Human development from conception to birth is a highly critical period of child growth. This period determines the later life of the child; either the child will survive or thrive. Research shows that everyday many babies are born prematurely with birth defects and with low birth weight (LBW) across the world. These are the leading causes of death in newborns. Environmental hazards such as smoking, drugs and other toxins also cause physical defects in the developing embryo or fetus and can result in birth defects. Some toxins in the environment can cause birth defects in newborns as well. While exposure to many chemicals will not lead to abortion and birth defects, some chemicals or other toxins can lead to serious consequences such as  abortion, fatal birth defects, fetal growth, retardation, prenatal death, low birth weight and developmental delays in infant. 

Inhalation, ingestion, or skin absorption are the three ways by which a pregnant woman can be exposed to teratogenic chemicals. Depending on the stage of pregnancy at which contamination occurs, the effects of exposure can be very serious, for both the mother and the baby. In developed countries, smoking is the leading cause of LBW, followed by low maternal weight gain during pregnancy.

In Pakistan, the prevalence of smoking in women is reported to be low (3.5%) (Nasir and Rehan 2001); use of inhaled (huqqa) and chewing tobacco, however, is not uncommon in rural areas (Khan and Siddiqui 2002). Also up to 70% of households in the country use wood, biomass, and/or crop residues as cooking fuel, whereas 53% of households use wood alone as cooking fuel. Maternal exposure to wood fuel smoke may lead to impaired fetal growth from smoke constituents such as carbon monoxide and particulate matter.  (Rehfuess et al. 2006; WHO 2005)

Pregnant women need to avoid potentially harmful substances and conditions both at home and at work. Some of the common potential hazards that pregnant mothers need to avoid during pregnancy are described here.

Lead
Exposure to high levels of lead during pregnancy can cause miscarriage, pre-term delivery, low birth weight and/ or developmental delays in the infant. Lead toxicity in children is characterized by behavioral and learning problems and anemia.

Women who live in old homes may be exposed to higher levels of lead due to deteriorating lead-based paint. A pregnant woman is exposed to significant amounts of lead in her drinking water if her home has lead pipes, lead solder on copper pipes or brass faucets. It is recommended that running water for 30 seconds before using it for drinking or cooking helps reduce lead levels. A pregnant woman should use water from the cold water pipe for cooking, drinking and later for preparing baby formula since it contains less lead than hot water. Many home filters do not remove lead, so a pregnant woman should read the label on her filter carefully and change the filter as recommended.

Unexpected sources of lead in the home may include the wicks of scented candles (which release lead particles into the air when burned) and the plastic (polyvinyl chloride) grips on some hand tools. Even some arts and crafts materials (e.g., oil paints, ceramic glazes and stained glass materials) contain lead. A woman should try to stick with lead-free alternatives (such as acrylic or watercolor paints) during pregnancy and breastfeeding.

If anyone is exposed to lead on the job (such as painters and those working in smelters, auto repair shops, battery manufacturing plants or certain types of construction), they should change their clothing and shower at work to avoid bringing lead into the home. They should wash contaminated clothing at work, if possible, or wash it at home separately from the rest of the family’s clothing.

Mercury
Mercury is another metal that is present naturally in the environment. Mercury enters the environment from natural and man-made sources (such as coal-burning or other industrial pollution). It is converted by bacteria to a more dangerous form (methyl mercury) that accumulates in the fatty tissues of fish. While trace amounts of mercury are present in many types of fish, mercury is most concentrated in large fish that eat other fish. Methyl mercury is found in some fish and seafood and can adversely affect the fetus. It is therefore advisable to limit fresh/frozen tuna fish and lake trout to one meal/month.

It’s less certain whether exposure to elemental mercury, which is used in thermometers, dental fillings and batteries, poses a risk in pregnancy. Some studies have found an increased risk of miscarriage in women working in dental offices. Women who work with mercury should take all recommended precautions to reduce their exposure.

Arsenic
Arsenic and cadmium are two other metals that are suspected of posing pregnancy risks. These metals enter the environment through natural (weathering of rock and forest fires) and man-made (mining and burning of fossil fuels and waste) forces. Women working at or living near metal smelters may be at increased risk of miscarriage and stillbirth.

Research shows that chronic Arsenic Toxicity may have varied presentations from non cancerous to malignancy of skin and different organs, dermal lesions and other skin disease. Ground water of some areas of Sindh and Punjab are highly contaminated by Arsenic (Ahsan T. 2009; Kazi TG.  2009). A study conducted in Bangladesh found that drinking tube well water with more than 50 microg arsenic per liter during pregnancy increased the risk of fetal loss and infant death.(Rehman A 2007). Women of reproductive age should be prioritized for mitigation where drinking water is contaminated by arsenic.

Pesticides
Pregnant women should avoid pesticides, whenever possible. There is no proof that exposure to pest-control products at levels commonly used at home pose a risk to the fetus. However, all insecticides are to some extent poisonous and some studies have suggested that high levels of exposure to pesticides may contribute to miscarriage, preterm delivery and birth defects.

Organic solvents
Organic solvents are chemicals that dissolve other substances. Common organic solvents include alcohols, degreasers, paint thinners and varnish removers. Lacquers, silk-screening inks and paints also contain these chemicals.

Pregnant women, who work with solvents, including women who do arts and crafts at home, should minimize their exposure by making sure their workplace is well ventilated and by wearing appropriate protective equipment, including gloves and a face mask. They should never eat or drink in their work area.

Household cleaning products
While some household cleansers contain solvents, there are many safe alternatives. Pregnant women should read labels carefully and avoid products (such as some oven cleaners) whose labels indicate they’re toxic. Products that contain ammonia or chlorine are unlikely to harm an unborn baby, though their odors may trigger nausea in an expectant mother. A pregnant woman should open windows and doors wear rubber gloves when using these products. She should never mix ammonia and chlorine products because the combination produces fumes that are especially dangerous for the child.

A pregnant woman who is worried about commercial cleansers can use alternatives. For example baking soda can be used as a powdered cleanser to scrub greasy areas, pots and pans, sinks, tubs and ovens. A solution of vinegar and water can effectively clean many surfaces such as countertops.