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Multiple Gestation

High-Risk Obstetrics, Multiple Gestation Risks, Menopause Center of Los AngelesMultiple gestation (or multiple pregnancy) is when a woman is pregnant with more than one fetus. She may be expecting twins, triplets, or more.

Two Types of Multiple Pregnancies


When more than one fetus originates from the same egg, we call them identical. A single egg is fertilized by a single sperm, and then the egg spontaneously splits into two genetically identical embryos. It’s not clear why this happens, and there’s no correlation between the likelihood of having identical babies and your race, age, or family history.

Identical babies will all be the same sex, and will have the same blood type. Although identical twins usually look very much the same (same eye and hair color, body type, etc), they don’t always look 100% identical. Many other factors play a role in shaping your child’s appearance. They’ll even have their own unique fingerprints!


When two or more eggs are fertilized by more than one sperm, the resulting babies are fraternal. Unlike identical pregnancies, fraternal pregnancies do run in families. If any relatives on your mother’s side had fraternal twins, the chances that you will have them too are greater. Fraternal pregnancies are also more common in women over 35, women of African descent, and women who have just quit taking birth control pills.

Although fraternal babies are very similar to each other due to having the same parentage, they are genetically different, and will likely resemble each other as much as ordinary brothers and sisters do. Fraternal babies can be both sexes and may have different blood types.

Fertility Treatment and Multiple Gestations

High-Risk Obstetrics, Multiple Gestation Risks, Menopause Center of Los AngelesWomen undergoing fertility treatment are much more likely to have a multiple gestation than other women. This is because fertility drugs boost your fertility potential by causing your ovaries to release multiple eggs at a time. This raises the odds that more than one egg will be fertilized in the same cycle.

With in-vitro fertilization, it’s common practice for the doctor to place more than one fertilized egg in the uterus at a time, to increase the chances that at least one will implant and gestate to term. Of course, this also increases the likelihood of a multiple gestation.

Are Multiple Gestations Riskier than Single Pregnancies?

Modern medicine has done wonders for increasing the safety of multiple pregnancies, but they still carry some risks. Carrying more than one baby increases the chances of:

  • Pre-eclampsia. This is a disease which raises your blood pressure to dangerous levels.
  • Gestational diabetes. This is a type of diabetes that affects pregnant women.
  • Pre-term delivery. Multiple babies are more likely to be born prematurely, which hinders their development and puts their health at risk.
  • Birth defects. Certain genetic disorders are more common in multiple gestations.
  • Miscarriage of one or more of the fetuses.

Although these conditions are more common with multiple pregnancies than single pregnancies, most women carrying multiples have uncomplicated pregnancies that result in safe births, and healthy children.

What Should I Expect With a Multiple Gestation?

If you are carrying twins, triplets, or more, your gynecologist will be able to detect them during a routine ultrasound. You may be able to hear more than one heartbeat, and go home with a sonogram that shows each of your fetuses. Your doctor will also be able to tell you if they’re healthy, and developing as expected.

Your OB-GYN will probably want to see you more often with a multiple pregnancy than with a single pregnancy. You will need more frequent ultrasounds and other tests to check up on the babies’ progress, and catch any problems that may arise.

Carrying more than one fetus is harder on your body, and so your doctor will want to check up on your health as well. You should expect regular blood and urine tests, and careful monitoring of your blood pressure.

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