Relaxers and pregnancy can be a bad combination.
A relaxer is a concoction typically composed primarily of sodium hydroxide (lye) or calcium hydroxide (lime) that is applied to coily hair to break the disulfide bonds that hold it in it's curly pattern. Breaking these bonds cause the hair to straighten, and achieve the desired effect.
The problem is, the sodium hydroxide, being a strong base (alkali), causes damage to both the hair and scalp if overdone. Even if applied appropriately, the sodium hydroxide causes micro damage to the scalp which results in the lost of protective skin barrier. This results in increased absorption of potentially toxic chemicals. The very chemicals that are mixed with the main ingredient (either the sodium, calcium ore guanidine hydroxide) to create a tolerable "fragrance" or the consistency, or preserve the product.
Then, subsequently, the toxic shampoo, conditioners that are allowed "bake" into the scalp, the toxic moisturizers, oils and sprays continue being absorbed through the raw and damaged scalp. All the while, a new little fetus is desperately trying to grow healthy while simultaneously being bombarded with antiperspirants, make-up, toxic foods, medications, polluted air, contaminated water, and inadvertently through our clothing (detergents, dry-cleaning products).
Mainstream media will tell you "there has been no scientific proof" that these chemicals are harmful to a developing fetus. But what they don't tell you...is there is no proof, period. No proof that it's safe, no proof that it's unharmful. No one tests anything on pregnant humans, so there is *no proof* of anything...and their will likely never be proof. So where does that leave a health-conscious mom-to-be? Rightfully worried and skeptical.
An extrapolation of common logic demonstrates that application of caustic chemicals to the highly vascular scalp of pregnant women, is not a great idea. We do know that there are plenty of hormone disruptors and carcinogens that contaminate common hair-care products. We need our skin barrier to be intact to help preserve the integrity of our bodily functions (including our uterine functions, the complicated hormone milieu of pregnancy, and our mental health).
I would recommend all of these issues be carefully considered, and the risk/benefit ratio considered when deciding to relax the hair during pregnancy.