Serology: Testing for Hepatitis, HIV and syphilis allows monitoring or treatment to occur and may alter labour and delivery plans to minimise the risk of vertical transmission to the baby. Women who are rubella negative require no treatment but are advised to receive a vaccination after they have delivered.
Blood Group and Antibodies: Checking this ensures that blood can be cross matched if there is haemorrhage in the pregnancy. Women who are Rhesus negative can sometimes develop antibodies to a current or future pregnancy that can cause the baby to become anaemic. Rarely this can be life threatening to the baby, and therefore all Rhesus negative women are advised to have an anti-D antibody injection at 28 and 34 weeks and at any time there is a risk of internal bleeding (for example after any vaginal bleeding in pregnancy or after any injury to the abdomen). By giving an external source of anti-D antibodies, it prevents women from developing their own antibodies to the baby’s blood. Less commonly, women who are Rhesus positive can develop antibodies which can require additional monitoring.
Blood Count and Ferritin: Red blood cells in the body are important for carrying oxygen to the tissues of the mother and baby. The molecule in these cells that is responsible for this is called Haemoglobin. Haemoglobin is a protein that requires iron in order to be made by the body. Having low levels of haemoglobin is a condition known as anaemia which has been associated with growth problems in babies and can cause tiredness and breathlessness in the mother. In pregnancy, the commonest cause of low Haemoglobin is iron deficiency. The iron stores in the blood are carried by another protein called Ferritin. For this reason we check Haemoglobin levels at least twice in the pregnancy. Ferritin levels are often checked but are less important that the actual Haemoglobin level. If your haemoglobin or iron levels are low, you may be advised to take additional iron supplements. Note that a low Ferritin level does not make you unwell, but it increases the chance that you will become anaemic.
Vitamin D: Very low levels of vitamin D in the mother are associated in bone development problems in childhood. In addition, there is some early evidence that low Vit D may be associated with other developmental problems and in the baby, multiple sclerosis in later life, and possibly pre-eclampsia in the mother. It is important to be aware that these associations have been identified from early studies and the exact link between vitamin D and these conditions is still being investigated. Many women have lower than normal levels and so it is reasonable for all women to consider taking a vitamin D supplement in their pregnancy. An alternative approach is to check the blood vitamin D level at booking and at around 28 weeks, although there are no large international studies that have yet shown that treating low vitamin D aggressively makes any difference to babies’ health. More research is required for the benefits to be absolutely proven, but it seems reasonable and safe to take these supplements.
Midstream urine: Urinary tract infections are more common in pregnancy and so a routine specimen is obtained at the beginning of the pregnancy. Excluding urine infections has been shown to prevent pre-term labour.
Urine protein tests: These will be done if you are at risk of pre-eclampsia or if you have high blood pressure.
These are used to initially confirm a live (viable) baby and later to exclude developmental problems in the baby. The most important of these is the anatomy scan performed around 20 weeks. This is when the organs are large enough to see but the baby is small enough for the key structures to fit on the screen.
Approximately 1% of pregnancies will have a major abnormality. Please note that the purpose of the scan is to check for these problems and this should be considered when deciding who to bring with you for your scans. In particular, young children can be distressed if they are present when problems are identified.
It is also important to know that not all physical abnormalities will be detected by ultrasound. Genetic or mental developmental abnormalities and may not be identified.
Ultrasound is also used to determine the position of the placenta. A low placenta at 20 weeks does not necessarily mean it will remain low. Usually a repeat scan is arranged for 32 weeks to review the location. A placenta that covers the cervix is known as a placenta praevia. If this is identified then you will be advised to avoid strenuous exercise and intercourse and to report any bleeding immediately. If it remains low close to your due date, a Caesarean section may be required.
In addition to ‘formal’ ultrasounds performed by sonographers or specialist obstetric sonologists, informal ultrasounds may be used in my rooms to confirm the baby’s heart beat, the position of the baby, or the fluid volume around the baby for example. It is important to be aware that these scans are done to provide specific information and do not provide the same detail as the specialist anatomy scan performed at 20 weeks.
Approximately 20% of women carry a bacteria in the vagina known as Group B Streptococcus (GBS). This occurs naturally and is harmless before and during the pregnancy. If GBS is present at the time of a vaginal birth, there is a small risk that it can be acquired by the baby and there is then a small risk of the baby developing an infection in the skin but occasionally and more seriously in the brain (meningitis). Although severe outcomes are rare, they can be prevented by treating women at risk with Penicillin (or other antibiotics if allergic) during labour.
