Twin Pregnancy Preterm Labor

Preterm Delivery (before 37 w) is the most common complication of a twin pregnancy. The average twin pregnancy delivers at about 35 weeks   Women who have had a previous preterm single baby appear to be at higher risk for preterm delivery than other women with a twin pregnancy [1,2].  In addition,  twin pregnancies conceived by assisted reproductive technology (in vitro)  may also be at increased risk for preterm delivery compared to women with naturally conceived twins [3-5]. Lastly women who deliver  twins at less than 34 weeks' have an increased risk of  preterm birth in future pregnancies [6].

Signs and Symptoms of Preterm Labor

  • Regular or frequent contractions (tightening of the uterus), equal to or greater than 6 times in an hour. Sometimes this feels like tightening of the belly.
  • Menstrual like cramps or abdominal cramps.
  • Low backache
  • Pelvic pressure
  • Increase or change in vaginal discharge (watery, mucus, or bloody)
  • Leakage of clear water or bleeding from the vagina
Call your doctor if you notice any of the above signs or symptoms. It is often  difficult to tell the difference between  true preterm labor and false labor . The diagnosis of preterm labor is usually made if there are regular contractions with effacement (thinning) of the cervix  to greater than or equal to  80%  and / or opening of the cervix to at least 2 centimeters.

What Causes Preterm Labor?

Spontaneous (unprovoked) preterm labor may result from several causes including infection, inflammation,  vascular disease (poor blood supply to the uterus and placenta) , an overstretched uterus, and abnormalities  of the cervix . The cause of many preterm births is never found [18]

Prevention of Preterm Labor

Bedrest,  intramuscular  and long term use of oral medications to stop contractions (tocolytics) are not recommended for the prevention of preterm labor in multiple pregnancies because these treatments are either ineffective and/or may cause harm.  Cervical cerclage (stitching the cervix closed) is also not recommended in multiple pregnancies except in specific circumstances  [7,12].

However, vaginal progesterone may be effective in  reducing bad outcomes in women with a twin pregnancy and a cervical length of 25 mm or less .  Cervical pessaries, small ring-shaped devices which are inserted around the cervix, may also be effective in reducing bad outcomes in women with a twin pregnancy and a cervical length of less than 38mm .

If there is enough time the babies can be given a medication (corticosteroid) to help the lungs mature and reduce other complications of being born prematurely.  A shortened cervix is a strong predictor of preterm delivery in twin pregnancies . The graph above shows how the risk of preterm delivery begins to increase rapidly as the cervix shortens to less than 25 mm.

Some health care providers use the cervical length and the fetal fibronectin test to select twin pregnancies at high risk for preterm delivery  for treatment with  corticosteroids before the mothers have gone into preterm labor. Other groups are studying the use of a cerclage pessary, a small ring-shaped device which is inserted around the cervix, to prevent preterm  births in twin pregnancy.

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