Numerous complications may arise during pregnancy and childbirth. These situations include Rh factor incompatibility (a mother with Rh– blood giving birth to a child with Rh+ blood), ectopic pregnancy (implantation outside of the uterus), diabetes mellitus (high blood sugar) rubella (German measles), and eclampsia (high blood pressure and fluid buildup).

Pregnant women also experience numerous minor symptoms during pregnancy. A frequent symptom is morning sickness, which is characterized by early‐morning nausea, dizziness, and fatigue. The exact causes of morning sickness are unknown, but are probably due to hormonal changes in the woman's body. Such hormonal changes may also cause chloasma, or dark patches on the skin, which vanish early in postpartum. The stretch marks that appear on a woman's abdomen during pregnancy do not completely vanish but may turn lighter with time. Many pregnant women also suffer from stressed veins of the anus, or hemorrhoids. Hemorrhoids become uncomfortable as they itch, swell, or bleed.

Stillbirth and miscarriage

A stillbirth is the birth of a dead fetus after 20 weeks. A miscarriage is the spontaneous abortion of a nonviable fetus (one that is unable to live on its own) at less than 20 weeks gestation. Realistically, the number of miscarriages that occur every year is difficult to determine. As an example, a woman who does not realize she is pregnant may mistake a miscarriage for a menstrual period. Research, however, estimates that about 10 percent of pregnancies terminate in miscarriage. Chromosomal abnormalities are probably responsible for many miscarriages. In some cases, the ages of the mothers may also be a factor, as women over the age of 35 tend to have a higher incidence of miscarriages.

Premature birth

A premature, or preterm birth, a birth that occurs before a gestation of 37 weeks, differs from a stillbirth or a miscarriage in that the fetus is born viable (able to live outside of the uterus). Although many premature births are unexplained, some seem to be related to poor diet and alcohol or drug use during pregnancy, lack of prenatal care, and a history of premature births. The less an infant weighs at birth, the less chance it has of surviving.

Testing for disorders during pregnancy

Diagnostic tests are available for detecting potential fetal disorders and defects. An ultrasound examination (sonogram) involves bouncing high frequency sound waves off the fetus and transforming the bounced waves into visual images. During an amniocentesis test, a sample of the amniotic fluid is extracted by needle and is analyzed for fetal abnormalities such as fetal infections, chromosomal abnormalities, and other defects. Amniocentesis is performed no earlier than during week 15. Waiting until after week 15 helps the doctor avoid accidentally puncturing the fetus with the needle. Results of the amniocentesis are available within 1 to 2 weeks. Chorionic villi sampling tests for the same abnormalities as amniocentesis, though earlier (between weeks 9 and 14). In the placental covering are small villi, or thin blood‐containing extensions. A physician performs a chorionic villi sampling by inserting a catheter into the uterus through the vagina. Then, a small amount of fluid is suctioned out through the catheter. Results for chorionic villi sampling are available within just a few days.