One option is to perform a vaginal swab at 36 weeks and to treat women who carry the bacteria. The other option is only to treat women who are at risk of their babies developing an infection (such as premature babies, prolonged ruptured membranes, or fever in labour). I recommend the routine swab at 36 weeks, but am happy to discuss this if you have other preferences.
Down syndrome screening is an option for all women to consider. Down (or Down’s) syndrome is the commonest major chromosomal abnormality and affects approximately 1:1000 pregnancies. It is more common in babies born to older women although an affected pregnancy can occur in women of any age. Tests for Down’s syndrome are divided into screening tests and diagnostic tests.
Screening tests: The three tests currently available are the non-invasive prenatal screening test (NIPT), the combined first trimester screening tests (FTS) performed at 11 to 13 weeks and 6 days,and the second trimester blood test known as serum screening. The first of these is the most accurate. Screening tests do not have any physical risk to the pregnancy, but are not 100% accurate. This means they will not detect all affected pregnancies and will only provide an estimate of the risk of the baby being affected.
NIPT: This new test measures tiny amounts of the baby's DNA circulating in the mother's blood. This is highly accurate (over 99%) but more expensive than the others. If the result is positive, a diagnostic test such as CVS or amnio is recommended for confirmation.
For all screening tests, ivf you have a result reported as low risk, no further action is required. If you are reported as high risk, you will be given the option of a diagnostic test. These are only usually performed on high risk women as they have a risk of complications:
Diagnostic tests: There are two invasive tests performed on higher risk women. Chorionic Villus Sampling (CVS) or Amniocentesis (Amnio). These may be done if you have had a high risk screening test, but may also be considered if you are known to have a genetic condition in the family, or have had a previous pregnancy affected by a genetic problem.
Both tests involve taking a sample of tissue or fluid from around the baby. Both tests are almost 100% accurate. This tissue is then analysed to check the genetic makeup (chromosomes) of the baby. There is a fast test known as fluorescent in-situ hybridisation (FISH) which is available after 24hrs, and a longer test where tissue is cultured which can take 10-14 days. The problem is that both these tests can cause pregnancy loss through internal bleeding, ruptured membranes, infection, or by setting off contractions, which is why they are reserved for higher risk situations.
Before you decide to have the screening tests, you should be aware:
- Of what Down syndrome is.
- That you understand what the screening test is, including what is involved.
- That screening tests are safe but are not 100% accurate. They provide an estimate of the odds of having an affected baby.
- That a high risk screening test does not necessarily mean the baby is affected, just that the odds of this are higher than the cutoff.
- That if you have a high risk screening result you will be offered a more accurate diagnostic test.
- That diagnostic tests provide a more certain answer but carry a risk of miscarriage.
- You should consider how you would manage the result of a high risk screening test or a pregnancy affected by Down syndrome.
I would suggest you discuss this list with your partner or family before electing to have the test. Request forms for screening can be completed by myself or by your GP.
Further information is on the Victorian Clinical Genetics Services Website www.vcgs.org.au under Patients and Families / Screening / Maternal Serum Screening
Cystic Fibrosis (CF) is one of the commonest genetic medical conditions. It affects 1:2500 pregnancies. Most babies are born to parents who do not know they carry the gene for the condition. Approximately 1:25 adults carry the gene for this, but if both parents carry it, they have a 1:4 chance that any pregnancy will be affected. It mainly affects the lungs, causing sometimes major breathing difficulties, but also affect the intestinal system and shortens the person’s lifespan. All babies are tested with this condition a few days after birth with the heel prick test.
A test is available to find out if the parents are carriers of the gene. This is done by taking a blood sample to obtain some cells, then analysing these for the CF gene. The test takes about a week. If one parent is found to be a carrier, the other parent is tested, and if both are carriers, genetic counselling and testing of the baby by amniocentesis or CVS (described above) can be considered. Please let me know if you wish to be tested.
Your GP may have already arranged a number of investigations for you. The general purpose of all antenatal investigations is to test the mother or baby for conditions that can be modified, monitored or treated in order to improve outcomes (such as diabetes screening), or where knowledge of certain conditions can be used to plan management or liaise with other specialists.