Research Shows You Should Aim for a Full-Term Pregnancy

A full-term pregnancy is a pregnancy that lasts from 39 to 40 weeks. Each week of gestation is crucial for your baby's health and development. Moreover, conclusive research shows that birthing a baby before 39 weeks (and at or after 41 weeks) puts them at higher risk for a range of health and developmental problems.

"The evidence is so compelling that a growing number of American hospitals are launching programs to help prevent elective deliveries before 39 weeks of gestation," says Diane Ashton, MD, MPH, deputy medical director of the March of Dimes.

Here's everything you need to know about full-term pregnancies, from how many weeks a full-time pregnancy is, and why it matters.

What Is a Full-Term Pregnancy?

While many people believe a full-term pregnancy lasts 37 weeks, that's not actually the case. According to the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine, a full-term pregnancy spans between 39 weeks, 0 days, and 40 weeks, 6 days.

During a full-term pregnancy the parent gives birth somewhere between one week before their due date and/or up to one week afterward. Babies born during weeks 37 and 38 are considered early-term, those born during week 41 are late-term, and those delivered at 42 weeks or later are post-term. Note that delivering after full term also has added risks for both the baby and the pregnant person.

These distinctions are important because babies tend to do best when born during weeks 39 and 40, with babies born before 39 weeks having a higher risk of breathing problems, developing infections, and spending time in the NICU. Additionally, babies born after 41 weeks have a higher incidence of complications as well.

Full-Term Pregnancy: Then vs. Now

In the past, any time between week 37 to week 42 pregnancies were considered at term, and babies ready for delivery. Most physicians believed that major organ development was complete at this time, and babies simply packed on pounds during the last stretch of pregnancy.

Doctors and hospitals routinely scheduled elective inductions and C-sections for pregnant parents who were only 37 and 38 weeks pregnant. The appeal of this approach was that you could control when you're giving birth, allowing you to make sure your loved ones—and your own doctor—could be at your delivery.

However, research has established a clear connection between early-term deliveries and an increase in the number of babies in the neonatal intensive care unit (NICU), establishing just how important those last few weeks are.

"We now know that important organs, such as the lungs and the brain, are not fully developed until 39 weeks," says Jason K. Baxter, MD, an OB-GYN who specializes in high-risk pregnancies at Thomas Jefferson University Hospital, in Philadelphia.

Issues in Birth Planning

There are many challenges parents face when trying to plan their birth to achieve a full-term pregnancy. Due dates are often miscalculated, especially by ultrasound and for those with irregular periods. Potential discrepancies can result in doctors delivering premature babies who have not reached 37 weeks of development. These babies are even more likely to have complications and end up spending time in the NICU, causing stress for families, and potentially, lifelong health issues for their babies.

Moreover, some early-term inductions don't work because the pregnant person's body is not ready to go into labor. Studies show that approximately 20% of inductions are not successful. These individuals are more likely to end up with C-sections that they may not have needed if they had waited for labor to start on its own. If you're curious what your due-date might be, check out our calculator below.

Why Those Last Few Weeks Matter

Many early-term babies will end up healthy, but others experience complications that are far less common for those born closer to 40 weeks. And according to the March of Dimes, waiting until 39 weeks of gestation can help ensure full development of the brain, lungs, and liver.

Research has found that there are several risks associated with delivering before a full-term pregnancy. Here are some of the most common challenges.

• Difficulty breathing: Research shows that babies born by C-section before 39 weeks have more breathing difficulties and other complications than babies delivered by C-section after 39 weeks.
• Increased NICU odds: Babies delivered electively at 37 weeks are significantly more likely to end up in the NICU or have serious respiratory troubles than babies born at 39 weeks or later. Babies who arrive at 38 weeks are also more likely to have complications.
• Lack of surfactant: The compound surfactant enables babies to breathe independently, continues to be produced in greater amounts during the last month of pregnancy and decreases your baby's risk of developing breathing problems once they're born.
• Underdeveloped skin: Your baby's skin thickens during the last few weeks of pregnancy, and they're accumulating more body fat, which will help them maintain their own body temperature after they're born.
• Underdeveloped brain and organs: Their organs—including the liver, brain, and lungs—are still undergoing crucial development as well. Important brain and nerve connections are also being made to help the baby suck, swallow, breathe, and even sleep better once they're born.

This doesn’t mean that babies born before 39 weeks will have health problems; many babies born before full-term, particularly at 37 or 38 weeks, are perfectly fine—but health outcomes statistically are generally better once babies hit that 39-week gestation mark.

When To Talk to Your Doctor

If you’re concerned about your ability to go full-term for your pregnancy, or if you're worried about having an early-term baby, talk with your OB-GYN or midwife. they will be able to go over all of the health risks and things to watch out for if your baby is born early, and what will happen if you give birth pre-term.

Your doctor knows you, your medical history, and what’s been going on with your pregnancy, and they'll be able to provide you with personalized advice and guidance to help ease your worries and plan for a healthy birth.

That said, it's important to note that if you do go into labor early, your baby can still be healthy. Doctors and hospital staff are well-equipped to care for you and your baby, should the need arise. So, while you should aim to carry your baby as long as possible, many facilities can (and do) care for babies born at or before 37 weeks with excellent results.