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38 Cards in this Set
- Front
- Back
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When can the gestational sac be visualised?
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From as early as 4 -5 weeks gestation.
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When can the embryo be observed and measured?
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From 5 - 6 weeks gestation.
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When can a visible heartbeat be recorded?
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From 6 weeks.
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What is the ultrasound result for a missed miscarriage?
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A foetus but no heart beat.
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What is the ultrasound result for a blighted ovum?
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A gestational sac is present but empty.
A blighted ovum, or anembryonic pregnancy, happens when a fertilized egg attaches itself to the uterine wall, but the embryo does not develop. Cells develop to form the pregnancy sac, but not the embryo itself. It will naturally miscarry. |
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What is the ultrasound result for an ectopic pregnancy?
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Positive pregnancy test PLUS
No gestation sac within the uterus Adnexal mass present Fluid in the pouch of Douglas |
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Up to which point is the CRL used?
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13 weeks + 6 days.
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Up to which point is the HC preferred?
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14 weeks to 20 weeks.
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What four parameters are used to estimate foetal growth later in pregnancy? (20 weeks plus)
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HC
AC - abdominal circumference FL - femur length BPD - biparietal diameter |
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What is the expected asymettry for a FGR pregnancy?
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Larger HC compared to AC because of brain-sparing effect.
I.e. in the lack of nutrients, there is preferential sending of nutrients to the brain, so it is proportionately bigger. |
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What is the expected asymmetry in a diabetic pregnancy?
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AC > HC. Because the effects of insulin on foetal liver and fat sores makes the abdomen larger.
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What is a monochorionic twin pregnancy?
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Twins who share a placenta.
Increased risk of pregnancy complications and perinatal mortality compared to dichorionic twins. |
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What is a dichorionic twin pregnancy?
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Twins who have different placentas.
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Why do monochorionic twins look different to dichorionic twins on ultrasound?
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The dividing membrane in monochorionic twins is formed by two layers of amnion, but in dichorionic twin is formed by two layers of chorion and two of amnion. They therefore have thicker membranes. The membrane looks thicker on US. Also get the "twin peak" or "lambda" sign.
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What are some structural anomalies that can be diagnosed on ultrasound?
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Spina bifida
hydrocephalus achondroplasia exomphalos and gastroschisis cleft lip and palate congenital cardiac abnormalities |
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What are some first trimester 'soft' markers for chromosomal abnormalities?
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Absence of foetal nasal bone
Increased foetal nuchal translucency |
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When is it customary to look at the placental location?
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20 week scans identify women with low lying placenta.
However, the lower uterine segment has not yet formed (uterus will form into three segments), so most low-lying placentas will pmigrate upwards as the lower segment stretches in the second and third trimesters. |
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What are the measurements of amniotic fluid?
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1. Maximum vertical pool. < 2cm oligohydramnios. > 8cm polyhydramnios.
2. Amniotic fluid index. Divides the uterus into quadrants and a vertical measurement is taken of the deepest cord free pool in each and the results summated. < 10cm bad, < 5cm oligohydramnios, > 25cm polyhydramnios. |
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What are some causes of oligohydramnios?
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Renal agenesis.
Posterior urethral valves. FGR because blood is redirected away from kidneys to vital structures. |
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What are some causes of polyhydramnios?
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Anything that causes difficulty of the foetus to swallow, e.g. anencephaly, oesophageal or duodenal atresia.
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What is the CTG?
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Cardiotocograph. Continuous tracing of foetal heart rate and uterine activity.
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What is the normal baseline foetal heart rate?
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110 - 150 beats per minute.
May be slightly lower in older mums. 160 bpm is acceptable at term. |
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What can cause foetal tachycardia?
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Maternal or foetal infection.
Acute foetal hypoxia. Foetal anaemia. |
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What is baseline variability?
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Longer term fluctuations in heart rate occurring between two to six times per minute.
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What is abnormal baseline variability?
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Less than 10 bpm.
(Reduction during foetal sleep for 20 - 30 minutes is normal, but should be preceded and followed by good variability.) |
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What are foetal heart rate accelerations?
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These are increases in the baseline foetal heart rate of at least 15 bpm, lasting for at least 15 seconds. They are positive signs of foetal health.
The presence of two or more accelerations on a 20-30 min CTG is considered good and reactive. |
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What are foetal heart decelerations?
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Reductions of 15 bpm or more lasting for 15 seconds.
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What can decelerations be indicative of?
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Foetal hypoxia or umbilical cord compression.
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What are the parameters in the biophysical profile?
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CTG: reactive = 2, fewer than 2 accels in 40 minutes = 0.
Foetal breathing movements: >30 sec in 30 min = 2, fewer = 0. Foteal body movements: >3 movements in 3 minutes = 2, < 3 = 0. Foetal tone: one episode of limb flexion = 2, none = 0. Amniotic fluid volume: largest pocket > 1cm = 2, < 1cm = 0 |
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What is the significance of the scores in a biophysical profile.
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0, 2, 4 all bad, do delivery.
6 = equivocal, probs retest. 8, 10 = good. |
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What is the US of the umbilical artery used for?
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To assess placental health.
Provides information on feto-placental blood flow and placental resistance. |
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What normally happens to diastolic flow in the umbilical artery throughout gestation?
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Diastolic flow increases as placental resistance falls throughout gestation.
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What is the significance of absent or reversed end-diastolic flow in the umbilical artery?
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Strong correlation with foetal distress and intrauterine death.
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If the resistance index in the umbilical artery rises above the 95th percentile of the normal graph, what does this mean?
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Faulty perfusion of the placenta, may result in hypoxia.
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What are the negative associations with a diastolic notch in the umbilical artery waveform?
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Preeclampsia
FGR Maternal abruption |
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What does chorionic villus sampling sample?
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Foetal trophoblast cells in the mesenchyme of the villi.
Methods: 1. Needle through abdominal wall. 2. Catheter or biopsy forceps through cervix into placenta. |
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What does amniocentesis sample?
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Amniotic fluid contains amniocytes and fibroblasts shed from foetal membranes, skin and the genitourinary tract.
Amniocentesis takes a 15 - 20 mL sample of fluid which contains these cells. |
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What does cordocentesis sample?
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Can be performed around 20 weeks.
Performed when foetal blood or rapid karyotype is needed. Needle is passed under US guidance into the umbilical cord at the point where it inserts into the placenta Risk of miscarriage 2 to 5 %. |
