- Only gives a side view of the fetus
- Conditions: anencephaly, spina bifida, cleft lip, CDH, gastroschisis, exomphalos, serious cardiac anomalies, renal agenesis, skeletal dysplasia, T18, T13
What is NIPT?
Non-invasive prenatal testing
Is a blood test done from 10w which measures cell-free fetal DNA in the mothers blood, if any DNA is over-represented for the chromosomes 21/18/13 it means a trisomy is higher risk
Not currently on NHS but has been recommended
Has a higher accuracy of diagnosis, as either positive (still need invasive test to confirm), negative (highly unlikely) or inconclusive (4% chance, when there’s not enough DNA)
What is done when a screening test picks up a higher risk pregnancy?
- Explain risks + benefits
- Appropriately trained person
- Anti-D prophylaxis if woman RhD-negative
- CVS or amnio
Chorionic villus sampling
- From 11-13+6w, biopsy the placental villi either through abdomen or cervix with US guidance
- Ind: high risk screen, prev child with chromosomal abnormality, carrier status, US evidence
- Accuracy slightly lower than amnio cos of mosaicism
- Pros: done earlier on so earlier management decisions
- Comps: 1% miscarriage, 10% PV bleed, pain, infection, rhesus sensitisation, mosaic result (normla+abnormal cells found so then need amnio)
Amniocentesis
- Done from 15w
- US guidance through abdo into amniotic sac, get fluid, send cells for karyotyping + PCR
- Ind: high risk on screening or a previously affected pregnancy
- Comps: miscarriage 1%, false negatives, infection, pain, Rh sensitisation, higher risk of club foot
