7 Reasons Twins Are Born Early

Why Many Multiples Arrive Before Their Due Date

It's estimated that half of twins are born early, prior to 36 weeks gestation, which is almost a month before the standard 40 weeks gestation of a singleton baby. Triplets and other higher order multiples have an even greater chance of being born early. In some cases, the onset of preterm labor can not be halted, while in other situations, risks to the mother or babies require an early conclusion to the pregnancy.  Here are some of the most common reasons why twins are born early. 

Preterm Labor

Reasons why twins are born early
Preterm labor in twin pregnancy. Tetra Images / Getty Images

Early onset of labor is not uncommon in multiple pregnancies. Simply carrying multiple babies greatly increases the risk of preterm labor, so it's vital that expectant mothers of twins or more know the symptoms and seek appropriate medical care.  Some of the complications and conditions described below can prompt the onset of labor, but sometimes the exact cause isn't clear. But regardless of the reason, when the uterus begins to contract and/or the cervix begins to open in preparation for birth, the result is preterm labor. In some cases it can be suspended, but when it can not, the babies will be delivered prematurely and born early. 

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preeclampsia risk in multiple birth
Preeclampsia and early birth of twins.. Blend Images / Getty Images

 Many moms of multiples will encounter hypertension (high blood pressure) issues during her pregnancy, one of the most common complications of pregnancy. Preeclampsia is a disease characterized by high blood pressure combined with an elevated level of protein in the urine. Unchecked, it can cause serious medical issues for the mother, including seizures, stroke, and liver damage. Preeclampsia can be managed, but there is no cure except to deliver the babies. When preeclampsia cases sufficient maternal distress, early delivery of twins may be recommended. 

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Placenta Problems

pregnancy check placenta problems
Placenta problems and early delivery of twins.. JGI/Jamie Grill/Getty Images

With twins, there can be one or two placentas, which is the organ that sustains the babies during their time in the womb. It is attached to the interior of the mother's uterus and connected to the babies' via their umbilicaI cords. With the placenta(s) in multiple pregnancies covering a greater proportion of the uterine wall, there is a higher risk of complications that can be dangerous for mom or babies. Placental abruption, where the placenta detaches, or placenta previa, where the placenta is positioned low in the uterus, covering the cervical opening, are some situations that might prompt an early delivery.  

While placental problems like these can also impact singletons, Twin-to-Twin Transfusion Syndrome (TTTS) is a disease unique to twins. It occurs when abnormal blood vessels develop in a single, shared placenta, resulting in an unequal exchange of blood flow. In severe cases that compromise the babies, delivery may be an option. 

Ruptured Amniotic Membranes

Premature Rupture of Membranes (PROM) in Twin Pregnancy
Premature Rupture of Membranes (PROM) in Twin Pregnancy. Jose Luis Pelaez Inc./Blend Images/Getty Images

During pregnancy, the fetus -- or in the case of twins, fetuses -- is enclosed in a bag of fluid, in the amniotic sac. As a part of the labor process, the sac will break open (known as "water breaking").  But sometimes the sac ruptures early, known as PROM (Premature Rupture of Membranes) or PPROM (Preterm Premature Rupture of Membranes) if it happens prior to 37 weeks gestation. Once the bag of waters breaks, it presents an opportunity for infection if delivery isn't imminent, and may prompt an early delivery of twins. 

Mo-Mo Twins

Abdominal ultrasonography of monoamniotic twins at a gestational age of 15 weeks.
Abdominal ultrasonography of monoamniotic twins at a gestational age of 15 weeks.. Häggström, Mikael. "Medical gallery of Mikael Häggström 2014". Wikiversity Journal of Medicine

 A small percentage of monozygotic (identical) twins are identified as monochorionic-monoamniotic (Mo-Mo) twins. They not only share a single placenta but are also enclosed in a single amniotic sac. There is a danger of cord entanglement or cord compression in this situation, a serious situation which compromises the babies' survival. In some cases where this occurs, the best option for the babies is a premature delivery. 

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Growth Restriction

IUGR - Intrauterine Growth Restriction in Twins
IUGR - Intrauterine Growth Restriction in Twins. Westend61 / Getty Images

 IUGR -- or intrauterine growth restriction -- is a big group of letters that is used to describe a small problem with big consequences. That is, a baby or both babies that are too small and not growing sufficiently. In some twin pregnancies, one twin is impacted by IUGR while the other is not (known as Selective Intrauterine Growth Restriction or SIUGR). While twins are often born smaller than singletons, severe IUGR can present serious complications for an infant. Up to one-quarter of twin pregnancies experience IUGR.  There are multifactorial causes for growth restriction; some involve the other conditions mentioned here, such as a placental insufficiency, low amniotic fluid, or Twin-to-Twin Transfusion Syndrome (TTTS). If it is determined that a twin has completely stopped growing or is in distress, an early delivery may be the best option. 

Considered Term at 37 or 38 Weeks

Time to deliver twins
Optimal time to deliver twins may be earlier.. Erikona /E+ / Getty Images

Opinions differ on the optimal timing for delivery of twins or more. When preterm labor or other complications set in, the goal is often "the later the better." But in the last few weeks of pregnancy, different doctors may have different approaches. For some, an elective birth at 37 or 38 weeks is ideal for an otherwise uncomplicated twin pregnancy, so your doctor may schedule a delivery a couple of weeks early. Others prefer to wait and see. 


Dodd, J.M., et al., “Elective birth at 37 weeks of gestation versus standard care for women with an uncomplicated twin pregnancy at term: the Twins Timing of Birth Randomised Trial.” British Journal of Obstetrics and Gynecology, June 2012. pg. 964.

Habli, M., et al. “Twin-to-twin transfusion syndrome: a comprehensive update.” Clinicals in Perinatology, June, 2009. pg. 391.

Leeman, L. and Fontaine, P., “Hypertensive Disorders of Pregnancy.” American Family Physician, July 2008, pg. 93.

Moh, W., et al., “Extrinsic Factors Influencing Fetal Deformations and Intrauterine Growth Restriction.: Journal of Pregnancy, June 2012.

“Multiple Pregnancy.” American College of Obstetricians and Gynecologists, Accessed February 27, 2016. http://www.acog.org/Patients/FAQs/Multiple-Pregnancy

Saliva, H.M., et al., “Perinatal mortality associated with abruptio placenta in singletons and multiples.” American Journal of Obstetrics and Gynecology, July 2005, pg. 198.

“Twin Pregnancy Complications.” UCSF Fetal Treatment Center. Accessed February 27, 2016. https://web.archive.org/web/20111221205053/http://fetus.ucsfmedicalcenter.org/twin/

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