The appearance of the Placenta is very important throughout pregnancy. Magnetic resonance imaging (MRI) may be indicated if there is a suspicion of an abnormality.
An abnormally increased placental thickness is associated with increased risk of placental insufficiencies such as fetal macrosomia, fetal hydrops, TORCH infections or maternal conditions such as diabetes or anaemia.
An abnormally decreased placental thickness is associated with pre-eclampsia or Intra-uterine growth restriction (IUGR).
1. Placenta Previa
This is when the placenta partially or completely covers the cervix, which is the outlet of the uterus. It may result in vaginal bleeding early in pregnancy as the uterus grows and may also resolve as this happens.
• Grade I: low lying placenta - placenta lies in the lower uterine segment, but its lower edge does not abut the internal cervical os.
• Grade II: marginal praevia - placental tissue reaches the margin of the internal cervical os, but does not cover it.
• Grade III: partial praevia - placenta partially covers the internal cervical os.
• Grade IV: complete praevia - placenta completely covers the internal cervical os.
2. Placental Abruption
This occurs when the placenta tears away from the uterine wall either partially or entirely before delivery. It may cause pain and vaginal bleeding and may result in a reduced supply of oxygen and nutrients to the baby and therefore prompt delivery will be necessary.
• Retroplacental Haematoma;
• Intra-Placental Anechoic Areas;
• Separation and Rounding of The Placental Edge;
• Thickening of The Placenta: Often to Over 5.5 Cm;
• Thickening of The Retroplacental Myometrium;
• Disruption in Retroplacental Circulation;
• Blood in The Fetal Stomach.
3. Placenta Accreta
This is when the placental blood vessels grow too deeply into the wall of the uterus. It may result in vaginal bleeding in the last trimester and severe blood loss after delivery.
• Marked thinning or loss of the retroplacental hypoechoic zone;
• Interruption of the hyperechoic border between the uterine serosa and bladder;
• Presence of mass-like tissue with echogenicity like that of the placenta;
• Visualization of prominent vessels or lakes within the placenta or myometrium.
4. Retained Increta
The placental villi extend beyond the confines of the endometrium and invades the myometrium.
5. Placenta Percreta
There is a transmural extension of placental tissue across the myometrium with serosal breach.
• Protrusion of placental tissue beyond the outer confines of the uterine myometrium;
• Increased vascularity between serosa and adjacent structures such as the bladder.