Work exposure and reproduction

While our knowledge of how different exposures impact an unborn child is still developing, many workplace hazards have been identified as contributing to reproductive health issues. Managing pregnant workers can be particularly challenging due to the multiple risk factors present in various occupations. Given the potentially severe consequences, we emphasize the principle of “better safe than sorry” when it comes to managing pregnant workers.

Risk assessment

The principles and process of risk assessment were thoroughly covered during the first week of this course. Here, we will simply remind you that effective risk assessments rely on two key components: identifying the hazards and evaluating the exposure levels for those at risk.

Health effects

Health effects related to reproductive health include various conditions where the fetus does not develop normally, such as malformations, miscarriage, prematurity, and infertility. Different aspects of exposure can impact outcomes during all reproductive phases.

Before conception:

• Exposure that leads to decreased fertility in either the mother or the father.

Different kinds of exposure can reduce the fertility in both men and women, resulting in no conception. ^{© Colourbox}

During pregnancy:

• Exposure that results in live babies with structural malformations, functional changes, diseases, and prematurity complications, or stillborn babies with structural malformations, functional changes, and complications from abortion or premature birth.

The developing fetus is most vulnerable to toxic chemicals during the first eight weeks of pregnancy and potentially before the woman knows she is pregnant. ^{© Colourbox}

After birth:

• Exposure through breastfeeding causing disease in the child.

Most working mothers can safely breastfeed their babies. However, certain chemicals, such as heavy metals like lead and mercury, organic solvents, and some radioactive substances, have been detected in breast milk at levels that could be harmful to the baby. ^{© Colourbox}

Chemical hazards

When a pregnant woman is exposed to toxic chemicals, the fetus is usually exposed as well, via the placenta. The developing fetus is most vulnerable to these chemicals during the first eight weeks of pregnancy, often before the woman knows she is pregnant. Due to the limited capacity of the fetal liver to detoxify harmful substances, fetuses are particularly susceptible to the effects of toxic chemicals, which can result in birth defects or even spontaneous abortion.

Some basic consepts and definitions:

Carcinogen:
A carcinogen is any substance/agent or mixture that can cause /uncontrolled cell growth.

Mutagen:
A mutagen is any substance/agent or mixture that can causes genetic mutations by altering the DNA of an organism.

Reprotoxic substances:
Reprotoxic substances are any chemicals that can negatively affect reproductive health, potentially causing infertility, developmental issues, or harm to the unborn child. Effects that are transmissible via lactation to breastfed babies are included in this group.

CMR substances:
Carcinogenic, mutagenic, and reprotoxic substances are often grouped together because a single substance can exhibit all three effects. They are classified similarly and are subject to the same legislation. The abbreviation CMR is commonly used to label this group, particularly in safety data sheets (SDSs).

Teratogen:
A teratogen is any substance or agent that can cause developmental abnormalities or birth defects in a developing embryo or fetus. These agents can interfere with normal development, leading to a range of congenital malformations or functional deficits.

Women are at risk of exposure to CMR substances in various occupations, such as laboratory assistants, healthcare personnel and pharmacists handling chemotherapeutic drugs, and workers in chemical process industries. Pregnant women and women of childbearing age should not handle these substances until a risk assessment has been conducted and appropriate measures have been taken to minimize exposure.

Laboratory assistants potentially handle many different chemicals that are classified as CMR substances. ^{© G. Tjalvin}

Farmers and employees in the floriculture industry are also at high risk, as many pesticides are classified as CMR substances. Additionally, many pesticides are fat-soluble and can accumulate in the body’s fat tissues. ^{© Colourbox}

Exposure to organic solvents is considered harmful for pregnant women at levels well below accepted occupational exposure limits, even though many are not classified as CMR substances. However, some organic solvents are classified as teratogens. Additionally, some heavy metals, such as lead and mercury, are classified as teratogens, and pregnant women should avoid exposure to these.

Workers in the paint industry are exposed to various organic solvents. Some studies have observed an association between maternal exposure as a painter and childhood leukemia in their children. ^{© G. Tjalvin}

Biological hazards

Biological agents, such as various viruses and bacteria, can impair fertility among women and men, and be transmitted from the pregnant woman to the fetus via the placenta, with devastating effects. If the mother has not acquired immunity, several infections during pregnancy, including rubella, chickenpox, hepatitis B, and toxoplasmosis, have been linked to birth defects and miscarriages. Healthcare personnel, laboratory assistants, kindergarten assistants, and teachers are at the greatest risk for such biological hazards.

