Antenatal Care and Screening in Pregnancy Flashcards
Outline the objectives of antenatal care.
- Detect and manage pre-existing maternal disorders that may affect pregnancy outcome
- Prevent or detect and manage maternal complications of pregnancy
- Prevent or detect and manage fetal complications of pregnancy
- Detect congenital fetal problems if requested by parents
- Plan with the mother the circumstances of birth to ensure maximum safety for the mother and baby and the maximum parental satisfaction
- Provide advice regarding lifestyle
- Offer reproductive choice
Outline the main principles of any screening test.
- Highly sensitive.
- Highly specific.
- Have a 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.
How do we assess the robustness of a screening test?
By assessing sensitivity and specificity.
Sensitivity =
True positive / (positive + false negative
Specificity =
True negative / (negative + false positive )
Outline the sensitivity and false positive rate of Down’s Syndrome screening in the 1st trimester.
A sensitivity of 90% for a false positive rate of 5%.
What should history cover in a women’s booking visit?
- Menstrual.
- Medical.
- Obstetric.
- Family.
- Social.
What should examination cover in a women’s booking visit?
- Height.
- Weight.
- BP.
- CVS.
- Abdomen.
Other than scanning, how can due date be estimated?
With Naegele’s Rule which predicts estimated due date based on the onset of the woman’s LMP.
- Simply add on nine months and seven days to arrive at the due date – 280 days.
What investigations should be carried out at booking visit?
Bloods for:
- Hb. (look for iron deficiency anaemia)
- ABO; Rhesus.
- Syphilis; HIV; Hep B + C.
Urinalysis: MSSU C+S.
Ultrasound.
Why is an ultrasound used at the booking visit?
- To confirm viability.
- Singleton or multiple pregnancy?
- Estimate gestational age – explain most accurate time/method to establish EDD.
- Detect major structural anomalies that may be identified in early pregnancy.
- Offer DSS.
What is the function of the yolk sac?
Supports the pregnancy as it develops up until the placenta forms.
Dichorionic twins on US shows what sign?
Lambda
What circumference do you measure to give the babies due date?
Head circumference
In follow-up visits, what aspect of the history are we interested in?
- Physical and mental health.
* Foetal movements.
What aspects are covered in examination during follow-up visits?
- BP and urinalysis.
- Symphysis-fundal height.
- Lie and presentation. (if baby is transverse at 36weeks, start to worry as there is a danger of cord prolapse and malposition)
- engagement of presenting part.
- Fetal heart auscultation.
What are the objectives for screening for foetal anomaly with US?
- Reduction in perinatal mortality and morbidity.
- Potential for in-utero treatment.
- Identification of conditions amenable to neonatal surgery.
In how many pregnancies, do major structural abnormalities occur?
2-3%
The majority of major structural abnormalities occur in ___ risk women
LOW
All pregnant women should be offered the 18+0 to 20+6 weeks foetal anomaly scan
True
At how many weeks gestation, should all women be offered a foetal anomaly scan?
18+0 to 20+6
What is placenta praaevia?
When the placenta is low-lying in the womb and covers all or part of the entrance (the cervix).
Why does placenta praevia not cause a problem in most women?
The womb usually grows upwards, and the placenta moves with it so that it is in a normal position before birth.
If an earlier US scan (between 18+6 and 20+6) showed that your placenta extends over the cervix, what should be done?
You should be offered another abdominal scan at 32 weeks.
If you are shown to have placenta praevia and the other abdominal scan at 32 weeks confirms this, what should be done?
A vaginal scan
In the first trimester, what factors contribute to the risk assessment for Down’s syndrome in a baby?
- Measuring of skin thickness behind the fetal neck using ultrasound – Nuchal thickness; NT.
- Combined with HCG and PAPP-A.
When is nuchal thickness measured?
At 11-13+6 weeks.
Describe what nuchal thickness is considered normal.
A nuchal thickness of <3.5mm, when the CRL (crown rump length) is between 45 and 84mm.
In the 2nd semester, what factors contribute to the Down’s Syndrome risk assessment.
- Blood sample at 15-20weeks.
* Assay of HCG and AFP.
How is personal risk evaluated? (in both 1st and 2nd trimester for Down’s)
By incorporating the above-mentioned measurements/results with maternal age and gestation.
