A twin pregnancy comes with risks, both for the mother and the babies. Some moms hope to conceive twins, or even higher-order multiples, and will take active steps during fertility treatment to increase their odds. Other moms do what they can to avoid conceiving twins, but still get pregnant with more than one baby.
Understanding the risks of a twin pregnancy before you conceive can help you make decisions regarding your fertility treatment. For example, if your doctor offers a choice of transferring multiple embryos versus a single embryo during IVF treatment, you might be more willing to try a single embryo transfer (SET) if you know your risks. (Or, if your doctor doesn't even mention SET, you can ask if you're a good candidate for it, but only if you know your options.)
Understanding the risks of a twin pregnancy after you've already conceived twins is also important. For example, you can educate yourself on the signs and symptoms of premature labor, knowing prematurity is a risk with twins.
Not all risks are avoidable or within your control. Still, knowing what to watch out for can help reduce surprises along the way and increase your awareness of potentially troublesome symptoms.
Risks for the Mother During a Twin Pregnancy
Twin pregnancy is not just risky to the babies, but also to the mother. However, many of the risks to the mother are also risks to the unborn babies, since they can lead to premature labor, complications, or in the worst cases, fetal death.
Some of these risks are more of a nuisance than a real danger, while others can be life-threatening if left untreated.
- Pregnancy induced hypertension (PIH) is high blood pressure during pregnancy. As many as 37% of twin pregnancies involve PIH, which is three to four times the rate in singleton pregnancies. Left untreated, it can lead to premature labor, a baby who doesn't grow well, or a stillborn baby. It can also be a serious threat to the mother's health, especially if it develops into preeclampsia.
- Preeclampsia is a condition that includes both high blood pressure and protein in the urine. Symptoms may include swelling, severe headache, and rapid weight gain. It is twice as likely to occur in mothers of multiples. If left untreated, preeclampsia can lead to eclampsia, also known as toxemia. Eclampsia causes seizures and can be life-threatening to the mother and unborn babies. While blood pressure medications and anticonvulsant medications may stabilize the mother in severe cases, so the baby can spend a little more time in the womb, the only cure for preeclampsia is delivery of the baby.
- Gestational diabetes is a condition where a woman, who was not diabetic prior to pregnancy, has difficulty maintaining normal blood sugar levels. Gestational diabetes occurs in about 5% of singleton pregnancies, but women pregnant with twins are twice as likely to experience it. Gestational diabetes can usually be treated with diet and lifestyle changes.
- Mothers pregnant with multiples are more likely to experience problems with bleeding before or during delivery.
- Intense morning sickness is more likely in women pregnant with twins. For some, this is more of a nuisance than a danger, but some may develop hyperemesis gravidarum. Hyperemesis gravidarum is severe morning sickness, which leads to a 5% loss in body weight for the mother and may require hospitalization.
- Moms of twins are more likely to experience gastrointestinal problems during pregnancy, like constipation.
- If premature labor threatens, multiple pregnancies are more likely to require bed rest, which can lead to depression and job loss.
- If premature labor begins, the woman may need to take medications to stop labor and allow the babies more time in the uterus. These medications can have side effects, some mild and others more intense.
- Cesarean section is more likely with multiples, due to unfavorable presentation (such as when the first baby is not head down) or complications, which means longer recovery for the mother after birth and higher risk of complications during labor.
- Mothers of multiples are more likely to experience postpartum depression.
Risks for the Babies During a Twin Pregnancy
Twin pregnancies have a higher rate of miscarriage. In some cases, one twin may miscarry or simply "vanish," leaving a surviving twin. This is also known as Vanishing Twin Syndrome.
Twins are at risk for intrauterine growth discordance, which is when one twin grows significantly slower than another. In identical twin pregnancies, or pregnancies where twins share one placenta, this can be a sign of twin-to-twin transfusion syndrome (TTTS), where one twin takes more than its share of blood flow from the placenta. TTTS occurs in 10% of monochorionic pregnancies. If left untreated, severe TTTS can lead to infant heart failure or death of one or both twins.
Twins are more likely to have low birth weights, even when they are born on time. Twins are also more likely to become jaundiced.
Twin pregnancies have a higher risk for prematurity, which means birth that occurs after 20 weeks but before 37 weeks gestation. Just 40% of twin pregnancies go full term. The average twin pregnancy is 35 weeks, compared to the average singleton pregnancy, which is 39 weeks.
Prematurity may lead to a number of problems, including...
- Immature lungs, leading to difficulty with breathing. Premature babies may be put on ventilators until the lungs mature.
- Stomach and intestinal tract problems.
- Nervous system problems, including bleeding on the brain.
- Low birth weight.
- Feeding problems, including difficulty with breastfeeding.
Thanks to advances in technology, 90% of infants born after 28 weeks survive. However, even babies who survive prematurity are at risk for long-term effects. Long-term complications of prematurity may include...
- Bronchopulmonary dysplasia (BPD), a chronic lung condition that may require oxygen support for weeks or months after birth.
- General respiratory problems, including a higher likelihood of developing asthma and respiratory infections.
- Developmental delays.
- Learning disabilities, and in severe cases, retardation. This may not become evident for years.
- Cerebral palsy.
- Vision problems.
- Hearing loss.
Premature birth is also difficult for the parents, who go through the stress of having the babies in the NICU for days, weeks, or months, depending on how early the babies are born and what complications occur. Not being able to take your baby home can be very upsetting, and seeing your baby hooked up to the NICU equipment can be heartbreaking.
More on twins:
- What Increases My Chances of Having Twins?
- Positive Thoughts on Twins and Multiples
- Quiz: Are My Odds for Twins Higher Than Most?
- Twin Pregnancy Signs and Symptoms
- Quiz: Could I Be Pregnant with Twins?
- Clomid Twins: What Are the Odds You'll Conceive Twins?
David B. Schwartz, Yahya Daoud, Pauline Zazula, Gregory Goyert, Richard Bronsteen, Debra Wright, Joanna Copes. Gestational diabetes mellitus: Metabolic and blood glucose parameters in singleton versus twin pregnancies. American Journal of Obstetrics and Gynecology. Volume 181, Issue 4, October 1999, Pages 912-914.
Croft ML, Morgan V, Read AW, Jablensky AS. "Recorded pregnancy histories of the mothers of singletons and the mothers of twins: a longitudinal comparison." Twin Research and Human Genetics. 2010 Dec;13(6):595-603.
Chittacharoen A, Wetchapruekpitak S, Suthutvoravut S. "Pregnancy induced hypertension in twin pregnancy." Journal of the Medical Association of Thailand. 2005 Oct;88 Suppl 2:S69-74.
Trying to Get Pregnant. March of Dimes. Accessed February 3, 2012. http://www.marchofdimes.com/pregnancy/trying_multiples.html
McMullan PF, Norman RJ, Marivate M. "Pregnancy-induced hypertension in twin pregnancy." British Journal of Obstetrics and Gynecology. 1984 Mar;91(3):240-3.
Premature Birth. Center for Disease Control. Accessed February 3, 2012. http://www.cdc.gov/Features/PrematureBirth/
Premature infant. MedlinePlus. Accessed February 3, 2012. http://www.nlm.nih.gov/medlineplus/ency/article/001562.htm