Over the past two decades, there's been a phenomenal rise in the number of multiple births in the United States. Between 1980 and 2004, the number of twin births increased by 70% and the number of births involving three or more babies has quadrupled.

What's responsible for this dramatic rise in multiple births? And how should you prepare for your own multiple birth experience?

The Miracle of Multiples

Several factors contribute to the development of a multiple pregnancy:

• Heredity: A history of multiple births on a woman's side of the family increases her chances of having a multiple pregnancy.
• Race: Women of African descent are the most likely to have multiple pregnancies.
• Number of prior pregnancies: Having more than one previous pregnancy, especially a multiple pregnancy, increases the chance of having a multiple pregnancy.
• Delayed childbearing: Older women who get pregnant are more likely to have multiples.
• Infertility treatment: Fertility drugs, which stimulate the ovaries to release multiple eggs, or assisted reproductive technology (ART), which transfers multiple embryos into the womb (such as in vitro fertilization, or IVF), greatly increase a woman's chance of having a multiple pregnancy.

It's the last two factors that have been on the rise in the last couple of decades and are probably responsible for the increase in multiple births.

The Types of Multiples

There are two types of twins: monozygotic (identical) and dizygotic (fraternal).

Identical twins result from a single fertilized egg dividing into separate halves and continuing to develop into two separate but identical babies. These twins are genetically identical, with the same chromosomes and similar physical characteristics. They're the same sex and have the same blood type, hair, and eye color.

Fraternal twins come from two eggs that are fertilized by two separate sperm and are no more alike than other siblings born to the same parents. They may or may not be the same sex. This type of twins is much more common, and only this type is affected by heredity, maternal age, race, and number of prior pregnancies.

"Supertwins" is a common term for triplets and other higher-order multiple births, such as quadruplets or quintuplets. These babies can be identical, fraternal, or a combination of both. But higher-order births are rare; triplets occur in approximately 1 in 7,000 to 8,000 births, whereas quintuplets are likely to be born only once in 47 million births.

The Risks of Multiple Births

The most immediate risk involved with multiple births is pre-term (or early) labor resulting in premature births. A typical, single pregnancy lasts about 40 weeks, but a twin pregnancy often lasts between 35 to 37 weeks. Nearly half of all twins are born prematurely (before 37 weeks), and the risk of having a premature delivery increases with higher-order multiples.

Premature babies (preemies) can have numerous health challenges. Because the care of premature babies is so different from that of full-term infants, preemies are usually placed in a neonatal intensive care unit (NICU) after delivery. The risk of developing health problems increases with the degree of prematurity — babies born closer to their due date have a lower risk.

In addition to the possibility of premature births, other medical conditions that are more likely to occur during a multiple pregnancy include preeclampsia, gestational diabetes, placental problems, and fetal growth problems. Being part of a multiple birth can also be associated with long-term health problems in the infants. Developmental delays and cerebral palsy occur more commonly in twins than in single births, and there's a higher risk of enduring health problems with higher-order multiple births.

Because of these concerns, many doctors who specialize in fertility treatments require prospective parents to undergo intensive counseling on the possibilities and risks associated with multiple births.

Staying Healthy During a Multiple Pregnancy

Eating properly, getting enough rest, and making regular trips to the doctor are critical measures for any expectant mother to stay healthy. And a woman with a multiple pregnancy might be scheduled for more frequent appointments with her obstetrician/gynecologist (OB-GYN) than a women who is pregnant with a single fetus.

The need for frequent, intensive prenatal care is of the utmost importance in a multiple pregnancy. You'll want to be particularly careful about finding health care professionals who have experience with multiple births. Because multiple pregnancies are automatically termed high-risk, the need for specialized health care is vital to ensuring that you and your babies receive the best care available.

Because you may not know anyone who has experienced a multiple birth, asking for a referral from a friend may not be productive. Instead, ask your doctor or OB-GYN to recommend a facility that specializes in multiple births. You should be part of a pre-term birth prevention program at your hospital and have immediate access to a specialized NICU should you go into early labor or if one of your babies is born with a health problem.

Your Nutrition

If you're pregnant with multiples, you should follow general pregnancy nutrition guidelines, including increasing your calcium and folic acid intake. Pregnant women need additional calcium, so extra milk or fortified orange juice, broccoli, sardines, or other calcium-rich foods should be added to your diet.

As with all expectant mothers, folic acid is extremely important. Taking folic acid 1 month prior to and throughout the first 3 months of pregnancy will decrease the risk of neural tube defects (such as spina bifida).

Another dietary requirement that needs to be increased if you're expecting more than one baby is protein, which has several important functions. First, proteins serve as the building materials of body tissue. They also act as enzymes that regulate chemical reactions to keep a body growing and functioning.

