Change in Cervical Length Predicts Preterm Labor in Twin Pregnancy

A new study published in a recent issue of Twin Research and Human Genetics found that a change in cervical length (CL) over time is a strong predictor of spontaneous preterm delivery (SPTD) for women expecting twins. (You can read the abstract here.) Doctors from Seoul National University College of Medicine followed 190 women, all pregnant with twins, all with “normal” cervical lengths (25 mm or longer) at mid-trimester (Week 20 to 24), and all asymptomatic (translation: all were enjoying a healthy pregnancy with intact amniotic membranes and free from problems such as fetal anomalies, twin-to-twin transfusion syndrome, maternal complications or uterine contractions). The moms-to-be had an initial CL measurement taken during routine ultrasound examination around Week 20 to 24, and then a follow-up CL measurement four to five weeks later.

The results? When a woman’s CL shortened 13 percent or more four to five weeks after her initial measurement, she had a significantly greater chance for preterm delivery before Week 32 to 34.

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Although cervical length has always been an effective tool for predicting preterm labor (researchers have know that women have a much greater chance of a preterm birth by Week 32 to 34 when a cervix measures 20 mm or less at Week 20 to 24), there’s never been a study that looked at the chance of SPTD in women with a “normal” cervical length of 25 mm or greater mid-trimester. This study suggests that even if a mom-to-be expecting twins is enjoying a symptom-free pregnancy and has a normal CL length at mid-trimester, a follow-up measurement should be taken four to five weeks later to reassess her risk. Even if a woman expecting twins shows no signs of complications, it would be prudent to watch for a change in cervical length.

As the test is non-invasive, it’s a great tool for the fight against preterm delivery. So if you’re pregnant with twins, speak to your doctor.