Blood Tests - Dr Ken Roper

KEN ROPER BSc(Med) MBBS FRANZCOG Obstetrics, Gynaecology, Colposcopy and Laparoscopic Surgery Conjoint Lecturer UNSW Provider Number 458915B 32/20‐24 Gibbs St
Miranda, NSW 2228
Ph: 9524 2129
31st January 2012 Blood Tests The following information is to be seen as a guide only and is not a substitute for consultation with a medical practitioner. Blood Group and Antibody Screen Your blood group is important to determine during pregnancy for two reasons. Firstly, blood transfusions may be required in approximately one in every 300 deliveries. Secondly, your blood group is also important if you are a Rhesus (D) negative blood type (approximately 15% of the Caucasian population) ‐ and if your partner is Rhesus (D) positive. In some pregnancies there are circumstances when blood can leave the baby’s circulation and enter the maternal circulation (such times as miscarriage, invasive procedures like chorionic villus sampling and amniocentesis, episodes of antepartum haemorrhage and during the course of delivery). Your immune system can recognise these fetal blood cells as foreign and attempt to destroy them by production of an antibody known as anti‐D. Thankfully this has become uncommon since the 1960’s because of technology whereby anti‐D can be extracted from donated blood which can then be administered in the occasions outlined above. There are also times when blood crosses passively from the baby’s circulation into your circulation and produce sensitization as described above. This sensitisation can be prevented by a prophylactic dose of anti‐D given at 28 and 34 weeks gestation. At the time of delivery a blood sample is taken from the umbilical cord to determine the baby’s blood group and if this is Rhesus (D) positive then a further dose of anti‐D is administered to the mother within 72 hours of birth. This will not be necessary if the baby is also Rhesus (D) negative. This information is not relevant for those pregnant women who are Rhesus (D) positive. Full Blood Count This test measures the levels of haemoglobin, an iron‐containing protein used to transport oxygen through the blood stream. If you have suffered particularly heavy periods or have had a number of pregnancies in fairly quick succession, haemoglobin levels can be low (anaemia). Other causes include blood loss and dietary deficiencies. Some vegetarians may also have low haemoglobin due to vitamin B12 deficiency. Ethnic groups from the Mediterranean region and South‐East Asia, can have an inheritable form of anaemia called thalassemia. This may be indicated by other parameters in your blood tests known as the mean corpuscular volume and mean corpuscular haemoglobin. Confirmation of this diagnosis is done with further blood tests, a haemoglobin electrophoretogram. If your partner has the same form of anaemia, your baby may have a more major and serious degree of thalassemia. Rubella Antibodies Most men and women born in the last 25 years will have been immunised against Rubella (German measles) during infancy. Prior to that time only teenage girls were immunised in secondary school. Rubella poses a serious risk to the unborn child of those pregnant women who are not immune to Rubella who then contract the disease during pregnancy. Rubella during pregnancy can result in damage to the developing baby by way of heart abnormalities, blindness, deafness and mental retardation. Fortunately, most people are aware of the need to be immunised to rubella prior to conception. If you are not immune it is important to avoid contact with potential carriers and to have a booster shot after delivery. Hepatitis B This is moderately uncommon infection in most communities and many people have been vaccinated before traveling overseas. However, certain populations have higher levels of carriage of hepatitis B. This virus can be transmitted to the baby during the course of pregnancy. For this reason, these babies can receive a concentrated dose of antibodies at the time of delivery known as hepatitis B hyperimmune‐globulin as well as immediate vaccination of the baby. If a baby develops hepatitis B it is often a surprisingly mild condition. However later in their life they can develop cirrhosis, chronic hepatitis and cancer of the liver. Some women who have hepatitis will have acute worsening of their disease during pregnancy and their liver function can deteriorate. Hepatitis C While uncommon, Hepatitis C can be acquired from administering drugs intravenously with unsterile needles, from unsterile tattooingand very uncommonly from receiving blood transfusions. Usually it is thought that a woman with Hepatitis C can deliver vaginally and breastfeed without any health impact on her baby. It is now believed that for women who have active Hepatitis C (as demonstrated by supplementary tests called Hepatitis C RNA) that Caesarean section may confer some protection against transmission of this virus to the baby. HIV HIV‐positive women can lower the risk of transmission to their babies by the use of anti‐retroviral drugs, avoiding breast‐
feeding and possible use of Caesarean sections. Syphilis Syphilis is a very uncommon disease. If it is not detected and left untreated it can have significant impact on the developing fetus. If discovered early enough it can be readily treated with antibiotics such as penicillin and with a significantly better outcome for the baby. Alpha Feto Protein This test is done at approximately 15‐18 weeks. An elevated level of Alpha Feto protein may indicate an increased risk of spina bifida. One Hour Glucose Challenge Test This test is done at 28 weeks gestation in all pregnancies. During pregnancy, a women’s need for insulin is approximately doubled by the end of the second trimester. While most women are able to produce this extra insulin from their pancreas, approximately 1‐2% won’t be able to ‐ particularly those older than 35, those with a family history of diabetes or a previously big baby. Undiagnosed diabetes can lead to a bigger baby (with the mechanical difficulties that may confer) or a baby with hypoglycaemia (low blood sugars). This test involves going to a pathology collection centre where you’ll be given a drink containing 50g of glucose, then you’ll need to stay there sitting quietly for 60 minutes before having a blood test for glucose level. You do not need to be fasting for this test, indeed it is best if you have had breakfast or lunch an hour or so beforehand as this glucose drink can be nauseating on an empty stomach. This result will be sent to Dr Roper. It should be <7.8. If it is >7.8 further tests are required or sometimes direct referral to an endocrinologist if it is very high.