Perinatal Medicine Flashcards
1
Q
Perinatal medicine
‘Terms’
A
- Stillbirth – fetus born with no signs of life ≥24 weeks of pregnancy
- Perinatal mortality rate – stillbirths + deaths within the first week per 1000 live births and stillbirths
- Neonatal mortality rate – deaths of liveborn infants within the first 4 weeks after birth per 1000 live births
- Neonate – infant ≤28 days old
- Preterm – gestation <37 weeks of pregnancy
- Term – 37–41 weeks of pregnancy
- Post-term – gestation ≥42 weeks of pregnancy
- Low birthweight (LBW) – <2500 g
- Very low birthweight (VLBW) – <1500 g
- Extremely low birthweight (ELBW) – <1000 g
- Small for gestational age – birthweight <10th centile for gestational age
- Large for gestational age – birthweight >90th centile for gestational age.
2
Q
Pre-pregnancy care
Couples planning to have a baby often ask what they should do to optimise their chances of having a healthy child. They can be informed that for the mother
A
- Smoking reduces birthweight, which may be of critical importance if born preterm
- Pre-pregnancy folic acid supplements reduce the risk of neural tube defects in the fetus
- Any long-term conditions, such as diabetes and epilepsy, must be reviewed and management
- Certain medications such as retinoids, warfarin and sodium valproate must be avoided
- Alcohol ingestion and drug abuse (opiates, cocaine) may damage the fetus
- Congenital rubella is preventable by maternal immunisation
- Exposure to toxoplasmosis minimised by avoiding eating undercooked meat and wearing gloves when handling cat litter
- Listeria infection can be acquired from eating unpasteurised dairy products
- Eating liver during pregnancy is best avoided as it contains a high concentration of vitamin A
3
Q
Pre-pregnancy care
Pregnancies at increased risk of fetal abnormality include those in which:
A
- the mother is older (if she is >35 years old, the risk of Down syndrome is >1 in 380), although screening is now available for all mothers
- there is previous congenital abnormality
- there is a family history of an inherited disorder
- the parents are identified as carriers of an autosomal recessive disorder, e.g. thalassaemia
- a parent carries a chromosomal rearrangement
- parents are close blood relatives.
4
Q
Antenatal diagnosis
Maternal Blood
A
Screening tests for antenatal diagnosis
Maternal blood:
- Blood group and antibodies – for rhesus and other red cell incompatibilities
- Hepatitis B
- Syphilis
- Rubella
- HIV infection
- Neural tube defects – raised maternal serum alphafetoprotein (MSAFP) with spina bifida or anencephaly, but ultrasound alone increasingly used
- Down syndrome – risk estimate calculated from age, biochemical markers combined with ultrasound screening for nuchal translucency (back of neck). Aim is to detect >75% with <3% false-positive rate. If high risk, fetal chromosome analysis
5
Q
Screening tests for antenatal diagnosis
Ultrasound screening
A
- Gestational age – can be estimated reliably if early in pregnancy
- Multiple pregnancies – can be identified
- Structural malformation – 50–70% of major congenital malformations can be detected. If a significant abnormality is suspected, a more detailed scan by a specialist is indicated
- Fetal growth – can be monitored by serial measurement of abdominal circumference, head circumference and femur length
- Amniotic fluid volume – oligohydramnios may result from reduced fetal urine production (because of dysplastic or absent kidneys or obstructive uropathy), from prolonged rupture of the membranes or associated with severe intrauterine growth restriction. It may cause pulmonary hypoplasia and limb and facial deformities from pressure on the fetus (Potter syndrome)
- Polyhydramnios – is associated with maternal diabetes and structural gastrointestinal abnormalities, e.g. atresia in the fetus
6
Q
Screening tests for antenatal diagnosis
Main structural malformations and other lesions detectable by ultrasound
A
CNS
- Anencephaly – always detected
- Spina bifida
- Hydrocephalus, microcephaly, encephalocele
Cardiac
- About 50% of severe malformations detected on ‘routine’ screening, over 90% at specialist centres
Intrathoracica
- Diaphragmatic hernia, congenital cystadenomatoid lung malformation (CCAM)
- Oesophageal atresia
Genitourinary
- Dysplastic or cystic kidneys
- Obstructive disorders of kidneys or urinary tract (hydronephrosis, distended bladder)
Skeletal
- Skeletal dysplasias, e.g. achondroplasia and limb reduction deformities
Hydrops
- Oedema of the skin, pleural effusions and ascites
Chromosomal
- Down syndrome – suspected from thickened back of neck (nuchal translucency), duodenal atresia or an atrioventricular canal defect of the heart. Other chromosomal disorders – from identifying multiple abnormalities
7
Q
Fetal medicine
A
- Glucocorticoid therapy before preterm delivery accelerates lung maturity and surfactant production
- Glucocorticoid therapy before preterm delivery accelerates lung maturity and surfactant production
- Rhesus isoimmunisation. Severely affected fetuses become anaemic and may develop hydrops fetalis, with oedema and ascites
- Perinatal isoimmune thrombocytopenia. This condition is analogous to rhesus isoimmunisation but involves maternal antiplatelet antibodies crossing the placenta
8
Q
Fetal surgery
A
- Catheter shunts inserted under ultrasound guidance. This is to drain fetal pleural effusions (pleuro-amniotic shunts), often from a chylothorax (lymphatic fluid) or congenital cystic adenomatous malformation of the lung
- Laser therapy to ablate placental anastomoses which lead to the twin–twin transfusion syndrome (TTTS)
- Intrauterine shunting for obstruction to urinary outflow as with posterior urethral valves
- Dilatation of stenotic heart valves via a transabdominal catheter inserted under ultrasound guidance into the fetal heart
- Endotracheal balloon occlusion for congenital diaphragmatic hernia
- Surgical correction by hysterotomy. This is when the uterus is opened at 22–24 weeks’ gestation
