OB-GYN 101

• Thermal Stress
• Noise
• Vibration
• Chemicals
• Cathode Ray Tubes

Thermal Stress
Fetal enzyme systems may not function properly if subjected to unusually high temperatures. In laboratory animals, elevation of core temperature is associated with an increased risk of fetal loss. For this reason, pregnant women are generally restricted from saunas and Jacuzzis. It is difficult, however, to elevate one's core temperature by sitting in a sauna or Jacuzzi, often requiring a very long exposure at very high temperatures.

The important thing to avoid is elevation of the core temperature. Any activity which may lead to an elevation of core temperature should be restricted. This would include sedentary exposure to high ambient temperatures which would otherwise be tolerated by a non-pregnant person, or moderate exercise in moderately-elevated temperatures.

Pregnant women are at a disadvantage in hot environments for several reasons:

1. They have a high metabolic rate because of the fetus and placenta, generating extra heat.

2. Their surface area to mass ratio is unfavorable. They have increased their mass without a proportionate increase in surface area, making it more difficult to dissipate heat.

3. When they vasodilate to shunt blood to their skin for cooling, the rest of their cardiovascular system is a little sluggish in compensating, leading to easy fainting.

Noise
The abdominal wall muffles (attenuates) the noise only somewhat and these very noisy areas may pose significant problems for the developing fetus, including hearing loss.

While it is possible to provide the mother hearing protection against loud and possibly damaging noises, it is not possible to protect the fetus. There is an approximately 15 dB attenuation (quieting) of sound as it passes through the mother's abdomen and is heard by the fetus. This means that a woman exposed to continuous 115 dB of loud rock music can protect her own hearing by wearing hearing protection, but the fetus will still be exposed to continuous 100 dB sound, enough to cause damage. Continuous exposure to 85 dB and above is considered dangerous to the mother's hearing.

Pregnant women should wear hearing protection when exposed to ambient noise levels above 84dBA, including infrequent impact noise. (So should non-pregnant women and men.)

Brief exposure (5 minutes per hour or less) of hearing-protected pregnant women to ambient noise above 84dBA in order to transit high noise areas is probably safe. Prolonged exposure to this level of noise is not recommended.

Pregnant women should avoid any exposure to ambient noise greater than 104dBA (corresponding to the need for double hearing protection), unless absolutely essential for quickly moving through a high noise area.

Vibration
Low frequency, whole body vibration can be problematic for a developing pregnancy.

This is the type of shaking vibration one might experience if operating a jackhammer or driving at high speed over a highway with many potholes. It is to be avoided during pregnancy.

Chemicals
Organic solvents, such as turpentine, fuel, oils, lubricants, and paint thinner may have adverse effects on a developing fetus.

The greatest risk comes from ingestion of these solvents, or by chemical spills with contamination of the skin. Inhalation, though less likely to delivery significant quantities of the material, should also be avoided.

It is very important to avoid maternal exposure to lead, cadmium and mercury.

Cathode Ray Tubes
There is no good evidence that working in front of a CRT (Cathode Ray Tube) poses any threat for the pregnant woman, either from electromagnetic radiation (EMR) or from eyestrain.

Ergonomics are important for all sitting personnel, and particularly pregnant women. Good low back support, correct height for the CRT, wrist support and proper positioning of the legs (with the thighs flexed slightly so the knees are at least level with the hips, if not slightly higher than the hips), will contribute to the comfort and performance of these personnel.