Twin Pregnancy: Everything You Need to Know

So you found out you’re pregnant with twins or know someone who is? Congratulations! You have lots of double fun to look forward to! But what exactly does twin pregnancy feel like, and what can you expect along the journey from conception to childbirth? Twins account for about 31 out of every 1,000 births, according to recent statistics from the Centers for Disease Control and Prevention (CDC). Due to the prevalence of IVF treatments and, because moms having babies at more advanced ages contributes to a higher likelihood of having twins, twin pregnancies have become more common.

Below, we will break down the most common types of twin pregnancies and cover information related to twin pregnancy belly, twin pregnancy nutrition, twin pregnancy symptoms versus singleton, possible complications of twin pregnancy, and mental health during twin pregnancy.

Twin Pregnancy: What You Need to Know

According to Johns Hopkins Medicine, a twin pregnancy consisting of two placentas and two amniotic sacs (one for each baby) is the optimal type of twin pregnancy. This is because each baby has its own protected space in which to grow, each has its own source of nourishment, and there is less risk of complications overall. This type of pregnancy is called a dichorionic-diamniotic (DCDA) twin pregnancy. There are two types of DCDA twins: dizygotic (fraternal) and monozygotic (identical). Twins that share a placenta (and may or may not also share an amniotic sac) are called monochorionic twins. Monochorionic twins are always identical and can be divided into two categories: those that share a placenta but have two separate amniotic sacs are called monochorionic-diamniotic (MCDA) twins¹. In contrast, those babies that share a placenta and an amniotic sac are monochorionic-monoamniotic (MCMA) twins².

Important Twin Terms

• Di: means “two”
• Mono: means “one”
• Chorion/-chorionic: refer to the outermost fetal membrane that turns into the placenta, which provides the twins with nourishment³
• Amnion/-amniotic: the innermost fetal membrane that forms a sac filled with a protective fluid⁴
• Zygote/-zygotic: the cell that forms from the fusion of a sperm and egg and eventually develops into the fetus⁵
• Identical: Also called “monozygotic,” these are twins that separate from one zygote and develop into two fetuses of the same sex with identical genetics⁶. Identical twins occur at random, not by genetics.
• Fraternal: Also called “dizygotic,” these are twins that result from two separate fertilized eggs and develop into fetuses with separate or partially fused chorionic sacs (placentas)⁷. Fraternal twins have a genetic component and are more common than identical twins.

Different Types of Twin Pregnancy

Dichorionic-Diamniotic Twins (DCDA) 

A dichorionic-diamniotic twin pregnancy⁸, or DCDA, is one in which two fetuses each have a separate chorion (placenta) and separate amniotic sac. The placentas can be totally separate from one another or fused together. DCDA twins can be identical or fraternal.

Key takeaways:

• 2 separate chorions (placentas)
• 2 separate amniotic sacs
• Can be monozygotic (identical) or dizygotic (fraternal)
• The placentas may be completely separate, or placentas may be fused

Monochorionic-Diamniotic Twins (MCDA)

A monochorionic-diamniotic twin pregnancy⁹, or MCDA, is one in which a single fertilized egg splits into two identical clones, which go on to share the same chorion (placenta) but have separate amniotic sacs.

Key takeaways:

• One shared chorion (placenta)
• 2 separate amniotic sacs
• Monozygotic (identical)

Monochorionic-Monoamniotic Twins (MCMA)

A monochorionic-monoamniotic¹⁰ twin pregnancy, or MCMA, entails having twin babies growing in one sac and sharing a single placenta. It’s uncommon and affects a very small percentage of all twin pregnancies. MCMA twin pregnancies sometimes have a higher risk of complications, including miscarriage, stillbirth, fetal anomalies, and cord entanglement.

Key takeaways:

• One shared chorion (placenta)
• One shared amniotic sac
• Monozygotic (identical)
• Higher risk of complications
• Extremely rare

Twin Pregnancy Belly

A twin pregnancy belly will feel different for every mom, but you can generally expect to grow a larger bump than the one you have for a singleton pregnancy. The amount of weight each mother gains should depend on her body mass index (BMI) before pregnancy, height, and body type. According to the American College of Obstetricians and Gynecologists (ACOG), most women carrying twins are advised to gain 37-54 pounds.

Additionally, weight gain is significant during the early stages of placenta development and at weeks 20-24. The size of your belly may also be determined, in part, by whether or not it’s your first pregnancy or a second or subsequent pregnancy, the amount of amniotic fluid, and the change in your baby’s position, which can affect the shape of your tummy.

Nutrition for Twin Pregnancy

According to the American College of Obstetricians and Gynecologists (ACOG), if you’re pregnant with twins, you need about 600 extra calories a day or 300 calories per baby. Be sure to eat a diet rich in protein, Vitamin B12, Iron, Calcium, Vitamin D, essential fatty acids, and folic acid.

Brigham and Women’s Hospital recommends the following nutritional guidelines:

• Protein: 100 grams per day.
• Calories: 300 per baby per day, so 600 calories per day for twin pregnancies. This amount may need to increase during your pregnancy, so check with your healthcare provider.
• Iron: 30 milligrams per day in the first trimester and 60 mg per day second and third trimesters. This helps prevent anemia. Check to see if your existing prenatal vitamin includes iron. If not, you can use an iron supplement.
• Folic acid: 1 mg per day is recommended to prevent birth defects of the brain, spine, or spinal cord, and most prenatal vitamins have 0.4 to 0.8 mg of folic acid, which may not be enough.

Here are some great prenatal vitamins that are highly recommended!

Twin Pregnancy Symptoms vs. Singleton Pregnancy

Weight Gain

You’re likely to gain more weight with two babies than one, though the exact amount of weight a mother gains will depend on her height and body type. The weight gain is due to your natural need to consume more calories to feed your babies, resulting in increased blood volume, a growing uterus, and an overall slightly higher weight gain than mothers carrying only one baby.

