Inducing labor at 39 weeks reduces the need for some C-sections

It's just one of the reasons why some doctors are encouraging slightly shorter pregnancies.
Mother with short pink hair kissing newborn in hospital after induced labor at 39 weeks
Just shaving one week off a pregnancy could make a big difference for mother and baby. DepositPhotos

In 2020, about 20,000 infants died before reaching their first birthday in the US. And while there are a number of contributing factors, one of the leading causes of death, complications during pregnancy, may be somewhat preventable if the baby is delivered sooner. 

At first glance, 40 weeks seems to be the sweet spot for giving birth to a healthy child. The risk for health complications skyrockets if newborns arrive before their due date. Going past the 40-week due date might also put the baby and mother in harm’s way as there’s an increased chance for stillbirth, lower amniotic fluid which could restrict oxygen delivery to the fetus, and postpartum hemorrhaging. 

Yet more doctors are now advising their patients to induce labor one week earlier. A growing body of research and clinical trials, including one published on July 20 in the journal PLOS Medicine, are showing that inducing labor at 39 weeks is safe for both the mother and child and is a time when there’s the least amount of complications. Still, it’s not a one-size-fits-all approach and depends on a person’s medical history and well-being of the fetus. Some conditions include if they are carrying only one fetus, if there was no previously spotted complication or condition in mother or fetus, and if it’s their first pregnancy.  

The fetus is ‘fully developed’ at 39 weeks.

The last weeks of pregnancy are the most important in the organ development for a fetus. By 39 weeks, the lungs and brain are fully developed and the baby is already shifting to a downward position. “At [that time], pulmonary maturity is pretty certain. Inducing too early, you could have a 2 to 3 percent chance of the lungs not being ready,” says G. Thomas Ruiz, an OB/GYN at MemorialCare Orange Coast Medical Center in California. Even if babies born at 36 to 38 weeks had fully matured lungs, they are still at a two-fold increase for sepsis and lung-related mortality.

It reduces the need for C-sections.

In some areas of the world, the risk of dying from a cesarean birth, or a C-section, is less than one in 12,000 (compared to the 1 in 10,000 deaths from vaginal births). But while the mortality rate is low, it is still a major abdominal surgery and comes with a number of health complications. Individuals who go through the procedure take longer to recover after birth, deal with more pain from being opened up, and have a higher chance for post-op infection.

[Related: C-section babies have a unique microbiome—here’s why that matters]

Inducing labor at 39 weeks helps decrease the need for the surgery during a person’s first pregnancy. In 2018, researchers in the US released the results of a massive clinical trial called ARRIVE that investigated the safety and benefits of giving birth a week earlier. Of the 3,062 women induced at 39 weeks, 18.2 percent had a lower rate of C-sections than the 22.2 percent of women who were supervised for any pain or issues at 39 weeks. If the procedure was needed, they did not require as big of an incision during surgery. Ultimately, the authors estimated one C-section delivery can be avoided for every 28 pregnancies that are induced at 39 weeks. What’s more, women who shortened their pregnancy to 39 weeks showed a lower risk of complications like seizure, perinatal death, and respiratory support during and after labor than those who began labor at 40 weeks.

Inducing labor could address some health inequities in maternal care.

One benefit to shortening pregnancy is potentially offsetting inequities in maternal care and other health resources for people living in low-income communities. The new PLOS Medicine paper found that across 500,000 women with low-risk pregnancies in the U.K., 9.5 percent were induced into labor at 39 weeks. Many of those individuals were less likely to experience birth complications such as stillbirths and neonatal deaths.

Babies born at 39 weeks versus 40 weeks showed a small reduction in health problems following delivery. There was 3.3 percent of complications in infants born at 40 weeks compared to the 3.3 percent observed in those born at 39 weeks. This decrease in risk was most apparent among women living in low socioeconomic areas.

The benefits of induction were observed mainly in residents of socioeconomically deprived areas and in those who have never given birth before, explains Ipek Gurol-Urganci, an associate professor at London School of Hygiene and Tropical Medicine and senior study author. “We’re suggesting that these women are offered induction of labor at this stage.”

Pregnant people from low-income households might have limited access to educational and health resources than people of a higher class. Gurl-Urganci says this socioeconomic deprivation, which disproportionately affects individuals with minority ethnic backgrounds, is linked to higher rates of maternal smoking, obesity, and mental illness. Poor housing conditions may also affect pregnancy outcomes because mothers are more likely to be exposed to air pollution, feel socially isolated from others, have poor access to maternity care, and experience chronic stress because of “economic strain, insecure employment, and more frequently stressful life events,” she adds.

Who should get induced at 39 weeks?

The latest research replaces the previous idea that giving birth before 40 weeks is always harmful—but Gurl-Urganci emphasizes that this doesn’t mean that everyone should go into labor early. Rather, it’s a potential option for people with low-risk pregnancies living in risky conditions. “The pros and cons should be explained to each woman, taking into consideration her individual circumstances. We should then support her in whatever decision she feels is right for her,” Gurl-Urganci adds.

[Related: We don’t really know how many pregnant people are dying in the US]

Despite the recommendation that labor only be induced in people going through their first pregnancy, there might be exceptions, Ruiz says. “For a woman who has had at least one vaginal birth, their cervix will often be favorable at 39 weeks. We still prefer to let them go into spontaneous labor, but their success rate for elective induction to vaginal delivery is very high, [and] they rarely end up with a C-section delivery.” One factor to consider is whether someone is physically ready for labor, including if their cervix is dilated and the baby’s head is facing fully downwards. Otherwise, waiting another week might be the best decision for both mother and child.