Pregnant students in undergraduate chemistry labs --
As regards air quality as well as all other laboratory hygiene and protective safety measures, the teaching labs are as good or better than any workplace -- i.e. they are as good as or better than OSHA requires for employees' work environments even though students in teaching labs are not employees and OSHA regulations do not apply to student safety.
However, for most chemicals, very little is known about how a developing fetus will be affected by exposure of its mother to small quantities of the chemical -- air exposure, skin exposure, ingestion (for example a person touching his/her lips after having touched a surface that contained invisible traces of chemical).
Medical doctors often write recommendations or statements for pregnant students, to the effect that the student may take part in the laboratory exercises "if work with volatile and toxic substances is performed in a fume hood, and standard safety and personal protective equipment are used, so that the student not at risk for coming into contact with possibly injurious substances." This is bogus; this is a CYA phrase. The lab is full of students wielding numerous possibly injurious substances, and there is no way that the University can guaranteed that the student is not at risk.
Pregnant lab students who do not wish to risk any possibility of exposure to chemicals in the lab are encouraged to consider withdrawing or taking an incomplete, because the only way to come anywhere close to avoiding that risk is to not be in the lab.
On the other hand, many students recognize that there is no such risk-free environment anywhere, and that the world as a whole, e.g. food additives, hair dye, air pollution.... offers many risks for contact with possibly harmful substances whose effects on the fetus are not known. Pregnant students are encouraged to continue in the lab, focusing on excellent lab hygiene and safety practices, if they are are comfortable with the idea that the risk is minimal and acceptable and that standard PPE and safety practices, properly employed, will afford adequate protection.