Foetal growth retardation
The most common reason for abnormally slow growth of the foetus (a ’small-for-dates’ foetus) is reduced blood flow to the placenta resulting in insufficient oxygen and nourishment reaching the foetus. This most often happens if the mother smokes and in women with pregnancy-induced hypertension. Less common reasons for slow foetal growth are other abnormalities of the placenta, congenital abnormalities of the foetus and maternal undernutrition. Identical twins share the same placenta, and one twin may grow more slowly because it receives less than its half-share of placental blood flow.
Foetal growth retardation is suspected when the uterus doesn’t enlarge at the expected rate and the mother’s weight gain is poor. It can be confirmed by ultrasound. Rest and observation in hospital are usually advised in an attempt to improve the placental blood flow. Delivery is induced when the obstetrician, in consultation with the parents and a pediatrician, decides that the baby would have a better chance in the nursery than in the uterus. The baby usually catches up quickly after birth.
Gestational diabetes
Sometimes diabetes appears for the first time during pregnancy, though usually not until towards the end of the second trimester. When this happens, blood sugar can usually be controlled by diet alone, but more frequent antenatal checkups will be advised. Pregnancy-induced diabetes disappears after delivery.
Rhesus iso-immunisation
The Rhesus (Rh) factor is an antigen found on the surface of red blood cells. It was first identified in the rhesus monkey, hence its name. Over 85 per cent of people have this factor in their blood and are said to be Rh-positive. People who don’t have the Rh antigen on their red blood cells are Rh-negative. If Rh-positive blood enters the circulation of an Rh-negative person (for instance by transfusion), an antibody to the RH factor develops because the RH factor is recognized by the immune system as foreign. This antibody destroys Rh-positive red cells.
The Rh factor is very important in pregnancy. If a woman with Rh-negative blood carries a foetus with Rh-positive blood, some of the foetus’s red blood cells may cross into the mother’s blood and stimulate the development of anti-Rh antibody in the mother’s serum. This is Rhesus iso-immunisation. In the same or a later pregnancy these antibodies can cross to the baby and if the baby is Rh-positive, can destroy some of its red cells, resulting in anaemia and jaundice.
Bleeding from the foetus to the mother can happen at any time during pregnancy, but is most likely in spontaneous or induced abortion, ectopic pregnancy, antepartum haemorrhage or during delivery.
Mothers with Rh-negative blood have their blood examined at the beginning of each pregnancy and at about 28 and 36 weeks. If antibodies are detected, it means that some foetal red cells have crossed to the mother and that the foetus may be anaemic. The degree of foetal anaemia can be measured by examining the amniotic fluid (by amniocentesis). If the foetus is mildly anaemic, labour may be induced around 38 weeks. If anaemia is severe, delivery may need to be earlier. In very severe cases, blood transfusion to the foetus in the uterus may be undertaken before delivery. The baby is checked immediately after birth to see if there has been so destruction of the baby’s red cells that change transfusion is needed, in which baby’s damaged blood is replaced with negative blood.
If jaundice is present, the baby nursed in a crib under a light that break down bilirubin, the pigment broken-down red cells that causes jaundice. If bilirubin is allowed to reach high levels in the baby’s blood, it can lead to brain damage.
Rh iso-immunisation used to cause many stillbirths and much severe illness in newborns. Since the introduction of anti-D gamma globulin (which acts anti-Rh antibody and destroys Rh-positive red cells) in the 1960s, these proplems have become rare. All women with negative blood are now given anti-D immediately after any pregnancy in the hope of destroying any foetal red cells that may have crossed from the foetus before Rh iso-immunisation can develop.
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