1. Identical twins occur when a single egg is fertilized by a single sperm to form one zygote but the zygote then divides into two separate embryos.
2. Non-identical twins occur when two or more separate eggs are fertilized by two or more separate sperms. They may have the same or different gender, appearance, and blood type.

You will need special prenatal care with twins. You should see your doctor more often and you may need special tests. Plan to take childbirth classes during your 4^th to 6^th month of pregnancy. Ask your doctor about classes for parents expecting twins.

When pregnant with twins, you will need to eat more than if you were carrying one baby. Eating well and gaining weight are important for your health and the health of your twins. Your body must nourish the babies and meet your energy needs as well. You will need to eat about 2,700 calories every day, if you are of average weight.

You should gain more weight when carrying twins than if you were having only one baby. Plan to gain 16-20 kilograms. In the last half of pregnancy, you should gain about 0.75 kilograms per week. If you are underweight, you may need to gain more. If you are overweight, you may need to gain less.

In addition to a prenatal vitamin, your doctor may prescribe extra vitamins and minerals to help your babies grow. Anemia (iron-poor blood) is more common in women who are pregnant with twins, so it's especially important to take your prenatal vitamins and iron as prescribed. Folic acid is also important for twins. It is hard to get all the folic acid you need just from your diet, so you should take a prenatal vitamin that contains folic acid. It is important to stop drinking alcohol, smoking, and taking illegal drugs during pregnancy.

Twins can make you more uncomfortable than usual during pregnancy because the uterus becomes much larger. Resting during the day will help give you energy. Some women may be asked to restrict their activity.

The risk of certain complications is higher in a twin pregnancy. The mother is more likely to develop high blood pressure or anemia, and the babies are more likely to be born small. The mother is also at increased risk for preterm labor. Sometimes these problems can be prevented with early detection and care.

Growth Problems
Twins are more likely to be smaller than average. Ultrasound is often used to determine the growth and the amount of amniotic fluid of each baby.
 
Monitoring a Twin Pregnancy
Many techniques are used to determine the well-being of your babies. Your doctor may use some or all of these techniques to monitor your babies:

• Ask you to count your babies' movements, called kick counts, at home.
• Examine your cervix by physical exam or ultrasound exam for changes that may show early signs of preterm labor.
• Repeat ultrasound exams to check the babies' growth.
• Measure the babies' heart rate in response to their own movements (non-stress test).
• Perform a biophysical profile, which includes checking the babies' heart rate, body movement, muscle tone, and the amount of amniotic fluid by ultrasound.

 
Having twins can be an exciting time. You can give your babies the best possible start by taking good care of yourself. Learn the warning signs of problems, and talk to your doctor or nurse about your questions and concerns.