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Conception of identical twins

Twin-to-twin transfusion syndrome

Multiple-Birth Pregnancy

Under natural conditions, your chance of having a pregnancy with more than one baby is relatively low (approximately a 1.5% chance). However, the number of multiple births has increased dramatically over the past 15 years. There are two specific reasons contributing to this increase. The first one is the use of fertility drugs and in-vitro fertilization. The second is the increase of pregnancies in older moms, who have an increased likelihood of multiple birth pregnancy.

However, in the last 10 years, single embryo transfers have become more common than in the past in women using IVF. This has resulted in more singleton births, and fewer multiple birth deliveries including twins, triplets, and quadruplets. However, multiple births are still more common in IVF pregnancies than in naturally conceived pregnancies.

Fraternal Or Identical Twins

There are two types of twins, fraternal and identical. Fraternal twins are more common because each baby develops from a separate egg and sperm. Generally, the ovaries release one egg a month, but sometimes more than one egg is released and fertilized. Fraternal twins will have individual placentas and amniotic sacs. Since each has a different egg and a different sperm, it is like siblings being born at the same time.


Identical twins come from one fertilized egg that splits early in the pregnancy and develops into more than one fetus. Identical twins will share the same genetic material, but depending on how soon after fertilization they split, they can also share the same placenta, membranes, or sac. Very rarely, the embryo can split late and result in conjoined twins. Because twins share the same genetic material, they have the same hair color, eye color, sex, and blood type.


How Will I Know I Have A Multiple Pregnancy?

Today, most multiple pregnancies are discovered long before delivery. Some signs and symptoms that may make you and your health care provider suspicious include:

  • Family history of fraternal twins
  • Larger uterus than expected
  • Use of fertility drugs
  • Extreme nausea and vomiting in early pregnancy (from increased levels of pregnancy hormones)
  • More than one heartbeat!

Generally, if multiple pregnancies are suspected, an ultrasound will be done to confirm it.

What Can I Expect?

Having more than one baby puts you at a greater risk for developing problems during the pregnancy, as compared with a single-birth pregnancy (one baby). All multiple pregnancies are considered high risk ("special care") and will be treated as any other high-risk pregnancy.

You can expect to see your health care provider more often than if you were just carrying one baby. More ultrasounds will be done in order to make sure there is enough room for the babies, and that they are growing at the same rate throughout the pregnancy.

You are at a higher risk for maternal and fetal complications, so you will be more closely monitored overall.

Having a multiple pregnancy may make you more uncomfortable, because you will gain more weight than with one baby. Your uterus will become much larger, and this may place more pressure on the other organs earlier than in a single-birth pregnancy.

You may experience symptoms earlier and more intensely. Some of these include:

  • Constipation
  • Shortness of breath
  • Heartburn
  • Urinary problems
  • Back pain
  • Hemorrhoids
  • Pelvic pain

As your pregnancy progresses, the physical discomfort may prevent you from continuing to work as long as you had planned. In more extreme cases, it may even require hospitalization for several weeks before you are ready to deliver. However, some women have no more problems than with a normal pregnancy.

What Are The Risks?

Multiple birth pregnancies put more of a strain on your body and your uterus. Two or more babies mean a bigger placenta and higher levels of circulating hormones. These changes can lead to more pregnancy complications.

With a multiple pregnancy, you're at higher risk of any of the following problems:

Some of the increased risks to the babies include:

  • Preterm delivery
  • Slowed growth of babies
  • Low birth weight or unequal size
  • Birth defects or death of one or more babies

If you're expecting three or more babies, you may wish to talk with your doctor about selective reduction. Carrying triplets or more puts you at high risk of miscarriage or extremely preterm delivery, with long-term health problems for all of your babies. Some women choose to abort one or more of the pregnancies to reduce the risk of very early delivery for all three or four. This is a very difficult decision to make, and you should discuss the risks and benefits in detail with your doctor and your partner.

How Can I Take Care Of My Babies And Myself?

For many women expecting multiple babies, they experience the typical discomforts of pregnancy, but the discomforts may be more intensified. As with any pregnancy, eating right, getting enough rest, and going to your scheduled doctor appointments is the best way that you can take care of yourself and your babies.

Following the recommended pregnancy nutritional guidelines will be helpful. Your doctor will give you additional recommendations for vitamins and minerals, and probably an increased caloric intake that you may need when carrying more than one baby.

You will need to get enough rest and sleep. Physical exercise should be discussed with your doctor. The recommendations for exercise will probably change as you get closer to delivery.

Make sure you are also nurturing your emotions during this time. Your partner may be able to help you by giving you a nice massage, or stand by while you take a warm bath to help you out of the tub.

Try to ease any emotional stress you may be feeling, especially as the due date approaches and you prepare for the delivery and care of more than one baby. Speak to a health care professional if you are feeling extreme levels of anxiety

What Can I Expect During Labor And Delivery?

With more than one baby to deliver, the chances of needing a C-section are greater. The decision generally will be based on the positioning of the babies. If the babies are headfirst, there is a greater chance that you may be able to deliver them vaginally. Some doctors feel more comfortable than others in delivering twins vaginally, especially if the first baby is headfirst and the other is breech (feet first). Others will attempt a series of maneuvers to turn the baby to the headfirst position in the uterus so that both can be delivered headfirst. If the first baby is feet first, you will need a c-section.

If the first baby is head down, keep in mind that there's a chance your first baby will deliver vaginally, and you will then need a c-section for the second baby. This is more likely if the second baby is breech (feet first) or if the second baby is larger than the first. Talk to your doctor about your risk of this "total obstetrical experience" Some mothers may prefer to have a c-section and skip labor altogether, while others want to try for a vaginal delivery. There's no single right answer - it depends on what feels most comfortable for you and your partner.

You will want to discuss all these possibilities with your doctor in order to understand the various scenarios that may take place on your delivery day. Recognize that even with all the discussions and planning prior to the actual event, there is still a chance that the plans may change on that special day!

Review Date: 7/4/2019
Reviewed By: John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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