If you're a woman trying to become pregnant, you might wonder what things can hurt or help your efforts at parenthood. Women's fertility begins falling off after the age of 25, and the rate for miscarriage and birth defects increases after 35. Hormonal or immune problems can also complicate conception and pregnancy. Your fertility can also be affected by your mother's exposure to DES (D-E-S), or diethylstilbestrol (dye-thill-still-best-rawl). This is a synthetic steroid of the fifties and sixties used to prevent miscarriages. This drug can cause problems in the growth, development, and function of various reproductive variables. Growth of endometrial tissue outside the uterus, known as endometriosis (in-doh-me-tree-OH-sis), can block the fallopian tubes that are the passageways for the eggs. Ovulation might also be affected by a vegetarian lifestyle, which can cause irregular ovulation and reduce your chances of becoming pregnant. Improper hormone levels can affect your ability to become pregnant as well. Elevated estrogen levels can be caused by obesity. These act as birth control and can keep you from ovulating. Your physician can balance your hormone levels to allow you to ovulate. If you smoke, you increase the risk of ectopic (ECK-top-ick) pregnancy and miscarriage. You can also reduce your chances of becoming pregnant by in vitro fertilization.