During pregnancy, an increased supply of iron is also needed for hemoglobin, the substance in red blood cells that binds oxygen for delivery to the tissues. Insufficient iron can lead to a condition known as iron-deficiency anemia. Anemia occurs when the number of healthy red blood cells decreases in the body), and is relatively common in multiple pregnancies. Anemia can cause a decreased appetite and extreme fatigue during a pregnancy, as well as a reduced oxygen supply to the developing babies. Your doctor will probably prescribe an iron supplement, as your requirement for this mineral usually can't be met by diet alone.

Iron is absorbed more easily when combined with foods high in acid, such as yogurt, and those with high amounts of vitamin C, like orange juice.

Additional fetuses also mean an increased need for all other nutrients (such as zinc, copper, vitamin C, and vitamin D). So it's important to take your prenatal vitamin supplement every day. But just because you're carrying more than one baby doesn't mean you should take more than one prenatal vitamin — one is enough and too much can even be harmful.

Your Weight

Mothers carrying multiples are expected to gain more weight during pregnancy than mothers carrying a single fetus. But exactly how much weight you should gain depends on your pre-pregnancy weight and the number of fetuses, so make sure to talk to your doctor.

In general, though, you should consume about 300 additional calories a day for each fetus. It might be tough to eat a lot when your abdomen is full of babies, so try to eat smaller, more frequent meals.

Your Comfort

Of course, expecting multiples means that you're probably experiencing the typical discomforts of pregnancy more intensely. Nurturing yourself can help ease the stress of pregnancy. Even a warm bath can help lift your spirits. (Just make sure you have someone around to help lift you out of the tub!)

Expectant partners can help, too. Something as simple as having someone brush your hair can make the discomforts of pregnancy fade momentarily. It helps, too, if your partner remembers that your body is going through tremendous hormonal changes. Communication and understanding can be the keys to truly enjoying this special time in your lives.

Preparing for Childbirth

Getting ready for a multiple birth may seem overwhelming, and concerns about pre-term labor can be additional burdens for you to bear. The best reassurance is knowing that you have a network of support around you: capable doctors, a caring hospital staff, and hopefully a supportive partner, family members, and/or friends.

To help you be more comfortable with the birth process as it unfolds, you should also discuss the options of vaginal delivery versus cesarean section (C-section) with your doctor well before your due date. Several factors affect the safety of each approach. Even if you and your doctor agree to attempt a vaginal delivery, circumstances may arise during labor or delivery that make a C-section necessary.

You may opt to have additional birthing attendants in the room during labor and birth. For example, midwives are becoming more common. Working in collaboration with a medical doctor, a certified nurse-midwife (CNM) has specialized training in midwifery and is registered or licensed in all 50 states.

Hiring a doula is another option. The term comes from ancient Greece, where the doula was the primary attendant to the female head of the household. Today, doulas offer support services to women during the birth, as well as after delivery, by assisting with infant care and household chores.

Special Delivery

As labor begins, you'll likely be connected to a fetal monitor so your doctor can check each baby's progress. The interval between the birth of each baby delivered vaginally is usually less than an hour. And here's one piece of good news: Because multiple-birth babies tend to be smaller than single ones, it's easier to push them out. Luckily, they only come out one at a time!

In the case of multiples, though, a vaginal delivery may not always be possible. The crowded uterus can cause compression of the placenta or umbilical cord of any of the soon-to-be-born babies during labor. Prolonged compression may put one or more babies at serious risk as labor progresses during attempts at vaginal delivery. So prompt delivery by C-section may be necessary in these cases.

Positioning of the babies can also affect the safety of a vaginal delivery. It's common for the first baby to be born head first, whereas the subsequent infants may be breech (buttocks or feet first), transverse (sideways), or head first when entering the birth canal. Usually, if the first fetus is not head first, the babies will be delivered by C-section. And most triplets and other higher-order multiples are born by C-section.

If your doctor needs to perform a C-section, a catheter will be placed in your bladder, you'll be given anesthesia, and an incision will be made in your abdomen and uterus. The doctor will then deliver your babies through the incision. The babies will be delivered within just a few minutes of each other with this approach.

If you go into labor prematurely, you and your unborn babies will be closely monitored for signs of distress. You may have to make decisions on the delivery method and procedures at this time, so consider your options before arriving at the hospital.

Many babies born prematurely will need to go immediately to the NICU for the special care they need. Visitations by family members are usually encouraged, often right from the first day.

Taking Your Babies Home

The first days, weeks, and months are often the most difficult for parents of multiples, as everyone learns to get used to the frequent feedings, lack of sleep, and little personal time involved in parenting multiples.

Enlist whatever help you can get — from neighbors, family members, and friends — for household chores and daily tasks. Having extra hands around can not only make feedings easier and help you rest and recover from delivery, it can also give you the precious time you need to get to know your babies.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: November 2010