ANTENATAL SCREENING TEST

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PRENATAL TESTING

PRENATAL TESTING, THE BENEFIT OF EARLY ANTENATAL CARE

The prenatal period or antenatal period is the time from fertilization just until before birth. Prenatal testing are screening and confirmatory tests that are carried out during the prenatal period on the mother or product of conception (placenta, amniotic fluid) for the possible presence of a disease condition either on the mother or baby. This screening and confirmatory tests are called prenatal tests.

Generally, these tests are done early in pregnancy. They might be repeated in the course of the pregnancy. Hence, the importance of early antenatal care booking to benefit from these screening tests where possible. The availability of some prenatal test depends on the available laws in the country and the availability of diagnostic skill, technology and approved treatment protocol. Even where it is available, it is not mandatory.

So, based on your history and examination findings, your healthcare provider may recommend some antenatal testing for chromosomal abnormalities. In some countries, it is part of the routine testing for all pregnant women in early pregnancy. After counselling on what the conditions are, availability of screening or confirmatory test and the possible treatment available. These tests might be ordered. It is optional and you can choose not to participate.

PRINCIPLES OF PRENATAL TESTING

A screening test help categorize the patient into a low risk or high risk group. Further testing is carried out on those classified as high risk. There should be a balance between the potential benefits of a screening test to the harm it might cause in an otherwise healthy pregnancy. Hence, the principles of prenatal testing as reported by Wilson and Jungner (1968).

  • The health condition screened for must be an important health problem.
  • There should be an accepted treatment for pregnant women and babies identify with the disease condition.
  • There should be available facility and skill for diagnosis and treatment.
  • There should be a recognizable dormant or early symptomatic stage.
  •  The natural history of the condition which includes it development from a dormant to a declared disease, should be adequately understood.
  • There should be a suitable test or examination.
  •  The test should be acceptable to the population.
  •  There should be an agreed policy on whom to treat as a patient.
  • The cost of diagnosis and treatment of patients should be economically balanced in relation to possible expenditure on medical care as a whole.
  •  Case‐finding should be a continuing process and not a ‘once and for all’ project.

PRENATAL TESTING FOR GENETIC ABNORMALITIES

Genes are a portion of the chromosome involve in the transfer of traits from parents to their children. Abnormalities in the number or structure of a chromosome can result in diverse disease conditions. Common amongst them include Down’s syndrome, Edward syndrome, Patau syndrome, Turner’s syndromes and a lot of other disease conditions. Nature has a way of taking care of things that it only allows the fittest to survive most of the time.

Thus, explaining the reason why a lot of these pregnancies abort spontaneously. Sometimes, before the woman even realizes she is pregnant. Some of these pregnancies with genetic abnormalities continue and the babies are delivered alive. Most of them have intellectual disability and cannot live an independent life thus, a burden to both the family and the healthcare system.

Hence, in countries where abortion is legal, such pregnancies are terminated if the couple do not want to continue with the pregnancy.

THE SCREENING TESTS

First trimester combined screening involves the use of ultrasound scan and maternal blood to screen for chromosomal abnormalities. A fetal nuchal translucency of ≥ 3.5mm as seen on scan with a reduce pregnancy associated plasma protein -A(PAPP-A) and increased free beta human chorionic gonadotropins (B-HCG) in maternal blood is associated with Down’s syndrome.

However, an increased fetal nuchal translucency with reduced PAPPA-A and B-HCG is associated with Edward, patau’s and Turner’s syndromes. Non-invasive prenatal testing using cell free fetal DNA obtain from the maternal blood can also be used for screening for Down’s syndrome.

THE CONFIRMATORY TEST

 After a positive screen, a confirmatory test using cytogenetic studies can be carried out such as karyotyping. Karyotype which could be rapid or full karyotype, study the number and structure of the chromosome. This test reveals abnormalities depending on whether it is the full karyotype or rapid karyotype. The full karyotype is a comprehensive study and takes about 2 weeks to get the result.

Moreover, the rapid karyotype is limited to abnormalities in a few chromosomes implicated in Down’s, Edward, patau syndrome and also abnormality of the sex chromosomes. It takes about 48hours to get the result. Samples for karyotyping can be gotten via amniocentesis or chorionic villus sampling. These procedures are recommended early in the first trimester, about 11weeks of pregnancy for chorionic villus sampling and 15weeks for amniocentesis.

Just like amniocentesis, chorionic villus sampling is associated with some complications such as perforation of the intestine, bleeding and pregnancy loss. There is no need looking for something you do not want to act upon and get yourself worked up throughout the pregnancy period. If you are a pro-lifer, prenatal testing for chromosomal abnormalities might not be for you.

ANTENATAL CARE

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ANTENATAL CARE

ANTENATAL CARE
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Before the advent of antenatal care, pregnancy in the early centuries used to be a very dreaded period in the life of a woman. Though, that did not stop women from getting pregnant. You must have heard people say a pregnant woman has one leg in heaven and the other on earth, this is due to high mortality from pregnancy. Due to advancement in science and technology through research, this pregnancy associated deaths have been reduced to a minimum.

Antenatal care has played a significant role in this reduction in the rate of maternal mortality. The aim of antenatal care is to have a good pregnancy outcome that is, a healthy mother and baby. This is achieved through the provision of information on the changes in pregnancy, education on diet and lifestyle modifications, screening for and treatment of pregnancy related complications, treatment of underlying disease conditions that might impact negatively on the pregnancy outcome.