Worse Morning Sickness

Some moms with twin pregnancies report having worse nausea and being more sensitive to food smells than when they were only pregnant with one child. This is likely due to heightened sensitivity from the increased presence of hormones in your body.

Breathlessness

Shortness of breath is a symptom in pregnancy but may be more pronounced if you’re carrying twins. Two babies instead of one are pushing against your diaphragm, and your body is pumping more hormones. Other causes can be asthma or anemia, which is a depletion of oxygen-carrying red blood cells. Anemia can be checked by your healthcare practitioner and can be remedied by iron supplements. If your breathlessness is constant, you have chest pain, a rapid pulse, or notice your lips or fingertips look bluish, contact a doctor immediately.

Fatigue

If you notice you are feeling exhausted and regular daily activities cause you to fatigue easily, you may be carrying twins. Most symptoms that women experience in a singleton pregnancy are exaggerated with a twin pregnancy.

Early Quickening

Some moms report feeling the sensation of their babies moving inside the womb as early as 16 weeks. With single babies, such movement or “quickening” is typically experienced by 22 weeks.

Possible Complications for Twin Pregnancy

According to Brigham and Women’s Hospital, if you’re pregnant with twins, you and your baby may be at higher risk for the following complications.

Twin Pregnancy Complications in Moms

• Gestational diabetes is more common among mothers expecting twins because the larger placentas produce more pregnancy hormones. Medical treatment is available to help control maternal blood sugar, and the condition is usually temporary and goes away after pregnancy.
• Hypertensive disorders can develop in the second half of pregnancy. High blood pressure (hypertension) or preeclampsia treatments can include medication, increased monitoring, hospitalization, or early delivery.
• Anemia is a low red blood cell count and may occur due to the twins’ high nutritional demands on the mother’s body. These cases are typically mild and treated with iron supplements.
• Low back pain and sciatica are more common during twin pregnancy due to the added strain of having two babies. Pain can often be relieved through prenatal massage, acupuncture, chiropractic care, stretching, and other natural remedies, such as a foam roller.
• Gastroesophageal reflux disease (GERD), or heartburn, can be treated by a change in diet, specifically less acidic foods and more soothing foods such as yogurt, which has the added benefit of probiotics. Heartburn during pregnancy can also be treated with most over-the-counter (OTC) heartburn medications, but always consult your medical provider first.

Twin Pregnancy Complications in Babies

• Preterm birth is one that happens before 37 weeks and is the most common complication to navigate for a twin pregnancy. Babies born prematurely will likely need to be tended to in the Neonatal Intensive Care Unit (NICU) before going home.
• Intrauterine growth restriction (IUGR) is a risk for twins because of competition for placental nourishment, resulting in one fetus weighing less than the other. Most cases of IUGR are mild and don’t result in any complications.
• Twin-to-twin transfusion syndrome (TTTS) occurs in monochorionic twins, which is when twins share a chorion, also called a placenta. With only one placenta between them, if the network of blood vessels that supply oxygen and nutrients is not spread evenly, there is an imbalance between the twins. The donor twin gives away more blood than it receives and can be at risk of malnourishment and organ failure, while the recipient twin gets too much and can be subject to cardiac risks. TTTS is diagnosed using an ultrasound that can measure the twins’ amniotic fluid volume and determine whether or not there is an imbalance.
• Selective growth restriction is a higher risk for monochorionic twins and results in twins differing in size by more than 20%, with one of the twins being considerably growth restricted.
• Twin anemia polycythemia sequence (TAPS) is a relatively newly described monochorionic twin complication, according to the Fetal Institute located in Miami, Florida. It may coexist alongside TTTS but can also occur on its own. The disorder is defined by blood hemoglobin differences between twins due to a slow transfusion of blood from the donor twin to the recipient twin through very small arteriovenous vascular anastomoses. There is no significant difference between the twins in size or volume of amniotic fluid, and the disorder must be diagnosed by ultrasound.
• Cord Entanglement is a risk factor in monochorionic monoamniotic (MCMA) twins. Umbilical cords may become entangled since MCMA twins share an amniotic sac, increasing the risk that cords will become compressed, affecting blood flow to either twin.

Twin Pregnancy Mental Health

If you are a mom experiencing a twin pregnancy, you may feel a combination of different emotions! However, expecting mothers can also experience anxiety and depression. Luckily, there are a lot of treatments available, including talk therapy, professional counseling, support groups, and medication options. Staying mentally well is important when pregnant with twins, as depression and anxiety can get in the way of taking care of yourself and your growing twins. If you are experiencing regular feelings of sadness, anger, guilt, anxiety, or have lost interest in doing things that you used to enjoy, talk to your medical provider for psychological support options.

References

1. https://www.obgyn.columbia.edu/patient-care/our-centers/center-prenatal-pediatrics/conditions-we-care/monochorionic-diamniotic-twins

2. https://www.obgyn.columbia.edu/patient-care/our-centers/center-prenatal-pediatrics/conditions-we-care/monoamniotic-twins

3. https://www.medicinenet.com/chorion/definition.htm

4. https://medical-dictionary.thefreedictionary.com/amnion

5. https://www.medicinenet.com/zygote/definition.htm

6. https://medical-dictionary.thefreedictionary.com/identical+twins

7. https://www.britannica.com/science/dizygotic-twin

8. https://www.ncbi.nlm.nih.gov/medgen/755988

9. https://obgyn.onlinelibrary.wiley.com/doi/10.1002/pd.5705

10. https://samitivejhospitals.com/article/detail/monochorionic-monoamniotic-mcma-twins