What is regarded as ‘high risk’ for Down’s? What does this require?
> 1:250 risk.
- requires further investigation e.g. amniocentesis
Outline the Down’s risk assessment.
- Requires accurate pregnancy dating.
- Requires detailed counselling.
- ‘Low risk’ doesn’t exclude Down’s Syndrome.
Who gets 2nd trimester screening for Aneuploidy?
Those women who miss first trimester screening.
or
Those women in whom CUBS in unsuccessful.
What factors are looked at in 2nd trimester screening for aneuploidy?
Maternal Age + Biochemical Markers:
- Alpha-fetoprotein (AFP)
- human Chorionic Gonadotrophin (hCG)
- unconjugated oestradiol (UE3)
- inhibin A
What is Cell Free Foetal DNA Testing/Non-Invasive Prenatal Testing (NIPT)?
A test that can identify pregnant women who are at higher risk of having a baby with certain genetic and chromosomal conditions, such as Down’s syndrome (also known as Trisomy 21), Edwards’ syndrome (Trisomy 18) and Patau’s syndrome (Trisomy 13).
When is amniocentesis usually performed?
After 15 weeks
What is the rate of miscarriage associated with amniocentesis?
1%
When is chorionic villus sampling usually performed?
After 12 weeks.
What is the rate of miscarriage associated with chorionic villus sampling?
2%
Only high risk women are screened for sickle cell anaemia and thalassemia
TRUE
Sickle cell anaemia and thalassemia are both autosomal _________
Recessive
Name 3 deficiencies which may lead to maternal anaemia.
- Iron deficiency.
- Folate deficiency.
- B12 deficiency.
When is maternal anaemia screened for?
At booking, and 28 weeks.
What should you aim for in maternal anaemia?
To optimise Hb prior to birth.
What % of the population are rhesus -ve?
15%
Why does rhesus disease take a while to develop after pregnancy?
IgG antibodies take a while to develop, so it’s not until the following pregnancy where there’s a problem.
When should all women have their blood group and antibody status be determined?
At booking + 28 weeks gestation
It is important to assess mental health in mothers !! What questions should be asked at every appointment?
- 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 feelings persistent?
- Do you feel you are getting worse?
What should you assess risk of gestational diabetes using?
Risk factors in a healthy population.
At the booking appt, what risk factors for gestational diabetes should be determined?
- BMI above 30 kg/m2
- Previous macrosomic baby weighing 4.5 kg or above
- Previous gestational diabetes
- Family history of diabetes (first degree relative with diabetes)
- Minority ethnic family origin with a high prevalence of diabetes.
Who should be offered testing for gestational diabetes?
A woman with any single risk factor
What should be used to test for gestational diabetes in women with risk factors?
The 2-hour 75g oral glucose tolerance test (OGTT).
What are the diagnostic parameters for gestational diabetes?
Fasting plasma glucose level of 5.6mmol/litre or above.
OR
2-hour plasma glucose level of 7.8mmol/litre or above.
What is recommended as it improves prediction of a small for gestational age (SGA) neonate?
Serial measurement of symphysis fundal height (SFH) is recommended at each antenatal appointment from 24 weeks of pregnancy.
What should SFH (symphyseal fundal height) be plotted on? Why?
A customized chart rather than a population – this may improve P predication of a SGA neonate.
Who should be referred for US measurement of foetal size?
Women with a single SFH which plots below the 10th centile, or serial measurements which demonstrate slow or static growth by crossing centiles.
Who should be referred for serial assessment of foetal size using ultrasound?
Women in whom measurement of SFH is inaccurate (e.g. BMI >35, large fibroids, hydramnios).
What should you advise women at high risk of pre-eclampsia to take?
75mg of aspirin daily from 12 weeks until the birth of the baby.
List women who are at high risk of pre-eclampsia.
- 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.
What factors would indicate moderate risk of PET?
- first pregnancy
- age 40 years or older
- pregnancy interval of more than 10 years
- body mass index (BMI) of 35 kg/m2 or more at first visit
- family history of pre-eclampsia
- multiple pregnancy.
What does urinalysis look for in pregnancy?
- UTI.
- Asymptomatic bacteriuria.
- PET (proteinuria)
- Diabetes.
