TOP 10 SUBSTANCES TO AVOID DURING PREGNANCY

Pregnancy is a period during which a woman carries a fetus in her womb until the time of birth. Medically, pregnancy is dated from the outset of the last normal menstrual period. From this time till parturition, pregnancy lasts approximately nine months. This period of pregnancy is called the gestational period. A significant time in this period is the first eight weeks of the fetus’ life called the embryonic period. During this period, the embryo is more vulnerable to the risk of teratogens (substances that can cause abnormal growth of a fetus).
Thus, for the period a fetus spends in the womb, there is a constant struggle for existence by that fetus. It is therefore mandated that every pregnant mother provides and maintains a conducive environment for the development of the fetus. This can be done by avoiding some specific substances which when taken, is a risk factor for birth defects (abnormal developmental structure of the fetus) or worse still, spontaneous abortion (premature expulsion of the fetus).
Below is a list of top ten substances which every pregnant mother should avoid for the proper growth and development of her baby.
1. ALCOHOL
Alcohol, whether high or low is bad for the health of an unborn baby hence should be completely avoided during pregnancy. Alcohol alters normal developmental mechanisms (such as cell division, cell induction and cell differentiation) and thus is a high risk factor for the occurrence of birth defects.

Babies who were born to pregnant women who have taken alcohol have been shown to exhibit a particular pattern of birth defects called the fetal alcohol syndrome.
Babies with this syndrome have  mental deficiency, microcephaly (small head), eye anomalies and joint problems.
2. CIGARETTE
Cigarette smoking is another cause of birth defects in babies. Statistics show that premature delivery is twice as frequent in mothers who smoke than the ones who do not smoke. Maternal smoking during pregnancy is linked to the cause of intrauterine growth restriction (restricted growth of the fetus while in the womb). The mechanism for this is that nicotine, the active ingredient of cigarette, is a vasoconstrictor and constricts the uterine blood vessels, decreasing blood flow to the uterus hence leading to poor nutrient supply to the developing baby. Hence, cellular growth and development is altered leading to a range of birth defects.
3. ANTIBIOTICS
Antibiotics are drugs used in the treatment of a myriad of bacterial infections. As bacterial infections are among the most commonly encountered infections, antibiotics are among the most commonly used drugs in everyday life. Examples of antibiotics include streptomycin, dihydrostreptomycin and tetracycline. Though these drugs are not harmful to non-pregnant women, they are very harmful to the developing baby and hence should be avoided by pregnant women.
Research has shown that intake of high doses of streptomycin during pregnancy has been linked to deafness in newborns. Another antibiotic, tetracycline, has been shown to cause tooth defects even when taken in relatively low to moderate quantities.

4. VITAMIN A
Though a very essential nutrient during pregnancy, high intake of vitamin A during pregnancy has been reported as a high risk factor for birth defects. It is usually advisable for pregnant women to abstain from vitamin A (or take in low quantities) during the embryonic period (third or eight weeks of the developing baby’s life). During this period, the risk of spontaneous abortions and craniofacial defects with high intake of vitamin A is very high.
5. HARD DRUGS
Hard drugs (or illicit drugs), such as marijuana, cocaine and heroine are strong human teratogens.
Cocaine, the most used hard drug in pregnant women, has been reported to cause placental anomalies.
Most hard drugs generally affect the behavior of the baby and are called behavioural teratogens. They mainly alter CNS (brain and spinal cord) functions.
6. ORAL CONTRACEPTIVES
Oral contraceptives are pills which are taken by women to prevent conception (fertilization of an egg by a sperm). Though it is illogical for a pregnant woman to use contraceptive, some women who were previously taking oral contraceptives still take it during their early stages of pregnancy while being unaware that they are pregnant.
The intake of oral contraceptive during pregnancy causes hormonal imbalance. Contraceptive pills alter implantation by blocking the production of progesterone by the corpus luteum. Progesterone increases the vasculature and thickness of the uterine wall hence aiding implantation of the blastocyst. Thus, impairment of progesterone balance during pregnancy can lead to spontaneous abortions. It is therefore important that any pregnant woman of childbearing age avoid the use of oral contraceptives.
7. THALIDOMIDE.
Thalidomide is an immunomodulatory drug used mainly for the treatment of leprosy, nausea and multiple myeloma. It is a very potent teratogen. Pregnant women can get exposure to this drug while undergoing cancer treatment or while trying to control nausea.
The main effect of thalidomide exposure during pregnancy is a range of limb defects in the fetus. These defects include meromelia (absence of part of a limb), Amelia (absence of limbs) and micromelia (abnormally small or short limbs). Other  teratogenic effects of thalidomide are heart defect, defective intestine and defective urinary system.
8. RADIATION
High levels of radiation exposure during pregnancy can cause damage to the developing fetus. The degree of the damage is proportional to the amount of radiation absorbed.
Exposure to radiations can be via: medical x-ray (x-ray diagnosis or therapy), television and computer screen, airplane trips, telephone and industrial workplace.
Exposure to radiations such as x-rays cause damage to the central nervous system (brain and spinal cord). Thus, the baby has problems with learning, memory, communication and general perception of the environment.
9. MERCURY
Mercury is a shiny pinkish metal in liquid form. It is the only metal in liquid form. Exposure to mercury even in small quantities can cause serious developmental effects to the fetus. Even to adults, mercury is a very dangerous poison, not the least of the unborn child. Exposure to mercury can be from eating fish containing mercury (such as shark and king mackerel), dental fillings and damaged fluorescent light bulbs.
Mercury alters the developmental mechanisms of the fetus. It alters the division of cells and their differentiation into specialized tissues. It leads to unpredictable mutations which have a harmful effect on the fetus. It also causes mental deficiency and muscular abnormalities.
10. CONTAMINATED FOOD
It is very important that a pregnant mother watches what she eats and even touches because the fetus is especially vulnerable to infections agents. A popular parasite, toxoplasma gondii, which causes toxoplasmosis, has a very potent teratogenic effect to a fetus. This parasite can be found in contaminated animals, soil and vegetable. Since it is often difficult to determine a contaminated food by merely looking at it, it is compulsory for pregnant mothers to eat only thoroughly cooked food.
The main effect of infections such as toxoplasmosis is mental deficiency. Often, the fetus may develop small head, (microcephalus) and big head (hydrocephalus).
In addition to eating thoroughly cooked meat, it is advisable that pregnant mothers also avoid contact with animals and drinking unpasteurized milk.