Fetal Welfare
·
Clinical assessment. Key issue is serial measurement:
o Mother:
§ Blood pressure
§ Maternal weight
§ Test urine from 20 weeks for albumin (ie proteinuria) and glucose
§ Oedema
§ Check Hb and Rh antibodies (eg at 28 weeks) and do glucose challenge
o Baby:
§ Symphyseal-fundal height (SFH)
·
Indicator of weeks gestation –
roughly 1 cm per week. Drops a bit at
term
· Measure from top of pubic bone to top of uterus
·
NB – can just palpate uterus on
the abdomen at 12 weeks. At 20 weeks up
to umbilicus
§ Lie and presentation from 32 weeks
§ Fetal heart: use Doppler (mum can hear it too). Normal is 110/120 to 160 bpm.
§ Fetal movements (from 19 – 20 weeks in primips, earlier in multips): if
no movement then asleep or sick. Awake foetuses are active
o OSCI tips:
§ First introduce yourself, wash hands, get sheet to cover legs
§ Explain what you‟re going to do
§ BP in sitting/semi-reclined position
§ Look for oedema – especially pre-tibial. Enquire about hands and face
§ Inspect abdomen for shape, size, scars, striae and linear nigra, symmetry. Is
the baby transverse or longitudinal
§ Measure fundal height
§ Find poles to determine lie
§ Where is the back: Feel laterally (brace hand other side), then walk
hands across.
§ Ask what position it was on last scan and ask where she‟s feeling
movements
§ Pawlicks grip above symphasis then both hands to measure descent. Watch face for pain
·
20-week morphology scan. Fetal risk 0%. Operator dependent. Assesses:
o Fetal number, lie and cardiac activity
o Fetal anatomy: CNS, CVS, GIT, GU, musculoskeletal anomalies (eg neural
tube)
o Gestational age (BPD, head/abdomen circumference ratio, femur length)
o Amount of amniotic fluid (poly or oligo-hydramnios)
o Placental location (low lying?)
o Pelvic pathology: fibroids, cysts, etc
o Give reassurance: ¯parental anxiety
·
Further investigations: Most have
high false positives Þ interpret in light of clinical picture
o Cardiotocography (CTG - fetal heart rate monitoring). See Topic: Cardiotocography (CTG) in Labour
o Doppler ultrasound of blood flow in umbilical artery (not routine)
o Ultrasound scan: fetal size (biparietal diameter, abdominal
circumference, femur length), amniotic fluid estimation, assess fetal breathing
(eg ¯ in hypoxia)
o Biophysical Profile: Only if high risk. Score of fetal heart rate,
breathing movements, fetal movement, fetal tone and amniotic fluid volume. Not
often done in NZ
·
Reasons for prenatal diagnosis:
o If an abnormality is detected, termination may be considered
o Knowledge of an abnormality may give time to adjust/prepare
· For Down syndrome see Topic: Down Syndrome
·
Screening tests (higher false
+ive, especially if low risk women) – used to modify existing risks:
o Fetal nuchal translucency (= nuchal fold): at 10 - 14 weeks, measure
soft tissue thickening on posterior neck, normal < ~ 3 mm. Thickness
(adjusted for maternal and fetal age) associated with chromosomal
abnormalities. Combine with other risk factors (eg age). Fetal risk 0%
o Maternal serum screening (triple blood test – now quadruple test): at 15
– 17 weeks, measures AFP, HCG and free and bound oestriol. Serum levels,
maternal age and gestational age are used to calculate the risk of neural tube
defects and chromosomal abnormalities ® classification as high risk (eg
1:50 for Down) or low risk (1:2700 for Down). Fetal risk 0%
·
Diagnostic tests (higher false
–ive):
o Indications: positive results from screening, previous child affected by
a congenital/genetic disorder or family history, maternal age > 35, maternal
condition or medication with possible effect on baby
o All introduce risk of Rh isoimmunisation Þ give
anti-D afterwards if RH -ive
o Chorionic villous sampling (CVS): from 10 weeks, trans-abdominal or trans-cervical. Karyotyped in 2 days, gene/enzyme analysis takes
longer, 1 – 3% miscarriage. Can‟t detect neural tube defects. Complicated by
maternal contamination or fetal mosaicism (~ 0.5%). If mosaic, skin cells in
fetus closer to the babies karyotype than placental cells
o Amniocentesis: from 14 weeks (10 – 13 weeks ® 5% miscarriage). Culture amniotic cells for 2 – 3 weeks ® detects
chromosomal abnormalities and neural tube defects. Risk 0.5% miscarriage. Gold
standard but late. Difficult if anterior placenta or oligohydramnios
o Cordocentesis (Percutaneous umbilical blood sampling): from 18 weeks. Miscarriage rate
of 1 – 3%. Rapid karyotyping – good for detection of fetal blood
disorders and infection (eg rubella)
·
= Intra-uterine Growth
Retardation (IUGR). Don‟t use this term
in front of parents!
· = Failure to achieve full growth potential. Not quite the same as small for gestational age (< 10th percentile)
·
Causes of ¯SFH:
descent, changes in lie, IUGR, oligohydramnios
·
Common cause of perinatal death
(along with prematurity and congenital malformation)
·
Associated with NIDDM,
hypertension, heart and thyroid disease in later life
·
Asymmetrical:
o Chronic placental insufficiency – head preferentially protected
o Occurs in maternal illness/smoking, multiple pregnancy, idiopathic
o ® ¯Abdominal circumference cf the head, ¯amniotic fluid
·
Symmetrical: Everything smaller
due to eg congenital malformation, chromosome abnormalities, infections or
toxins
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