Preterm history at a glance

Preterm birth is when a baby is born before 37 weeks gestation (birth prior to 39 weeks, but after 37 weeks, is considered near-term). Preterm birth is fairly common, affecting about 1 in 10 infants born in the United States.

Preterm birth can be dangerous because the last few weeks of pregnancy are important for a baby’s development. It’s during the final weeks of pregnancy that organs like the lungs, liver, and brain fully develop.

What are the risk factors?

There are several risk factors that contribute to a woman’s likelihood of delivering preterm. Some factors are manageable, like smoking. Many factors are unavoidable, like having a short cervix or hereditary gum disease. Often, the reason for preterm labor is unclear. Below are more risk factors:

  • History of preterm birth
  • Smoking
  • Overweight (High BMI)
  • Underweight (Low BMI)
  • Short cervix
  • Anemia
  • Gum disease
  • Untreated UTI
  • Vaginal infection

What are the signs and symptoms?

The symptoms of preterm birth are similar to those of any person going into labor. When going into preterm labor, people experience contractions every ten minutes or less and a combination of the below symptoms:

  • Intense lower backaches
  • Pelvic pressure
  • Vaginal bleeding

Others may experience an increase in discharge, diarrhea, and abdominal cramping.

Can I reduce risk?

Studies show that weekly progesterone treatments may help reduce the risk of preterm birth for those who have certain risk factors, like a short cervix.

For those with a history of preterm birth, some research suggested that progesterone treatment was helpful, and that getting weekly progesterone injections would lower the risk of preterm labor. However, the PROLONG study published in 2020 found that weekly progesterone injections did not have a significant benefit for those with a history of preterm birth. Because the evidence is mixed, if you have a history of preterm birth, talk through the possible benefits and risks of progesterone treatment with your healthcare provider.

Cervical cerclage is another tool used to help prevent preterm birth, but is notably less effective than progesterone.

The bottom line

Preterm birth is a major concern for many parents and physicians, so it’s important to know what to look for, especially if you’ve delivered preterm in the past.

Reviewed by the Ovia Health Clinical Team


  • “Preterm (Premature) Labor and Birth.” American College of Obstetricians and Gynecologists. American College of Obstetricians and Gynecologists, November 2016. Retrieved December 1 2017.
  • “Preterm labor.” Mayo Clinic. Mayo Clinic, October 19 2016. Retrieved December 1 2017.
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