n. the removal of a sample of fetal blood by inserting a fine hollow needle through the abdominal wall of a pregnant woman, under ultrasound guidance, into the umbilical vein. Cordocentesis is most commonly performed for confirmation of fetal *packed cell volume prior to intrauterine transfusion in cases of haemolytic disease of the newborn or for confirmation of infection in the fetus. See also fetal blood sampling.
Inspection of a FETUS by passing a ?breoptic instrument called a fetoscope through the abdominal wall of a pregnant woman into her UTERUS. The procedure is usually conducted in the 18th to 20th week of pregnancy to assess the fetus for abnormalities and to take blood samples to preclude diseases such as HAEMOPHILIA, DUCHENNE MUSCULAR DYSTROPHY and sickle-cell ANAEMIA. The procedure should be used only if there is a serious possibility of abnormality, the presence of which will usually have been indicated by other screening tests such as ULTRASOUND and tests of blood obtained by (intrauterine) cordocentesis (withdrawal of blood by syringe inserted into the umbilical cord).... fetoscopy
The branch of medicine dealing with pregnancy and giving birth. Derived from the Latin word for midwifery (see MIDWIFE), it is closely allied to GYNAECOLOGY. It is concerned with the health of the woman and fetus, from early in pregnancy through to a successful labour and delivery. Pregnancy and childbirth are, however, normal physiological events and for most women they take place without complications. Nevertheless, if something does go wrong, skilled medical care should be immediately available to help the mother and baby achieve a successful outcome. Routine monitoring of pregnancies by midwives and, where necessary, general practitioners or obstetricians is well recognised as a signi?cant contribution to a successful pregnancy and delivery. Such monitoring has been greatly facilitated by advances in ULTRASOUND, AMNIOSCOPY, and amnioand cordocentesis (see PRENATAL SCREENING OR DIAGNOSIS). Numerous problems may occur at all stages, and early detection, followed rapidly by sensitive and appropriate treatment, is vital. Doctors and nurses can specialise in obstetrics after suitable training. (See also PREGNANCY AND LABOUR.)... obstetrics
Prenatal screening of fetal abnormalities may be the result of screening tests carried out on most or all pregnant women, or as the result of speci?c diagnostic tests performed to detect speci?c conditions. Prenatal diagnosis is important as it will identify babies who might need medical or surgical treatment before or soon after birth. In addition, it may also detect severe abnormalities for which parents might decide to have a therapeutic ABORTION.
ULTRASOUND scanning is probably the most widely used diagnostic tool in obstetric practice. It can detect structural abnormalities such as SPINA BIFIDA and CLEFT PALATE and even cardiac and renal problems. A series of scans can assess whether the baby is growing at a normal rate; ultrasound may also be used to assist with other diagnostic tests (e.g. AMNIOCENTESIS – see below).
Tests on the mother’s blood can also diagnose fetal abnormalities. Alphafetoprotein (AFP) is produced by babies and ‘leaks’ into the AMNIOTIC FLUID and is absorbed by the mother. In spina bi?da and other neural-tube defects there is increased leakage of AFP, and a blood test at 16 weeks’ gestation can detect a raised level which suggests the presence of these abnormalities.
The triple test, also performed at 16 weeks, measures AFP and two hormones – HUMAN CHORIONIC GONADOTROPHIN and unconjugated OESTRADIOL – and is used in diagnosing DOWN’S (DOWN) SYNDROME.
Amniocentesis involves inserting a needle through the mother’s abdominal wall into the uterus to remove a sample of amniotic ?uid at 16–18 weeks. Examination of the ?uid and the cells it contains is used in the diagnosis of Down’s syndrome and other inherited disorders. The test carries a small risk of miscarriage.
Chorionic villus sampling may be used to diagnose various inherited conditions. A small amount of tissue from the developing PLACENTA is removed for analysis: this test has the advantages of having a lower incidence of miscarriage than amniocentesis and is carried out at an earlier stage (9–13 weeks).
Analysis of a blood sample removed from the umbilical cord (cordocentesis) may diagnose infections in the uterus, blood disorders or inherited conditions.
Direct observation of the fetus via a viewing instrument called a fetoscope is also used diagnostically and will detect structural abnormalities.
Most tests have a recognised incidence of false positive and negative results and are therefore usually cross-checked with another test. Counselling of the parents about prenatal tests is important. This allows them to make an informed choice which may not necessarily involve terminating the pregnancy if an abnormality is found. (See PREGNANCY AND LABOUR.)... prenatal screening or diagnosis
withdrawal of a sample of fetal blood, either from the umbilical vein during the antenatal period (see cordocentesis) or from a vein in the presenting part (usually the fetal scalp) during labour. The latter procedure is used to detect *hypoxia, by measuring the fetal pH and degree of *acidosis. The normal pH of fetal blood is 7.35 (range 7.45–7.25). The lower the pH, the more likely is the fetus to be suffering from hypoxia and acidosis, indicating an urgent need to deliver the baby.... fetal blood sampling
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