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Chapter: Medicine Study Notes : Reproductive and Obstetrics

Fetal Welfare

Assessment of Fetal Growth and Well-Being, Prenatal diagnosis, Fetal Growth Restriction (FGR).

Fetal Welfare


Assessment of Fetal Growth and Well-Being


·        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


Prenatal diagnosis


·        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)


Fetal Growth Restriction (FGR)


·        = 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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Medicine Study Notes : Reproductive and Obstetrics : Fetal Welfare |

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