The baby is completely formed by the end of the 12th week of pregnancy and it is usually during these first 12 weeks that the baby can be severely damaged. After about the 16th week when the afterbirth, or placenta, is fully developed and completely functioning it is extremely difficult to harm the foetus because it is then purely growing and maturing.
All drugs should be avoided if possible during the first 12 weeks of pregnancy and certainly no drugs should be taken without the doctor’s advice. Simple drugs such as aspirin for headache, alkali for indigestion, and also mild purgatives if necessary, will cause no harm.
Diseases which may Affect the Foetus
There are many conditions which occur both before and during pregnancy which may adversely affect the health of the foetus. These may be divided into two sections: infections which occur in the mother and are transmitted across the placenta to the foetus (direct infection of the foetus from the vagina while still within the uterus is virtually unknown); general or located diseases of the mother, which, for some reason or another, will adversely affect the baby.
The main infections which may seriously affect the foetus are rubella and syphilis. It affects the baby mainly during the first 12 weeks of pregnancy. The infection is transmitted from the mother across the placenta to the foetus and may damage the eyes, the ears, the heart or other organs as they arc developing. Maternal infection by rubella after the 12th week of pregnancy may not cause congenital abnormality for by this time all the organs are fully developed but the virus may interfere with maturation and cause a hearing defect.
There is evidence that all virus infections may adversely affect the developing foetus and although the incidence of congenital abnormality as a result of rubella is far greater than from other virus infections such as Asian ’flu and mumps, these are nevertheless associated with an increased incidence of congenital abnormality.
Syphilis is caused by an organism called treponema pallidum ‘which can only cross the placental barrier after the 20th week of pregnancy. It may severely affect the foetus and lead to its death within the uterus, or, if the baby lives, he will most certainly be delivered with congenital syphilis. The diagnosis of syphilis at the beginning of pregnancy is of the utmost importance because if it is satisfactorily treated before the 20th week the baby will not be affected.
Toxoplasmosis is an extremely common parasitic disease in the human affecting approximately 30 per cent of people by the age of 3o. Although this is a relatively common disease, very little is known about it or its mode of spread. In the very few instances when a woman develops active toxoplasmosis during the first 12 weeks of pregnancy she does run a small risk that her baby might have his eyesight or other organs affected. Toxoplasmosis is rather like rubella in that a previous attack confers life-long immunity and the only time at which a baby can be affected is when an initial and acute attack occurs in the mother within the first 12 weeks of pregnancy. Despite the very common incidence of toxoplasmosis the number of people who develop toxoplasmosis during early pregnancy is very small indeed and the number of instances of congenital toxoplasmosis is also small.
There are a number of unusual diseases which may also affect the foetus in the uterus, one of which is severe malaria. Apart from the above mentioned diseases, other infections of the foetus within the uterus are extremely rare.
General Diseases affecting the Mother
It is certainly true to say that the foetus within the uterus behaves as a parasite and extracts from the mother as much as it requires for its own growth and nutrition. Certain conditions in the mother, however, do adversely affect her ability to supply the child with its nutritional requirements, or alternatively will lead to the formation of a small placenta so that the foetus cannot grow as rapidly as it might otherwise.
Severe anaemia and deficiency states in the mother may adversely affect her ability to transfer oxygen and other nutritional substances to the baby which may then be retarded in its growth. There are certain factors which seem to prevent the development of a proper placenta and therefore adversely affect the foetus. These include chronic kidney disease, a persistently raised blood pressure and pre-eclampsia. There are also other, as yet unknown, factors which predispose to the development of a small placenta and which may lead to a baby being delivered prematurely or being dysmature. (A dysmature baby is a baby who is small but otherwise perfecdy normal.)
Diabetes may also adversely affect the baby.
A very high temperature can sometimes cause the onset of premature labour.
Traumatic Injury to the Baby in Utero
It is almost impossible to cause physical injury to a baby within the uterus as a result of a direct blow or accident as he is extremely well cushioned. The uterus itself is carefully protected even in a thin woman not only by the maternal spine and pelvis but also by the anterior abdominal wall. The uterus is soft and flexible and the baby lies within a fluid sac inside it. The amniotic fluid in which the baby floats protects him from being harmed by a direct blow. It would take the most violent and severe of blows with a sharp instrument to damage the baby in the uterus. Many women have fallen down stairs and off stepladders without doing their pregnancies or babies any harm despite quite extensive injuries to themselves.
The Immunity of the Foetus
Virus infections of the new-born baby are uncommon. During his time in the uterus and for 6 weeks after delivery the baby has no active immunity to any disease to which he may be exposed because he cannot manufacture antibodies. The diseases which may affect the foetus are discussed above and it will be noted that, with the exception of the viruses, only a few micro-organisms including those of syphilis and toxoplasmosis are capable of crossing the placental barrier to infect the foetus, so that the foetus does not need to develop antibodies against any of the common bacterial diseases. This deficiency is compensated to a certain extent by the passage of antibodies‘ from the mother across the placenta to the foetus. The new-born infant, therefore, possesses antibodies in his blood of approximately the same strength and to the same diseases as those which are present in the mother’s blood. This is known as a passive immunity and after a time, which varies from 6 to 12 weeks, these antibodies gradually disappear from the baby’s blood, and he then becomes susceptible to all these diseases.
Immunity to two most important diseases is not passed from the mother to her baby. One is tuberculosis, to which the new-born infant is particularly susceptible even if the mother has active disease and therefore a high level of antibodies, and the other is whooping cough. A new-born baby must be protected from all infectious diseases and especially these two.
A certain amount of immunity is supposed to be conferred as a result of breast-feeding. Breast-milk certainly contains antibodies to various diseases but it is uncertain how much immunity they confer on the baby.