Multiple Births: Everything You Want To Know

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In the US in 2014, almost 34 out of a thousand deliveries were twins. That’s more than 135,000 sets of twins! While the basics of pregnancy are the same, multiple births also come with unique risks – and an extra large belly! Here’s what you need to know about multiple births:

Types of Multiples

When we think of multiple births, we most commonly think of twins and triplets. Twins are by far the most common compared to larger numbers multiples. Triplets make up just 0.01% of live births in the US. Higher-order multiples (HOMs) also happen, but are even less common. In 2014, there were 246 quadruplet births and 47 births with 5 or more babies.

In general, there are two types of multiples: identical and fraternal. Identical multiples happen when one fertilized egg splits completely in half, meaning two separate zygotes with the same genetic material form. Identical multiples are always the same sex (barring certain rare genetic anomalies). Fraternal multiples, on the other hand, grow from two separate eggs fertilized by two separate sperm. Essentially, they’re like any other siblings but born at the same time. That means they have their own unique genetic material and may be of mixed sex. In fact, male-female fraternal twins are the most common type, accounting for about 40% of all twins!

There are also several different ways multiples can be arranged. Singletons have a single placenta and a single amniotic sac. Multiples, on the other hand, may share one or both of those. There are three possible combinations for twins:

• dichorionic-diamniotic: each twin has a separate placenta and amniotic sac; possible for both identical and fraternal twins
• monochorionic-diamniotic: twins share one placenta but have separate amniotic sacs; almost always identical twins, although there are exceptions
• monochorionic-monoamniotic: twins share the same placenta and amniotic sac; always identical twins

So, almost all fraternal twins have their own placentas and amniotic sacs. Identical twins are more likely to have separate placentas and/or amniotic sacs if they separate very early in the pregnancy. If separation happens less than three days after fertilization, dichorionic-diamniotic is most likely. If separation happens in under a week, monochorionic-diamniotic is likely. After that, monochorionic-monoamniotic is most likely.

With triplets and HOMs, things can get a little more complicated. For example, you may have a set of triplets consisting of one singleton and one set of twins. You could have three separate placentas (multichorionic) and amniotic sacs (multiamniotic), but you could also have a set of twins that share both and a separate singleton. You could also have monochorionic-monoamniotic triplets (this is very rare). The more multiples you have, the more possible combinations there are.

Conjoined Twins

Conjoined twins only occur once in every 200,000 births in the US. Conjoined twins’ skin, bones, and/or organs are fused together. This condition usually occurs when the fertilized egg separates a couple of weeks after conception and doesn’t separate completely. So, conjoined twins are always identical.

The most common types of conjoined twins are “thoracopagus” twins, accounting for about 40% of all conjoined twins. They’re connected at the torso and share a heart. “Omphalopagus” twins account for about 33% of cases: they’re joined at the lower torso and may share a number of abdominal organs.

Conjoined twins are prone to serious health problems. About half are stillborn and another 35% pass away within a day. Overall, fewer than 25% survive. Some conjoined twins may be separated but others are too closely linked for that kind of procedure.

Risks And Precautions For Multiple Births

Pregnancy is already pretty complicated – there’s a lot of development and growth that has to happen. When you have two or more little ones developing at the same time, complications are more likely. And the higher the number of multiples, the higher the risk.

1. Preterm Birth

The most common complication is premature birth, usually because of “preterm premature rupture of the membranes” (PPROM). In other words, your water is likely to break early if you’re pregnant with twins or HOMs and at that point, you have to deliver. Single pregnancies last an average of 39 weeks while twin pregnancy last an average of 36 weeks. Triplets average 32 weeks while quads and quints average 30 and 29 weeks, respectively. Full term is 40 weeks and the earlier the birth, the higher the risk of serious complications. Preterm babies may not have fully-developed lungs or hearts and may need a ventilator or other medical intervention.

2. Low Birth Weight

Multiple births come with a higher risk of low birth weight. Babies with a low birth weight are called “SGA” (small for gestational age). SGA babies are at a higher risk for complications like asphyxia, meconium aspiration, and hypothermia during and after delivery. That can lead to long-term medical conditions, including cerebral palsy.

In many cases, the low birth weight associated with multiple births is caused by intrauterine growth restriction (IUGR). A single baby is taking up a lot of resources by the time you hit full term. With multiples, there may simply not be enough to go around! If the blood flow from the placenta(s) isn’t strong enough, that can slow down your little ones’ growth.

