placental insufficiency

see also:

• Obstetrics
• fetal growth restriction (FGR / SGA / IUGR)

• placental insufficiency is the failure of the placenta to deliver sufficient nutrients to the fetus during pregnancy
• this does not include complete placental abruption which is a separate condition

• placental insufficiency may cause:
  • oligohydramnios
  • fetal growth restriction (FGR / SGA / IUGR) - placental insufficiency is the most frequent cause of asymmetric IUGR but may be present in babies with normal fetal growth (“latent placental insufficiency”)
    • symmetric IUGR affects weight and length equally and indicates early onset FGR
    • asymmetric IUGR affects weight mainly (have a low Ponderal index) and indicates late onset FGR
  • fetal metabolic and endocrine changes including:
    • fetal hypoglycaemia and triggers epigenetic responses in the fetus that are otherwise activated in times of chronic food shortage and this may result in obesity and type 2 diabetes in later life
    • fetal hypoxia and secondary polycythemia, delayed CNS development, decline in fetal activity and later fetal breathing ceases
    • fetal hypercapnia and lactic acidosis
    • raised fetal serum glucagon, adrenaline, noradrenaline levels, eventually causing peripheral glycogenolysis and mobilization of fetal hepatic glycogen stores resulting in reduced ability to tolerate hypoxic stress of labour
    • impaired immune response leading to higher infection susceptibility of infant after delivery
    • reduced umbilical venous volume flow with fetal blood flow selectively diverted to myocardium, adrenal glands and, particularly, the brain causing elevation of pulmonary vascular resistance and increased right ventricular afterload.
      • shunting of blood from the splanchnic circulation results in reduced renal blood flow, reduced glomerular filtration rate and hence less liquor and thus oligohydramnios
      • Eventually the rising CVP and decreased cardiac output may ultimately lead to tricuspid insufficiency, fetal heart rate decelerations and fetal demise.
  • decreased fetal movements (DFM or RFM)
  • miscarriage or stillbirth / FDIU
  • pre-eclampsia and eclampsia

• 75% of cases are not detected until a still birth occurs or a baby is born with fetal growth restriction (FGR / SGA / IUGR)
• FGR affects 5-10% of babies and accounts for 30-50% of stillbirths
• the risk for stillbirth is greatest after 37 wks gestation
• longitudinal growth assessments with intervals <3 weeks are prone to result in a large proportion of false positives making it problematic in late pregnancy

• see fetal growth restriction (FGR / SGA / IUGR)
• cease smoking advice
• biochemical screening tests for Trisomy 21 as a test of placental insufficiency
• first trimester ultrasound for dating and nuchal translucency;
• First and second trimester screening tests for aneuploidy maybe useful tests of placental function. If two screening test results are abnormal, health care providers should be aware that the fetus is at increased risk of preterm intrauterine growth restriction and associated stillbirth
• biometric USS at 18wks
• uterine artery Doppler at 19 to 23 weeks if biochemical markers are abnormal
• maternal–fetal medicine consultation at 18-20wks if at risk
• serial fundal height estimation
• routine 3rd trimester ultrasound scan performs better than selective scans based on risk factors
• ultrasound examination for estimated fetal weight and amniotic fluid volume should be considered after 26 weeks if the symphysis-fundal height measurement in centimetres deviates by 3 or more from the gestational age in weeks or there is a plateau in symphysis-fundal height
• a 36wk USS is better at detecting SGA than a 32wk USS
• Umbilical artery Doppler should be performed in all fetuses with an estimated fetal weight or an abdominal circumference < 10th percentile
  • In pregnancies affected by intrauterine growth restriction, umbilical artery Doppler studies after 24 weeks may prompt intervention that reduces perinatal mortality and severe perinatal morbidity due to intrauterine growth restriction
  • Doppler assessment of the umbilical artery (UA) in early SGA is useful in detecting placental insufficiency but this is not useful in late SGA when Doppler assessment of middle cerebral artery (MCA) flow provides a better indicator together with abnormal cerebroplacental ratio (CPR) which is the ratio between MCA and UA pulsatility index (PI). SGA babies with abnormal CPR have a 10-fold increased risk of adverse outcome.

• optimise maternal health
• maternal screening for infections
• Low-dose aspirin should be recommended to women with a previous history of placental insufficiency syndromes including intrauterine growth restriction and preeclampsia. It should be initiated between 12 and 16 weeks’ gestation and continued until 36 weeks
• Low-dose aspirin should also be recommended to women with two or more current risk factors in pregnancy including, but not limited to, pre-gestational hypertension, obesity, maternal age > 40 years, history of use of artificial reproductive technology, pre-gestational diabetes mellitus (type I or II), multiple gestation, previous history of placental abruption, and previous history of placental infarction. It should be initiated between 12 and 16 weeks’ gestation and continued until 36 weeks
• When intrauterine growth restriction is diagnosed, surveillance should be initiated.
  • If pre-viable (< 500 g ± < 24 weeks):
    • offer counselling by multi-disciplinary health care team regarding fetal monitoring and obstetrical intervention until viability.
  • If viable (> 500 g and > 24 weeks):
    • conduct initial ultrasound assessment: EFW, AFV, umbilical Doppler; in third trimester (~ 26 weeks) consider weekly BPP and growth every 2 weeks.
  • Serial ultrasound estimation of fetal weight (every 2 weeks), along with umbilical artery Doppler studies should be initiated.
  • If available, a placental assessment and other Doppler studies such as middle cerebral artery, umbilical vein, and ductus venosis can be performed.
  • Increased frequency of surveillance may be required
• If fetal growth starts to plateau, amniotic fluid index starts to decline, or fetal tone or gross movements are diminished or absent, then more intensive surveillance (e.g., 2 to 3 times per week) or admission to hospital and delivery planning is required
• Abnormal umbilical cord Doppler (e.g., absent or reversed end-diastolic flow) in the presence of intrauterine growth restriction is an ominous finding that requires intervention and possible delivery.
• Maternal administration of corticosteroids is indicated if there is a significant possibility of delivery at < 34 weeks’ gestation, as administration may positively affect umbilical Doppler studies.
• delivery of SGA babies at risk of placental insufficiency (with abnormal CPR) after 37–38 weeks
• consider early deliver of normal growth babies with abnormal CPR