Placenta | Placental insufficiency
Placental insufficiency (or uteroplacental vascular insufficiency) is a complication of pregnancy in which the placenta is unable to deliver an adequate supply of nutrients and oxygen and, thus, cannot fully support the developing fetus.
- Placental insufficiency occurs when the placenta either does not develop properly or because it has been damaged.
- Placental insufficiency can mean a reduction in maternal blood supply and/or the failure of the maternal blood supply to increase or adapt appropriately to the needs of the fetus by mid-pregnancy.
- Placental insufficiency can result in pregnancy complications, including fetal growth restriction (FGR) and pre-eclampsia.
Placental insufficiency can be assessed by the following placental function tests: umbilical artery Doppler (fetal blood flow to the placenta), maternal biochemistry, placental ultrasound, and uterine artery Doppler (mother’s blood flow to the placenta).
Once placental insufficiency has been diagnosed, the next steps depend on when in pregnancy the diagnosis is made. Management of the condition is also dependent upon additional tests and the unique characteristics of each patient.
Factors considered during management of complicated pregnancies are maternal medical and obstetric history, weight, ethnicity, and blood pressure.
By offering women a program of serial testing at 12, 16 and 20 weeks, the diagnosis of placental insufficiency is typically made before any ill effects on the mother (such as pre-eclampsia) or the developing fetus (intrauterine or fetal growth restriction (IUGR/FGR))are evident. Rarely, one or both may be seen before 20 weeks, and, if so, the outcome is often poor, unfortunately. Most women and fetuses who exhibit multiple test abnormalities before 24 weeks gestation may be healthy at that point. If they show early signs of pre-eclampsia or fetal growth restriction, this increases their risk of preterm delivery (<32 weeks) to approximately 30%.
How placental insufficiency will be managed depends on when in pregnancy it is diagnosed. If placental insufficiency is diagnosed before the developing fetus is viable (<24 weeks), women should expect:
- Coordinated care between their referring obstetrician/family doctor/midwife, and the specialized clinic. Since the risk of preterm delivery is high, this permits a smooth transfer of care as needed;
- Education about pre-eclampsia, so that the mother can self-monitor her blood pressure at home: this prevents a late diagnosis when severe uncontrolled hypertension may result in early birth and can be a risk to the mother and/or her developing fetus;
- A plan of fetal monitoring using ultrasound so that FGR is recognized and monitored carefully;
- An integration of this plan with regular visits (standard prenatal care).
If placental insufficiency is diagnosed after the developing fetus is viable (>24 weeks), the disease can either remain sub-clinical (not be expressed as FGR and/or pre-eclampsia), or one or more of several issues develop:
- Excess maternal weight gain, leg swelling, headaches (signs of pre-eclampsia);
- The mother’s stomach measures small or the fetus is not moving very well (signs of FGR);
- The fetus has not moved for two days and no fetal heart beat can be found in the Clinic (signs of stillbirth);
- Some vaginal bleeding and/or contractions develop (signs of preterm labour with placental separation, or abruption).
The following steps will be taken if any of the above-mentioned conditions are noted:
- If a degree of either pre-eclampsia or FGR develops, then clinic visit frequency will be increased from every 2 weeks to weekly, then to twice a week and ultimately to hospital admission for daily monitoring;
- If a concern about the need for delivery arises before 32 weeks, then the mother will be offered a course of steroids (2 intra-muscular [thigh] injections). These steroids diffuse across the placenta to strengthen the developing lungs, helping the fetus prepare in the event that an early birth is indicated;
- If pre-eclampsia and/or FGR are more severe and are likely to require delivery before 32 weeks, then a high-risk obstetrician or maternal-fetal medicine (MFM) specialist takes over to provide intensive outpatient or inpatient care.
Referral Information (for physicians)
All patients with suspected placental insufficiency should be referred to a tertiary care centre, such as Mount Sinai Hospital, for evaluation. Antenatal care and monitoring will be shared with the referring physician as appropriate.