Staying pregnant to full term, or 39-40 weeks, is one of the best ways to give babies the time they need to grow. Preterm birth—or delivery before 37 weeks of pregnancy—can prevent growth and development from happening inside a baby's body during the final weeks of pregnancy.1,2

Read on to learn about preterm birth, risk factors for preterm birth, and the important growth and development that occurs inside the womb.
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What is Preterm Birth?

Preterm birth is the delivery of a baby less than 37 weeks of pregnancy.2 The last weeks of pregnancy are critical to a baby's growth and development. Click below to understand the definitions week by week.

Preterm is a birth of an infant before 37 weeks of gestation

Preterm birth is more common than you may think. In the United States, approximately 400,000 babies are born too early—or preterm—each year.6 More than 70% of all preterm births in the United States are late preterm births, a time in which important developments are still happening.7

Approximately 1 in 10 babies in the United States is born premature6

Babies Continue Important Development,
Even in those Final Weeks of Pregnancy

Explore inside the womb through this interactive 360° video, and discover the growth you can’t see and what a baby has to gain by reaching full term.

Important developments occur during the last weeks of pregnancy. Babies need every week inside the womb, as the brain, lungs, and liver are among the last organs to develop. Regardless of birth weight, babies born early are also more likely to be re-hospitalized.8 That's why getting to full term is important.

Around week 35, the brain is only 2/3 the size of a full term baby's.8
Hearing is not fully developed until full term.9
A baby's liver is not mature enough to prevent jaundice until full term.8,10
A baby may not have enough body fat to keep temperature steady until week 37.8,10
Breathing, sucking and swallowing reflexes are not ready until 34 weeks or later. A preterm birth may cause feeding and nutrition problems.8,10
Lungs continue to develop until the end of pregnancy, and babies may have trouble breathing if born early.8

Compared to term infants, late preterm infants were:8

Compared to term infants, late preterm infants are 4 times more likely to have at least 1 medical condition diagnosed

more likely

to have at least 1 medical condition diagnosed
Compared to term infants, late preterm infants are 3.5 times more likely to have 2 or more medical conditions diagnosed

more likely

to have ≥2 conditions diagnosed
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Risk Factors

It's important to know and understand the risk factors for preterm birth. Preterm birth is often unexpected. Some women may have an early delivery due to a medical situation, and sometimes one may have a greater chance of preterm birth due to known risk factors.1,2

Leading Risk Factors

  • Prior preterm birth (unexpectedly delivered a baby before 37 weeks in the past)
  • Pregnant with twins, triplets, or other multiples
  • Problems with uterus or cervix
  • African-American heritage

Other Risk Factors

  • High blood pressure, stress, diabetes, or being overweight or underweight
  • Smoking, drinking alcohol, or using drugs
  • Short time between pregnancies
  • Certain infections during pregnancy

Are You At Risk?

If you think you may be at risk for preterm birth, seek early prenatal care. Bring the risk factors checklist to your healthcare provider and talk with him or her about ways you can reduce your risk, including possible treatment options.

Signs & Symptoms of
Preterm Labor

Pregnant women should be familiar with the signs of preterm labor.12 If any signs or symptoms of preterm labor occur before a baby's due date, contact a healthcare provider as soon as possible.

Contractions, or tightening of the belly muscles, every ten minutes or less

Belly cramps with or without diarrhea

Low, dull backache

Cramps resembling menstrual cramps

Feeling of pressure in the pelvic area

A change in vaginal discharge

A Message from Moms to Moms

Hear how other moms learned about their preterm risk through these stories and video.

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“I was stunned to learn that delivering prematurely put me at an even higher risk for another preterm birth. Understanding your risk for preterm birth is important to a healthy pregnancy."
- Teletia, Preemie mom
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"I've had two preterm births, and from my experience, I encourage expecting moms to talk with their doctor or nurse, especially if they think something is wrong during their pregnancy. The doctor or nurse will help them determine if there is an issue and how to help them have the best chance for a full term pregnancy."
- Julieta, Preemie mom

Learn More About Preterm Birth: Free Educational Resources

If you’re a healthcare provider, patient advocacy organization, insurance company, or someone interested in sharing educational materials, you can order free The Growth You Can’t See materials to help bring the importance of the last six weeks to life. Materials for order include a postcard to share with your patients to go inside the womb for a virtual reality experience, as well as an educational brochure and poster. You can also download a free digital toolkit of all the materials offered in the resource center below. Some materials are available in multiple languages.

Preterm Birth Resource Center

In the Womb: An Interactive 360º Video Experience

Explore the important development milestones during the last weeks of pregnancy with this interactive video.

In the Womb: Video Postcard

This postcard provides helpful information on how to view the interactive video, In The Womb: From Head to Toe.

Are You At Risk For Preterm Birth? Checklist

Bring this checklist with you to your next doctor appointment to learn if you may be at risk for preterm birth.

Brochure: Delivering the Facts on Preterm Birth

Read this brochure for an overview of the basics of preterm birth. It is available for download in multiple languages including Spanish, Vietnamese, Russian, Chinese, Tagalog, Arabic, and Korean.

Development Milestones Poster

View important development milestones that occur during the last few weeks of pregnancy. It is also available in Spanish.

Preterm Birth 101 Video

Featuring Dr. Judette Louis, a Maternal-Fetal Medicine specialist, this video helps you learn about whether you may be at risk of delivering preterm. At the time of video filming, Dr. Louis was a consultant of AMAG Pharmaceuticals, Inc.

Health & Family Segment

Hear from a Maternal-Fetal Medicine specialist on preterm birth and its risk factors, and from a mom of two premature babies who also shares her experiences. At the time of video filming, Dr. Biggio was a consultant of AMAG Pharmaceuticals, Inc.

40 Weeks Webisode Video

Hear a mom discuss her pregnancy story and share her experience of how she learned she was at risk for delivering preterm. The video was sponsored by AMAG Pharmaceuticals, Inc. as part of their sponsorship of 40 Weeks.

  • In the Womb: Video Postcard

  • Postcard
  • Brochure: Delivering the Facts on Preterm Birth

  • Brochure
  • Development Milestones Poster

  • Poster
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