Prenatal Screening Flashcards
Outline a prenatal screening Hx
- Maternal age
- Maternal disease - DM, epilepsy (meds)
- Previous obstetric hx
- Consanguinity
- Parent with known balanced translocation
- Exposure to: antiepileptics, warfarin, vit A (malformations)
- Infection: rubella (rash), CMA, parovirus, zika (travel)
List the maternal screening blood tests performed at booking?
Thalassaemia, sickle cell
Viral = syphilis, HIV, Hep B, rubella
Rh Ab
AFP (raised = open NTD, gastroschisis, cystic hygroma, congenital nephrosis, teratoma, infection, oesophageal atresia)
Trisomy 21 (downs), 18 (Edwards), 13 (Patau’s)
Outline down syndrome screening
Combined test
- Should be done between 11-13+6 weeks
- NT: in unable to obtain (foetal position, BMI) then serum screening by triple or quadruple test can be done between 15-20w (inhibin A, oestriol, HCG and AFP)
- Beta-HCG and PAPP-A (Preg Associated Plasma Protein-A)
- Low PAPP-A and high b-HCG: increased risk
In an OSCE, may need to explain what Down’s syndrome is: trisomy 21, genetic condition that causes certain physical characteristics and other complications such as congenital heart disease, vision and hearing problems, hypothyroidism, early onset dementia
What takes place during 1st trimester screening?
USS
- accurate dating
- twin
- fetal abnormalities
- measurements
- viability
- liquor vol
- placental location
- soft markers for aneuploidyrenal pelvic dilatation, choroid plexus cysts
- nuchal translucency measurement (increased in: Down’s, cystic hygroma, cardiac malformations, thoracic compressive syndromes-congenital diaphragmatic hernia, congenital infections)
Describe amniocentesis
15w, under direct US
15-20ml - culture of amniocytes, harvesting and banding
Indications:
- Assessment of fetal karyotype, maternal age, high risk for Down’s screening, USS findings, parental translocation, maternal request
- AFP and ACHE-assessment of possible congenital nephrosis
- Virology screen
- PPROM to rule out chorioamnionitis
- OD 450-haemolytic disease
Describe chorion villus sampling
After 10w, US guided, transabdominal/transcervical
Risk of miscarriage 1%
Indications:
- fetal karyotype where a rapid result is desirable
- genetic abnormalitiese.g.cystic fibrosis, thalassaemia major
- detection of viral DNA-maternal seroconversion-CMV
What methods are available for prenatal screening?
- Amniocentesis
- chorion villus sampling
- cordocentesis
- Fetoscopy
- Fetal skin biopsy
- Aspiration of fluid filled fetal cavities
What points are discussed and advised at a booking appt?
Discussion =
- Before 10w
- How the baby develops during pregnancy
- Exercise, including pelvic floor exercises
- Place of birth & pregnancy care pathway
- Breastfeeding, including workshops
- Participant-led antenatal classes
- Offer of all antenatal screening
- Mental health issues
Advice =
- Vitamins
- Should start folic acid (400mcg/d) 3m before conception (neural tube closes 6-8w)
- Only pasteurised milk, no soft ripened cheese, no pate, no raw eggs (mayo)
- No alcohol, smoking, drug-use
What examinations and routine tests take place at the booking appt?
Exam =
- CVS/Resp for foreign women (congenital heart defect may not have been identified)
- Genital examination (FGM)
- Height, weight - BMI (>30 higher risk for GDM, >35 high risk VTE/pre-eclampsia)
- Signs of domestic violence
Routine tests =
- FBC - anaemia
- HIV, HBV, syphilis
- ABO, Rh, any abnormal Ab
- Electrophoresis - thalassaemia, sickle cell
- Urinalysis - glycosuria, proteinuria, haematuria
At which points throughout the prenatal periods are blood tests performed and for what?
0-10w = sickle cell + thalassaemia
8-12w = ABO, Rh, Abs, syphilis, hep B, HIV
10-14w = early downs syndrome
28w = FBC, RBC alloAb, GTT if indicated (DM risk factors), Anti-D prophylaxis if Rh-ve
Prenatally when are USS performed?
11-14w = dating, viable, multiple, NTD (enencephaly - cranium not formed), nuchal translucency
18-22w = detailed anomaly
Growth + liquor vol every 3w from 26w (GROW pathway)
By 31w what should of been achieved in the maternity appts?
- Breastfeeding info
- Birth plan
- Recognision of active labour
- Care of new baby
- Vit K prophylaxis (raise levels to avoid bleed)
- Newborn screening tests
- Postnatal self care
- Awareness of baby blues, postnatal depression
- Risk assessment
- Low risk - choice of delivery place (home, midwifery led unit, consultant lead unit)
How should pregnancy be managed if >41w
> 42w fetal morbidity/mortality sharply raises
Should be offered membrane sweep - stripping the membrane from cervix - releasing prostaglandins inducing labour
IOL (if declined increase surveillance CTG + USS)
List the common post-natal health problems women need to be made aware of before labour
Depression
Mastitis (not being able to feed, LN swelling)
Endometritis
What methods can be used to date a pregnancy?
Neagele rule = used to find EDD. First date of LMP, take away 3 months, add 7 days, add 1 year
Dating USS: early USS between 10-13+6 weeks to determine gestational age and detect multiple pregnancies. Crown-rump length used (unless >84mm in which case head circumference used)
