If there's one big change that almost every woman reports during pregnancy, it's thicker longer hair and awesome hair days. Thank those extra hormones, because it's their job to make sure that baby in your body grows strong and healthy. A side effect is that the extra hormones shift your hair's growth cycle, keeping your hair in the growth phase during your entire pregnancy. Basically, all that hair that you normally shed on a daily basis, stops falling out. You'll find that you may not shed a single hair while your pregnant.
Some research suggests that hair strands actually get thicker while a woman is pregnant. Meaning the diameter of each hair increases during pregnancy.
Unusual hair loss while you are pregnant happens to very few women. If you experience hair loss, this may be due to a vitamin or mineral deficiency, and mentioning it to your physician is highly recommended.