SGA & FGR

SGA & FGR EDD = 40 weeks from LMP (Naglers rule – add 9 months & subtract 7 days) For dating scan – crown rump length (8-10 weeks) or Biparietal diameter (16-20 weeks) Low birth weight = any baby < 2.5kg Small for gestational age = any baby < 10th centile (or 5th or 3rd) Fetal growth restriction (or IUGR) = failure to reach genetic growth potential. The baby falls away from its centiles. Measurements must be minimum 2 weeks apart Maternal Factors Maternal nutrition Oxygen (poor outcome if high altitude, cyanotic heart disease Drugs & smoking (tobacco, heroin, cocaine, alcohol) Chronic disease (renal, respiratory, SLE etc) Placental factors Adequate invasion by trophoblast Adequate vascular function (thromboxane à vasoconstriction & platelet aggregation) Fetal factors Genetic (maternal genes more important than paternal) Chromosomal (trisomy & triploidy à reduced growth) Fetal anomaly (structural or due to infection) IUGR The causes can be Intrinsic: malformations, including chromosomal abnormalities (5-10%) viral infections (2%). Extrinsic: UPVD cyanotic heart disease maternal malnutrition if severe ‘toxins' - smoking, alcohol, cocaine, medications (e.g. atenolol) idiopathic (30%). Risk factors include Short stature Previous small baby Low maternal weight (<45 kg) and BMI Poor weight gain Multiple pregnancy Smoking, alcohol and other ‘toxins' (see above) Raised AFP Two patterns of IUGR are recognized: Symmetrical/early: usually due to intrinsic problems (e.g. congenital abnormality, viral infection). On US, both HC and AC measurements fall away from expected growth trajectories Asymmetrical/late: usually due to extrinsic problems (e.g. pre-eclampsia, multiple pregnancy). On US, AC values fall away from expected growth trajectories but HC growth is mostly maintained Prematurity Prematurity – gestation less that 37 weeks Very Preterm – less than 32 completed weeks Preterm labour – regular uterine contractions, effacement & dilatation after 20 weeks and before 37 weeks Preterm Prelabour ROM – ROM before 37 weeks and before onset of labour Low birth weight - < 2500g Very low birth weight < 1500g Extremely low birth weight < 1000g Risk factors for preterm delivery Uterine abnormality Antepartum haemorrhage Intrauterine infection Bleeding in 1st / 2nd trimester Placenta praevia Prelabour ROM FGR Multiple pregnancy Preeclampsia Pschological stress Fetal abnomaly Polyhydramnios Maternal UTI or other infection Management Confirm diagnosis (assess cervix, look for fibronectin, only digital PV if no ROM) Assess maternal & fetal well-being Give steroids if delivery before 34 weeks is likely (betamethasone / dexamethasone) caution if DM Inhibition of preterm labour Beta-sympathomimetics – ritodrine & salbutamol à inhibits actin/myosin interaction required for contraction. Can à tachycardia, visual disturbance, skin flushing, n & v, hyperkalaemia & hypergylcaemia Oxytocin antagonist (atosiban) – similar to ritodrine but fewer side effects Cox inhibitors – indometacin. Main risk is to fetus (closure of ductus) & reduced UO Calcium channel blockers (nifedipine). Reduces myometrial contractility. Contraindications to tocolysis Significant vaginal bleeding Pre-eclampsia or other maternal condition requiring immediate delivery Fetal growth restriction Fetal death Lethal congenital anomaly Chorioamnionitis Significant fetal distress Preterm Prelabout ROM If very early – risk of lung hypoplasia & skeletal anomaly Diagnosis observe pool in posterior fornix Will turn nitrazine sticks orange à black Oligohydramnios on scan NB: vaginal examination contraindicated bec risk of infection à chorioamnionitis Management – if labour not established then monitor regularly. If less than 34 weeks give steroids Fetal Haemolytic Disease Most important group is RhD Mother must be Rh - , with fetus Rh +. When blood mixes mum develops Ab. First response is IgM which does not cross. On 2nd exposure IgG produced à crosses placenta Effect on fetus Haemolysis à anaemia (unless sufficient haemopoiesis) à fetal hypoxia & acidosis à hepatic & cardiac dysfunction à oedema, ascites & effusions (pericardial & pleural) = HYDROPS FETALIS Post delivery haemolysis à jaundice High risk events for mixing Miscarriage & ectopic pregnancy Invasive procedures (eg amnio) External cephalic version Abdominal trauma Antepartum haemorrhage Labour (esp 3rd stage) Prevention – all Rh – mothers are given anti D during pregnancy Indications for increased prophylaxis ectopic preg, TOP, miscarriage requiring surgery, amniocentesis/CVS, threatened miscarriage, antepartum haemorrhage, external cephalic version, delivery At birth Perform Rh group on fetal cord blood. If Rh + à Kleihauer test on maternal blood à estimate of volume transfer à calculate AntiD required