The first trimester of pregnancy lasts from fertilization to the 13th week. During this time the embryo will implant, form the fetal part of the placenta and develop all its organs. Your body will pump out hormones and produce more blood cells to support the pregnancy. The dramatic changes taking place in your body commonly cause nausea and fatigue in the first trimester. More serious complications include the risk of ectopic pregnancy or miscarriage.
According to the Mayo Clinic, 50 to 90% of pregnant women suffer with nausea in the first trimester. Although commonly called "morning sickness," it is not confined to any one time of day. The high levels of the hormone progesterone supporting your pregnancy also slow your digestive system, contributing to nausea.
There is no cure for morning sickness and usually treatment does not prove necessary. Eating several small meals, avoiding spicy or greasy foods and getting plenty of fluids can help. For most women, the nausea subsides during the 2nd trimester.
Early pregnancy often proves exhausting. Your body needs extra energy to support the pregnancy: Your uterus begins to grow, your breasts enlarge, and you ratchet up the production of blood cells and blood volume. Nausea and vomiting can deplete your energy reserves, and rising progesterone levels make you feel sluggish.
Ectopic pregnancies (also called tubal pregnancies) occur when a fertilized egg settles somewhere outside of your uterus, usually in your Fallopian tubes. The embryo cannot survive outside the uterus and it cannot be transplanted to the uterus. If the ectopic pregnancy is not ended in time, your Fallopian tube could rupture, threatening your future fertility or even your life.
According to "The Essential Guide to Pregnancy and Birth," ectopic pregnancies are usually discovered in the 6th to 7th week of pregnancy, in time to prevent any complications. Early in an ectopic pregnancy you might notice pain in your abdomen that gets worse when you become active, along with vaginal spotting or bleeding. See a doctor immediately if you have pain in your shoulder, especially when you lie down or if you show any signs of shock (clammy skin, weak pulse, dizziness) because these are symptoms of a ruptured ectopic pregnancy.
A miscarriage is the spontaneous loss of a pregnancy before the 20th week, but most miscarriages occur in the first trimester. According to the Mayo Clinic, most miscarriages result because the fetus has not developed normally. By the end of the first trimester all of the organ systems have formed and the likelihood of miscarriage decreases.
If you have vaginal bleeding along with cramps in your abdomen or back, and fluid or tissue coming from your vagina, you have probably miscarried and you will need to see your doctor soon. Spotting or bleeding early in pregnancy is very common and by itself does not mean you are having a miscarriage.