What Are the Signs of Preterm Labor?
By Shailen Shah, MD
Lead Physician and Medical Director—Virtua Maternal-Fetal Medicine
Director—Virtua Maternal-Risk Program
Preterm labor occurs when an expectant mom’s body prepares to give birth before the 37th week of pregnancy. This can lead to premature birth, which increases the baby’s risk of health problems.
Because preterm labor occurs in about 10 percent of pregnancies and sometimes has no apparent cause, it’s a legitimate concern if you're expecting—even if you aren’t high risk for preterm labor. However, you and your doctor can work as a team to identify any risk factors, spot the warning signs of preterm labor and, if necessary, take action to prevent complications.
Identifying preterm labor risk
When it comes to preterm labor, the motto is “treat when you must, but prevent when you can.” Prevention starts with identifying risk factors early in your pregnancy.
If you're pregnant with more than one baby or have had preterm labor in a previous pregnancy, you're at an increased risk of preterm labor. However, studies have shown that women who have a short cervix (the lowest part of the uterus that opens into the vagina) also are at an increased risk of preterm labor. That’s because a short cervix is more likely to open before the baby is fully developed.
To determine if you have a short cervix, your doctor may take a cervical length measurement during the routine ultrasound scan that’s performed around the 20th week of pregnancy. If your doctor sees that you have a short cervix, he or she will continue to measure your cervix and may prescribe medication to prevent preterm birth.
Preventing preterm labor
If you’re at an increased risk for preterm labor, your doctor may prescribe a hormone called progesterone to help prevent contractions. It’s given daily vaginally or weekly as a shot and is usually only used if you're expecting one baby, not multiples.
Cervical cerclage, or a cervical stitch, is another procedure that helps prevent preterm birth. An OB/GYN uses a stitch to close the cervix, which helps prevent it from opening too early. The stitch then is removed around 37 weeks of pregnancy.
Understanding the signs
During pregnancy, your body goes through many changes. Part of your doctor’s job is to help you learn to pay attention to physical changes and interpret what’s normal and what’s not—whether it’s your first pregnancy or fourth. Even if you’re not considered at high risk for preterm labor, you should notify your doctor right away if you experience any symptoms or changes that may signal preterm labor, including the following:
- Contractions that occur more than four times per hour for more than an hour
- Contractions that wake you up or prevent you from sleeping
- Cramping in your lower abdomen
- Dull backache below the waistline
- Increased or intense pelvic pressure
- Vaginal bleeding
- Watery vaginal discharge or changes in vaginal discharge
If you’re showing signs of preterm labor, your doctor may test your vaginal discharge for the presence of fetal fibronectin, which is a glue-like substance that’s found in the uterus. Fetal fibronectin is normally detected in vaginal discharge near the end of pregnancy. If your fetal fibronectin test is positive, you’re at increased risk of going into preterm labor.
If your doctor thinks that you'll go into preterm labor—or if preterm labor has already started—he or she can take action to help keep you and your baby as healthy as possible. Depending on your specific circumstances, your doctor may recommend restricted activity or advise you to avoid exercise, sexual intercourse, or travel.
Your doctor also may recommend giving you steroid injections to help speed up the development of your baby’s lungs. These injections can help give your baby a better chance of survival in case he or she is born prematurely. However, to have the optimal effect, steroid injections need to be given at least 48 hours before your baby is born. Your doctor also may prescribe intravenous or oral medications to stop contractions.
Although there are a variety of medical advances that can identify your preterm labor risk and help prevent preterm delivery, learning to “read” your body is one of the most important things you can do to keep you and your baby safe.
For more information about high-risk pregnancy care at Virtua, call 888-847-8823.
Updated January 14, 2022