It is not some common reaction during pregnancy but possible. Some women experienced these uncommon side effects of pregnancy. Their hair gets thin and weak and their eyelashes and even eyebrows fall out. Normally hair (including the eyelashes and eye brows) won’t get thinner because the increased estrogen hormones would stimulate the growth of hair. Usually women might experience hair loss after the delivery for the decreasing level of estrogen hormones. But if you experience extremely apparent hair loss or your eyelashes and eye brows fallen out, it probably is sending some signals. As to hair loss during pregnancy, it might be related to a vitamin or mineral deficiency. Vitamin B, C, E and biotin are important to keep hair thick and strong. If your eyelashes and eyebrows are getting thinner and shorter, it is probably caused by nutrition deficiency or thyroid dysfunction. Thyroid changes during pregnancy due to the changes of estrogen, but it will ends with the ending of pregnancy. You can have a test of your protein level and thyroid. Meanwhile you can apply some vitamin productions to help eyelashes growth.