Antenatal check-up

Fetal abnormalities can be detected through antenatal checks during antenatal visits. Depending on mother's family history, medical background, previous pregnancies and age, your doctor may recommend a range of tests deemed suitable.

Routine tests :

At your initial visit, your caregiver will take a blood sample and feel your abdomen; at this and subsequent visits your blood pressure (BP) and urine will be assessed. Most often, hospitals and clinics schedule appointments every 4 weeks until week 28, then it becomes every 2 weeks until week 36 and then weekly.

Blood and Urine tests

Blood test is taken to check blood group, hemoglobin levels (to check for anemia) and immunity to rubella (a postnatal vaccination will be given if you are not immune). This blood test also checks for Aids, syphilis, diabetes, hepatitis and rhesus status. The blood pressure reading taken at your first visit will be used as a barometer to measure subsequent readings. It is normal for your BP to be higher in the later part of pregnancy. Urine is checked for ketones, protein and glucose.

The presence of

• ketones affects the transportation of oxygen in the blood
• protein indicates preeclampsia or some infectionUltrasound scanning The scan is pain-free and there is no risk of miscarriage. It is routinely done at 16-18 weeks. High pitched sound waves are reflected back off the baby and replicated electronically as an image on a screen. It confirms dates and multiple pregnancies, detects abnormalities and placental position.

Special tests

Most of these tests are optional; you are not obliged to have them. Your decision should be based on sound judgment; you must understand what is being offered and why, and also the risks involved. Finally you should consider the possibility of the results being positive and whether or not to terminate the pregnancy. Support and counseling services are available in case of such an outcome.

Transvaginal scan

Carried out from 5-6 weeks, a probe is inserted into the vagina giving a clear view of the developing baby.

Advantages - results are instant

Disadvantages - baby is exposed to high frequency sound

CVS (chrorionic villus sampling)

Detects chromosomal and genetic disorders such as Downs's syndrome and sickle cell anemia. A tube is inserted into the uterus at 8-12 weeks and cells are taken from placental tissue surrounding the embryo.

Advantages - very accurate and preliminary results within 48 hours

Disadvantages - risk of miscarriage (roughly 1 in 100)

Nuchal test

Non-invasive ultrasound scan carried out at 12 weeks to detect chromosomal disorders. 'Nuchal' means neck: the scan checks for abnormal thickness in the fold at the back of the baby's neck. When combined with a blood test, this test is 80-90% accurate in predicting Down's syndrome.

Advantages - non invasive and no risk of miscarriage

Disadvantages - none

AFP (alpha-fetoprotein test)

Blood test that checks blood protein levels and neurological problems such as spina bifida or hydrocephalus. It is carried out at weeks 15-18. Accuracy is not good: high and low levels of alpha-fetoprotein can be found in women carrying healthy fetuses and those who are very nauseous. Results take about 10 days.

Advantages - non invasive with no side effects

Disadvantages - 50% accuracy, false positive rate of 5-10%

Amniocentesis

Sample of amniotic fluid taken under local anesthesia through the abdominal wall at 16-18 weeks to test for disorders such as Down's syndrome. Results in 2-3 weeks

Advantages - accuracy of 90%; reveals baby's gender which is important with some disorders

Disadvantages - risk of miscarriage (less than 1 in 100); discomfort, side effects such as bleeding, infection; screens few defects

Triple/Quadruple/Leeds/Bart's tests

Combination of blood tests to assess risk of chromosomal defects or problems such as anencephaly (absence of a brain) or spina bifida.

Advantages - no risk of miscarriage

Disadvantages - accuracy between 60 - 80%