Twins, Triplets, or More

A “twins or more” pregnancy may also be called a multiple pregnancy or a multiple gestation.  This means that a mother is pregnant with more than one baby at the same time. There are two types of twins:  identical and fraternal.

How do twins and triplets or more happen?

Identical twins happen when one egg is fertilized by one sperm but divides after it is fertilized to produce two unborn babies with the same genes.  As a result, identical twins are always the same sex.  Fraternal twins happen when two eggs, instead of just one, are produced in the woman’s ovaries during the same menstrual cycle.  Both eggs are then fertilized by two different sperm.  The unborn babies may be the same sex (boy/boy or girl/girl) or the opposite sex (boy/girl).  Triplets or greater can be identical or fraternal twins or a mix of individually fertilized eggs and/or identical twins.  Having more than one baby in the womb is not very common, but occurs about 32 per 1,000 births.

Additionally, if a woman uses assisted reproductive technology (ART), or uses technology to get pregnant, and more than one fertilized egg is implanted, this will increase her risk for having more than one baby in the womb.  To reduce the risk of having more than one baby, a woman using ART should choose to have one fertilized egg implanted in the womb.

Are there risks to the mother or babies with twins, triplets or more?     

A pregnancy with more than one baby is a high-risk pregnancy.  It puts the mother at risk for having serious problems during her pregnancy.  The following can be problems for any mother – but carrying twins or more during pregnancy increases these risks:

  • High blood pressure
  • Anemia (low iron in the mother’s blood)
  • Preterm labor (going into labor before 37 weeks of pregnancy)
  • Breaking her bag of water more than 24 hours before delivery and/or more than two weeks before her due date
  • Severe nausea and vomiting causing dehydration that may require IV fluids
  • The placenta [afterbirth] growing over the opening of her uterus (also known as placenta previa).  This may allow the placenta to deliver before the babies are born.  It can cause severe bleeding in the mother and a loss of oxygen to the babies
  • Too much fluid in her bag of water

The following problems can happen at the birth of any infant, but twins or more increases these risks:

  • The mother may need a Cesarean section delivery (delivery through an opening the doctor makes in the mother’s abdomen)
  • The placenta may separate from the wall of the uterus before the infants are delivered.  This can cause a loss of oxygen to the babies
  • The babies’ cords may become tangled in the uterus or a cord may deliver in front of the baby.  This pinches off the baby’s umbilical cord and blocks oxygen from reaching the babies in the uterus
  • The mother may get an infection in her uterus after delivery of the babies.

Below are problems that can happen to all babies but those that are born as twins or more have increased risk for:

  • Delivering too soon (giving birth 3 or more weeks before the due date)
  • The babies being born at a low birth weight (less than 5 pounds 8 ounces) or at a very low birth weight (less than 3 pounds 5 ounces)
  • Weighing less than most babies born at the same stage of pregnancy even if the babies are born near their due date
  • Twin to twin transfusion (oxygen and nutrients in the blood only go to one baby and not both)

How can I have a safe pregnancy if I have more than one baby in my pregnancy?

Having a healthy pregnancy with more than one baby in the womb can be achieved by going to the doctor early in your pregnancy and attending all scheduled prenatal visits.  When you have more than one baby, it is important that the doctor monitors your pregnancy closely.  You may require additional or more frequent testing than if you only had one baby during your pregnancy.   It is possible to have a safe pregnancy and delivery with one or more babies in the womb, but it is important to be aware of the increased risks that go along with having more than one baby in your pregnancy.