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Process of Labor for Full-Term and Preterm Birth Differs, New Research Finds

person in labor

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Key Takeaways

  • New research found that the process of preterm labor is different from full-term labor.
  • It comes down to differences in gene expression in the outer layer of the uterus.
  • Researchers believe this offers a possible answer to why treatments to delay preterm labor often don't work.

Every year, an estimated 15 million babies are born preterm (meaning they’re born before 37 weeks of gestation), per the World Health Organization (WHO). Preterm birth is sometimes caused by infection or a chronic condition like diabetes or high blood pressure, but often it’s not possible to pinpoint a reason. 

Research into preterm birth is crucial to improve understanding of why some people go into labor early and to develop solutions to help pregnant individuals carry their babies for as long as possible. 

A recent study, published in the American Journal of Obstetrics and Gynecology, found that the process of labor in full-term births is different from preterm births. It comes down to a difference in gene expression in the myometrium of people who gave birth preterm. 

The myometrium is the muscular outer layer of the uterus, designed to house and nourish the fertilized egg until the baby is ready to be delivered. The onset of full-term labor involves changes in gene expression that take the uterus from a relaxed to a contracting state. Let's take a deeper look at what the research showed.

About the Research 

The research team asked women who were having a cesarean section for permission to take a small sample of the muscle of the uterus during the operation. In total, muscle samples were obtained from seven different groups of women.

The first two groups had women at full-term who were in labor and those who were not yet in labor. The next four groups involved women in labor with preterm singletons or preterm twins and women not yet in labor with preterm singletons or preterm twins. The last group contained women experiencing preterm labor with chorioamnionitis, a bacterial infection of the uterus involved in some preterm births.

Danielle Jones, MD

Sometimes people labor and progress really quickly. Those preterm labors are more difficult to stop. Others have mild contractions and slow cervical change, which tends to respond better to intervention.

— Danielle Jones, MD

After extracting RNA—a nucleic acid that plays an important role in regulating cellular processes—from the samples, the researchers analyzed the expression of 44 candidate genes that are understood to play a role in the human labor process.

They discovered that the preterm myometrium gene expression was different from the full-term labor and full-term not-in-labor groups. This change was irrespective of whether the preterm group was in labor or not, whether they were single or twin births, and whether they were suffering from chorioamnionitis.

The results suggest there may be different myometrial pathways responsible for preterm labor, say the researchers. New treatments will need to not only relax the muscles of the uterus but also treat the cervix and the membranes around the baby, they add.

Signs and Causes of Preterm Labor

The presentation of preterm labor can range from mild abdominal cramps or back pain to the standard contractions you expect with labor, says Danielle Jones, MD, a board-certified OBGYN. Other signs and symptoms to watch for include increased or new/different vaginal discharge, leaking fluid, pelvic pressure, dull backache, regular abdominal tightening, or your water breaking.

Often, no cause is identified for preterm labor. “Sometimes, it can be caused by vaginal or urinary tract infections, multiple gestations like twins or higher-order multiples, or prior cervical procedures,” says Dr. Jones. “But sometimes it’s just something that happens.”

Identifiable risk factors include a history of preterm birth in other pregnancies, a shortened cervix, smoking or drug use during pregnancy, and low pre-pregnancy weight. “Preterm labor also seems to be more common in teens and those who are over 35 years old,” Dr. Jones adds. 

Delaying Preterm Labor

If you think you might be in preterm labor, the most important thing to do is seek medical care. “This is especially important if you have been planning for a home delivery, as preterm labor and birth is a contraindication to delivering a baby at home and is an obstetrical emergency,” says pediatrician, neonatologist, and Aeroflow Breastpumps medical director Jessica Madden, MD, who cares for many preterm babies. 

People who are pregnant and go into labor preterm are usually admitted to a hospital’s obstetrics ward and monitored closely. "In most cases, women go onto immediate bed rest and receive a series of two corticosteroid injections, which are very important as they help the baby's lungs develop so that they have less of a risk of lung and breathing problems if they are born prematurely," says Dr. Madden. 

Magnesium is also given to pregnant parents who present in preterm labor below about 32 weeks gestation. It helps to improve premature babies’ neurodevelopmental outcomes, she adds. Other options for treating preterm labor include medications like Indocin, Nifedipine, and sometimes antibiotics.

Danielle Jones, MD

Our ability to use each medicine and its effectiveness is highly dependent on each individual and the cause of the preterm labor.

— Danielle Jones, MD

"Our ability to use each medicine and its effectiveness is highly dependent on each individual and the cause of the preterm labor," says Dr. Jones. "Sometimes people labor and progress really quickly. Those preterm labors are more difficult to stop. Others have mild contractions and slow cervical change, which tends to respond better to intervention."

The new research helps to narrow the search for potential treatments for preterm labor, reducing the risk of babies being born too early.

What This Means For You

If you think you might be at risk for preterm birth, share your concerns with a healthcare provider. There are some ways to reduce your risk of preterm labor, such as maintaining a healthy weight during pregnancy, receiving proper treatment for any chronic health problems, such as diabetes or thyroid issues, and reducing stress.

Research into preterm labor is ongoing and hopefully will lead to effective methods to help people achieve a full-term pregnancy.

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3 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. World Health Organization. Preterm birth. Updated February 19, 2018.

  2. Phung J, Wang C, Reeders J, et al. Preterm labor is a distinct process from term labor following computational analysis of human myometrium. Am J Obstet Gynecol. 2021. doi:10.1016/j.ajog.2021.07.002

  3. Mayo Clinic. Preterm labor. 2021.