Rubella

Rubella is generally a mild, self-limiting disease, and many cases are subclinical or asymptomatic, especially among young children. Maternal immunity, either through vaccination or natural infection, protects against intrauterine rubella infection. However, the proportion of rubella-susceptible women of childbearing age varies greatly between countries, particularly in developing regions. The most frequent defect associated with congenital rubella syndrome is hearing loss, followed by intellectual disability, cardiovascular defects, and ocular defects. The risk of congenital defects after maternal infection is primarily limited to the first 16 weeks of pregnancy.

Teachers are at risk of being infected by different viruses that could harm a developing fetus. ^{© G. Tjalvin}

Toxoplasmosis

Humans who come into contact with feces from cats infected with the Toxoplasma parasite may inadvertently ingest contaminated material. Food animals such as pigs, chickens, lambs, and goats can become infected in the same way, leading to meat that contains the infectious form of the parasite. Therefore, workers handling raw meat are at risk of infection. If a woman acquires toxoplasmosis for the first time during pregnancy, the infection can be transmitted to the fetus, resulting in congenital toxoplasmosis. As gestational age increases, the risk of fetal infection rises, but the severity of the disease decreases. Congenital toxoplasmosis can cause fetal death, abortion, and in infants, neurological and cognitive deficits.

Contact with cat feces can lead to toxoplasmosis infection. If a woman contracts toxoplasmosis for the first time during pregnancy, it can have severe effects on the fetus. ^{© G. Tjalvin}

Physical hazards

Ionizing radiation
Ionizing radiation is known to have damaging effects on fertility in both women and men. In the developing embryo or fetus, exposure to ionizing radiation can be teratogenic, carcinogenic, or mutagenic. The effects are directly related to the level of exposure and the stage of fetal development. The fetus is most susceptible to radiation during organogenesis (2-7 weeks after conception) and the early fetal period (8-15 weeks after conception). Higher exposure levels may result in spontaneous abortion, growth restriction, and intellectual disability. The risk of childhood malignancy, especially leukemia, is increased regardless of the dose.

Radiologists and others who work with radioactive materials are at risk of exposure to radiation doses that could be harmful to the unborn child. Care should be taken to keep doses as low as possible and within acceptable limits for all, with special limits applying to pregnant women. Rules for radiation dose limits come into effect once a pregnant employee declares her pregnancy.

Ionizing radiation can harm the fertility of both women and men and adversely affect a developing fetus. In-utero exposure to X-rays can increase the risk of childhood cancer. ^{© G. Tjalvin}

Whole body vibration
Whole body vibration has been linked to miscarriages, growth restrictions, fetal death, and premature deliveries. Pregnant women should avoid high levels of vibration and prolonged exposure, especially at low frequencies, which are most harmful during the first and last trimesters.

Noise
Many pregnant women are exposed to workplace noise. Prolonged exposure to loud noise can increase blood pressure and cause fatigue in the mother. Human hearing is fully developed by 24 weeks of gestation. After this period, excessive noise can lead to hearing loss in newborns. The use of personal protective equipment by the mother does not protect the unborn child from noise hazards.

The need for hearing protection for the pregnant woman indicates a harmful environment for the fetus. ^{© G. Tjalvin}

Extreme heat
Heat stress can be problematic for pregnant women due to their reduced heat tolerance. During pregnancy, blood vessels dilate, causing a drop in blood pressure. After birth, heat exposure can lead to dehydration, potentially impairing breastfeeding.

High workplace temperatures can reduce fertility in men. ^{© G. Tjalvin}

Ergonomic factors
Pregnant women experience significant physiological changes, including increased muscle tension and ligament softening due to hormonal shifts. As pregnancy progresses, jobs involving heavy lifting and prolonged standing, combined with these bodily changes, heighten the risk of developing musculoskeletal disorders.

Many women carry heavy weights during their workday. While knowledge about this potential hazard is limited, it is believed that physically demanding work might increase the risk of preterm labor. ^{© G. Tjalvin}

Workplaces and processes should be ergonomically evaluated to reduce risks for pregnant women. Lifting aids should be used to avoid the need for pregnant workers to lift heavy weights, and workstations should be designed to minimize repetitive movements, static postures, and tasks involving twisting or stretching. Risk assessments must consider the physical changes a pregnant worker undergoes and may require modifications at various stages of pregnancy. Additionally, it’s important to assess the increased risk of work-related injuries due to the changing body during pregnancy.

In many occupations, pregnant women face multiple risk factors. For example, hairdressers are exposed to various chemicals and spend most of their working hours standing. ^{© G. Tjalvin}

Psychosocial factors and stress
Pregnancy can reduce a worker’s capacity and cause stress. Long working hours and heavy workloads are linked to an increased risk of preterm birth and low birth weights. High blood pressure can reduce blood flow to the placenta, potentially leading to preterm labor, low birth weights, and pre-eclampsia, which can cause serious, potentially fatal complications if untreated. Additionally, stress has been shown to increase the risk of post-natal depression.