To achieve this aim, you have to be actively involved in your care by following the advice of your healthcare provider and taking your required medications. Please do not be deceived that you have experience from your previous pregnancies and as such, will not need antenatal care or will only book for antenatal care when the pregnancy is far advanced or even near delivery time. Note that no two pregnancies are the same.

ANTENATAL CARE; THE BOOKING CLINIC

This is where your antenatal care journey begins. Some hospital might even give you a tour of their facility. The tour is basically to areas where you will be using various services in the course of the pregnancy. This might include a tour to the antenatal ward, labour room, labour theatre, ultrasound scan service area, blood bank and the laboratory.

At the booking clinic you will be required to provide information on the following; your last normal menses, previous deliveries, medical and surgical history, medication and allergy history, family history, social history including that of domestic violence and female genital mutilation where applicable. If you have had a preconception counselling and care before getting pregnant then, some of these histories will already be in your medical record. The date of the last menses will be used to calculate the age of the pregnancy and the expected date of delivery. Other histories obtained will help categorize the pregnancy as a high or low risk pregnancy and this will also determine the frequency of the antenatal care visit. Clinical examination will also be carried out which will include vital signs, weight and height measurement, systemic examination, a clinical breasts examination to ensure there are no breasts diseases that needs urgent treatment, and also to check that the nipples are fine and will not pose a challenge to breast feeding. The symphysiofundal height and the heart beats of the baby are checked depending on the age of the pregnancy.

Also, your healthcare provider will look out for signs and symptoms of domestic violence or even ask if you are a victim. The information is sought in confidence and if you are not comfortable to talk about it in that visit you can do so when you feel comfortable in the next visit. This is important so that the aim of antenatal care is not defeated. Victims of domestic violence might not be able to comply with their antenatal visits as their partners might not support them. Also, giving a history of domestic violence will help your healthcare provider to link you to the appropriate authority to handle the case. Most hospitals have social services and legal units which your healthcare provider might refer you to and there may be the need to report the case to the police. In some countries there are support groups for victims and even shelters for those who will not be safe in the immediate period going back to their homes after reporting the abuse.

Furthermore, your healthcare provider will seek information on female genital mutilation also known as female circumcision or female genital cutting. Female genital mutilation is a form of domestic violence against the girl child. In some countries, personal information of victims of female circumcision at booking clinic are collected and submitted to their database. This information is sought from you and discussed to show you that it’s wrong to sustain such cultural practices. In some countries, the healthcare provider will report the victim to the police or social services if the unborn female child is at risk of female genital cutting. There are different degrees of female genital mutilation and for some, surgery has to be done to open up the vagina. Apart from the problem with sexual satisfaction and painful sex associated with female circumcision, there is the obstetric problem of difficulty during delivery, perineal tear, heavy bleeding after delivery, prolonged labour and even still birth.

Advise on lifestyle modification (smoking, alcohol consumption), diet, exercise, changes in pregnancy are given during the antenatal care visit. This is not different from those given at the preconception counselling and care clinic for those who had such clinic visit before pregnancy. These advice are given through special antenatal classes or at the clinic by the healthcare provider before consultation begins. This can be in person or through playing of a video recording. Tetanus toxoid vaccine is given at booking as well as routine antenatal medications.

WHO PROVIDES ANTENATAL CARE

This care is provided by the midwives, general practitioners and obstetricians. It also depends on the level of healthcare whether primary, secondary or tertiary. Women often prefer to be seen by one particular healthcare provider which is good but it is not feasible most of the time. Women are often seen by a group of doctors in a unit and every information is clearly written in their records. This makes it easier for any other doctor to continue care from where the last doctor stopped. In some settings, the woman can access her antenatal record electronically or the records are handed to her, this is important for easy update of healthcare providers at another facility if she decides to transfer her care to another or there is an emergency and she needs to seek care remote from her primary place of antenatal care. In some facilities, such records are not available due to lack of technology or for fear that the woman might misplace her antenatal records, such facilities keep the records and only make them available in written form to the woman on demand.

THE FREQUENCY OF ANTENATAL CARE VISITS

The frequency of antenatal care visits is often dependent on the risk category of the pregnancy whether low or high risk. Traditionally, women are seen 4 weekly until 28weeks of pregnancy, 2 weekly until 36 weeks and weekly until delivery. According to the world health organization focused antenatal care model, only four visits are needed; first visit from 8 to 12weeks, second visit from 24 to 26weeks, third visit at 32weeks and fourth visit from 36 to 38weeks. At 41weeks if delivery has not occurred induction of labour might be carried out by sweeping the membrane at the clinic.

ANTENATAL SCREENING TEST

Some screening tests will be requested at the booking clinic while some are requested at specific periods during the course of the pregnancy. Such screening tests are requested after proper counselling on the purpose they serve and the interventions available when the results are out. They include screening for anemia, blood group and red cell antibodies, genotype, infections such as HIV, syphilis, hepatitis and urinary tract infection. Ultrasound scan is also used to screen for structural abnormalities and monitor growth of the baby.

Apart from the use of scan in early pregnancy to know the location of the pregnancy, it is also used to know the number of babies and whether they share the same sac or placenta. The age of the pregnancy and expected date of delivery can also be estimated from the scan. In some countries, screening for chromosomal abnormalities such as down’s syndrome can be suspected from an early scan in women at risk of having babies with the syndrome. Women at risk of diabetes and hypertensive diseases in pregnancy are also screened. At each visit the blood pressure and urine are checked for signs of possible development of pre-eclampsia a form of severe hypertensive disease in pregnancy.

The symphysio-fundal height is also checked at each visit to assess the growth of the baby. The screening tests are very important as they are used to identify complications in pregnancy, us to

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