By Abu Bakar Abdul Majeed
The Sun, September 26, 1995
PHYSIOLOGICALLY, THERE ARE THREE species of homo sapiens - the male, the female and the pregnant. The pregnant is different from its less conspicuous counterparts in a number of ways.
Total blood volume in pregnancy increases by 30-40% (1.5-1.8 litres). The protein component of blood plasma is also lower in pregnancy, whilst kidney function is improved. The heart and blood vessels also undergo changes. The output from the heart increases by about 30% due to a higher heart rate. However, the blood pressure normally remains relatively constant during normal pregnancies. Food moves slower in the digestive tract of a pregnant woman and this often leads to constipation.
Since the effects of drugs are dependent on the physiology of the body, examples of aberrations cited above would definitely create a problem in the treatment of pregnant patients. However, a woman should not endanger her health by giving up needed drugs. This article discusses the safety of drug usage in pregnancy.
Nausea and vomiting is relatively common in pregnancy. They are normally mild and referred to as "morning sickness". This problem usually starts in early pregnancy and lasts for 12 to 14 weeks. Severe nausea and vomiting that persist may be detrimental to the patient and the foetus. It may lead to nutritional deficiencies, weight loss and starvation. The patient may require hospitalisation with administration of replacement therapy and electrolytes, anti-emetics and sedation.
The mechanisms of nausea and vomiting in pregnancy is still unclear. Therefore, treatment is directed toward the symptoms. Normally dietary management should be sufficient. This should include small, dry meals high in carbohydrates. Spicy food and noxious odours should be avoided. If nausea persists, the patient may have to take medication.
Although teratogenic risk cannot be ruled out for any drug, the risk involved in using nausea and vomiting-prevention drugs seems to be small. The two drugs with the lowest risk for teratogenicity appears to be meclizine and dimenhydrinate. Nevertheless, these drugs should only be used with extreme care and after consultation with the doctor.
Heartburn usually occurs during the latter half of the pregnancy. This results from food being pushed upwards from the stomach by the enlarging womb. Dietary management, in the form of small meals can help to alleviate the problem.
Pregnant women may also benefit if the head of the bed is elevated slightly. Drugs known as antacids such as aluminium and/or magnesium hydroxide may be used, with caution, in patients who do not respond to dietary management.
Constipation is another common problem in pregnancy and is most likely a result of decreased movement of the digestive tract, including the bowel. Dietary advice would include the taking of bulky, high fibre foods and increasing fluid intake. Moderate exercise may also help. However, if the problem persists, then the use of emollient and bulk laxatives are the agents of choice in the pregnant patient.
Haemorrhoids often develop or worsen in pregnant patients. This may be due to the increased pressure of the womb, and this is often made worse by constipation. Many patients improve after cessation of constipation or regular use of stool softeners. However, if drugs are to be used, external products are preferred because many drugs are readily absorbed from the rectum. Anal painkillers containing surface anaesthetics should be avoided because of possible absorption into the blood. And these may finally end up in the foetus.
The take-home message is simply this. If you have physiological disturbances related to pregnancy and are thinking of resorting to medication to alleviate the problem, make sure that you consult your doctor or pharmacist. This is to protect both the mother and foetus.
Besides drugs, mothers who suffer from chronic diseases may pass some of the undesirable effects onto the foetus. An example is the metabolic disorder diabetes mellitus or high blood sugar. In this disorder, glucose is not efficiently utilised as a source of energy for the body and therefore accumulates in the blood. In early pregnancy, this high blood sugar produces defects in the development of the embryo's rear part of the backbone and leg. In late pregnancy, it results in oversized babies and foetal acidosis which can be fatal to the unborn.
Then there is a metabolic disorder known as phenylketonuria, which is due to the accumulation of an amino acid, phenylalanine. Amino acids are normally used by the body to build up the required proteins. However, in phenylketonuria, the excess acid may poison the central nervous system and lead to mental retardation if untreated.
A foetus in the womb of a mother with phenylketonuria may be at risk of nervous-system injury prior to birth even though it does not have the disease. Mothers at this risk can readily be identified by measurement of their blood phenylalanine level. If you are concerned, talk to your doctor or pharmacist.
High blood pressure or hypertension affects the foetus as well. Hypertensive patients have a greater incidence of decreased foetal weight and foetal growth retardation due to decreased function of the placenta.
Pregnant patients with epilepsy, regardless of whether they are on medication or otherwise, may have a higher risk of delivering an infant with congenital abnormalities and mental retardation.
The effects of mild asthma on pregnancy is generally not a problem. However, severe asthma with breathing difficulties or other medical problems may have an effect on the outcome of the pregnancy. In cases like these, a planned pregnancy is very much advocated.
Living in an urban environment, being constantly exposed to car exhaust, cigarette smoke, radiation from video display terminals and the host of additives in foods may also result in foetal defects.
The five articles in this series have briefly touched on the various aspects of how to keep the unborn under good protection. This is important because to indulge in anything that may jeopardise the safety of the foetus would be tantamount to a form of child abuse.
The writer is an associate researcher at the National Poison Centre and lecturer at the School of Pharmaceutical Sciences, Universiti Sains Malaysia.