3. Preeclampsia

Preeclampsia, or pregnancy-induced high blood pressure, is a potentially life-threatening medical condition. It can cause damage to the mother’s brain and other organs and increases the risk of complications during delivery. Women expecting multiple births are more than three times as likely as women with singletons to develop it. In addition, preeclampsia tends to be more severe in women carrying multiples.

One of the most serious risks associated with preeclampsia is placental abruption, where the placenta detaches from the wall of your uterus too early. Mild cases, where only a small part of the placenta separates, may just require monitoring. More severe cases will require immediate delivery – it can cause life-threatening bleeding otherwise.

You should seek immediate medical attention if you experience any of the symptoms of preeclampsia.

4. Twin-Twin Transfusion Syndrome

Monochorionic twins (those that share the same placenta) are at risk for twin-twin transfusion syndrome – where one baby gets more blood flow than the other. Generally, it happens because abnormal blood vessels direct more blood to one baby than the other. That puts a serious strain on the heart of the baby that’s getting extra blood and can result in too much amniotic fluid. The baby that’s getting less blood may have slower growth and a shortage of amniotic fluid.

Mild cases may just require monitoring or removal of some of the excess amniotic fluid. More severe cases may require laser surgery to seal off the abnormal blood vessels. Preterm birth is more likely for babies suffering from twin-twin transfusion syndrome.

In some cases, emergency surgery may be required to deliver the babies. This condition can be fatal to one or both children. It affects about 15% of identical twins; you should contact your doctor immediately if you feel a sudden growth in your uterus or if your belly is unusually large for your stage of pregnancy. Your doctor may also identify this condition during routine ultrasounds and exams.

5. C-sections

Multiple births are more likely to require a c-section for delivery. Vaginal delivery is possible if the babies are in the right position and is even fairly common for twins. To deliver twins vaginally, the baby closest to the exit must be head down and the second baby must be smaller than the first. You’ll also need to be past 32 weeks. Triplets and HOMs are generally delivered by c-section. They tend to be more premature, meaning they’re less able to withstand the stresses of labor and delivery. They may also be premature enough that they need immediate medical support. Finally, it’s unusual for three or more babies to get themselves into the right position for delivery.

6. Birth Defects

Multiples are twice as likely to have birth defects compared to singletons. They’re more likely to be premature, which increases that risk. They’re also more likely to have low birth weight and the deprivations associated with twin-twin transfusion syndrome may mean they don’t have the nutrients they need to develop normally.

Risk Factors For Multiple Births

A number of factors can increase the likelihood of multiple births:

• A family history of multiple births (especially on your mother’s side) increases your likelihood of having multiples.
• The likelihood of multiples increases the older you are and the more children you’ve had before. For example, women over 35 that have had 4 other children are 3 times as likely to have multiples as a childless woman under the age of 20.
  • Just 2% of teenage pregnancies are multiples, compared to 6% of women over 40
• A high-fat diet increases the likelihood of multiples.

One of the most important factors is whether you’ve used IVF or other fertility treatments. As many as 1/3 of women using fertility treatments may have multiples, depending on the treatment.

Multiple births have increased significantly over time – increasing by 75% since 1980. In large part, that’s due to the rise of fertility treatments and the increasing average age at which women have children. As fertility treatments improve and advance, multiple births associated with those treatments are becoming less common.

What Multiple Births Mean For Your Pregnancy

Most of the time, your doctor will determine that you’re pregnant with twins or HOMs within the first trimester. Depending on your health, family history, and the number of babies, placentas, and amniotic sacs, you may need extra checkups. You’ll also need to talk to your doctor about extra nutritional supplements and dietary needs and what kinds of exercise are safe. As you approach term, you may need bed rest to help extend your pregnancy as long as possible.

Note that multiples conceived with IVF are at a higher risk than naturally-conceived multiples for complications and may require additional monitoring.

Are You Expecting Multiple Births?

Congratulations! This is exciting! And the trick to managing it is taking the best possible care of yourself. Keep in close contact with your doctor and report any unusual symptoms or anytime you feel like something is off. We’ve said it before and we’ll say it again – you know your own body and you shouldn’t ignore it. If your own doctor doesn’t address your concerns, find a second opinion.

Multiple births mean you’ll have your hands full, so make sure to seek out support from friends and family to help you manage it. If you need support, there are a number of organizations that may be able to help, including your local WIC agency, the Maternal and Child Health Bureau, Head Start, and others. These and other local organizations can help you afford your medical care and childcare costs and connect you with childcare options.

Did you have a multiple birth? Tell us about it in the comments!

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