Fetal abnormalities can be detected
through antenatal checks during antenatal
visits. Depending on mother's family
history, medical background, previous
pregnancies and age, your doctor may
recommend a range of tests deemed
suitable.
Routine
tests :
At your initial visit, your caregiver
will take a blood sample and feel
your abdomen; at this and subsequent
visits your blood pressure (BP)
and urine will be assessed. Most
often, hospitals and clinics schedule
appointments every 4 weeks until
week 28, then it becomes every 2
weeks until week 36 and then weekly.
Blood and
Urine tests
Blood test is taken to check
blood group, hemoglobin levels (to
check for anemia) and immunity to
rubella (a postnatal vaccination
will be given if you are not immune).
This blood test also checks for
Aids, syphilis, diabetes, hepatitis
and rhesus status. The blood pressure
reading taken at your first visit
will be used as a barometer to measure
subsequent readings. It is normal
for your BP to be higher in the
later part of pregnancy. Urine is
checked for ketones, protein and
glucose.
The presence of
1. ketones affects the transportation
of oxygen in the blood
2. protein indicates preeclampsia
or some infection
Ultrasound scanning
The scan is pain-free
and there is no risk of miscarriage.
It is routinely done at 16-18 weeks.
High pitched sound waves are reflected
back off the baby and replicated
electronically as an image on a
screen. It confirms dates and multiple
pregnancies, detects abnormalities
and placental position.
Special
tests
Most of these
tests are optional; you are not
obliged to have them. Your decision
should be based on sound judgment;
you must understand what is being
offered and why, and also the risks
involved. Finally you should consider
the possibility of the results being
positive and whether or not to terminate
the pregnancy. Support and counseling
services are available in case of
such an outcome.
Transvaginal
scan
Carried out from 5-6 weeks, a probe
is inserted into the vagina giving
a clear view of the developing baby.
Advantages
-
results
are instant
Disadvantages
-
baby is
exposed to high frequency sound
CVS (chrorionic
villus sampling)
Detects chromosomal and genetic disorders
such as Downs's syndrome and sickle
cell anemia. A tube is inserted into
the uterus at 8-12 weeks and cells
are taken from placental tissue surrounding
the embryo.
Advantages
-
very accurate
and preliminary results within 48
hours
Disadvantages
-
risk of
miscarriage (roughly 1 in 100)
Nuchal
test
Non-invasive ultrasound scan carried
out at 12 weeks to detect chromosomal
disorders. 'Nuchal' means neck: the
scan checks for abnormal thickness
in the fold at the back of the baby's
neck. When combined with a blood test,
this test is 80-90% accurate in predicting
Down's syndrome.
Advantages
-
non invasive
and no risk of miscarriage
Disadvantages
-
none
AFP (alpha-fetoprotein
test)
Blood test that checks blood protein
levels and neurological problems such
as spina bifida or hydrocephalus.
It is carried out at weeks 15-18.
Accuracy is not good: high and low
levels of alpha-fetoprotein can be
found in women carrying healthy fetuses
and those who are very nauseous. Results
take about 10 days.
Advantages
-
non invasive
with no side effects
Disadvantages
-
50% accuracy,
false positive rate of 5-10%
Amniocentesis
Sample of amniotic fluid taken under
local anesthesia through the abdominal
wall at 16-18 weeks to test for disorders
such as Down's syndrome. Results in
2-3 weeks
Advantages
-
accuracy
of 90%; reveals baby's gender which
is important with some disorders
Disadvantages
-
risk of
miscarriage (less than 1 in 100);
discomfort, side effects such as bleeding,
infection; screens few defects
Triple/Quadruple/Leeds/Bart's
tests
Combination of blood tests to assess
risk of chromosomal defects or problems
such as anencephaly (absence of a
brain) or spina bifida.
Advantages
-
no risk
of miscarriage
Disadvantages
-
accuracy
between 60 - 80%
