For example, if the absolute risk of having a stillbirth at 41 weeks was 1. But some people may consider the actual or absolute risk to still be low—1. Please see our handout on Talking about Due Dates for Providers for tips on how providers can discuss the risk of stillbirth. The second important thing that you need to understand is that there are different ways of measuring stillbirth rates.
Depending on how the rate is calculated, you can end up with different rates. Up until the s, some researchers thought that the risk of stillbirth past weeks was similar to the risk of stillbirth earlier in pregnancy. So, they did not think there was any increase in risk with going past your due date. However, in , a researcher named Dr.
Yudkin published a paper introducing a new way to measure stillbirth rates. Yudkin said that earlier researchers used the wrong math when they calculated stillbirth rates—they used the wrong denominator! Yudkin, Wood et al. Instead, we need to know how many stillbirths happen at 41 weeks compared to all pregnancies and births at 41 weeks. In other words, you have to include the healthy, living babies that have not been born yet in your denominator. When researchers began using this new formula to figure out stillbirth rates, they found something very surprising—the risk of stillbirth decreased throughout pregnancy, until it reached a low point at weeks, after which the risk started to rise again.
This finding—that the risk of stillbirth decreases throughout pregnancy, and then increases sometime after weeks—has been found many times by different researchers in different countries. In other words, there are higher rates of stillbirth earlier in pregnancy, then they go down until around weeks, after which they rise again. Because the risk of stillbirth starts to go up even more at 40, 41, and 42 weeks, some researchers argue that although 40 weeks and days may be the physiological length of pregnancy, 40 weeks may be the functional length of a pregnancy.
And although the stillbirth rates may seem low overall, if you happen to be a parent who experiences the 1 in event at 42 weeks Muglu et al.
Even after researchers began using the new way of calculating stillbirth rates, there was still controversy about the best way to calculate this new formula for measuring stillbirth rates. Other researchers argued that most people and doctors! Hilder et al. They just want to know what the risk would be if they waited one more week until the next appointment, or even a few days.
Boulvain et al. In the end, you will find that stillbirth rates vary from study to study, depending on whether the researchers report the actual stillbirth rate, or the open-ended stillbirth rate. Some of the researchers used open-ended stillbirth rates, and some of them used actual stillbirth rates. All of the researchers found a relative increase in the risk of stillbirth as pregnancy advanced. To get an accurate picture of stillbirth in people who go past their due date, it would be best to look at studies that took place in more recent times.
To see all of the other studies, click to view the entire table here. All 3 of these studies used the actual stillbirth rate—not the open-ended stillbirth rate. Two studies used ultrasound to calculate gestational age, and one study used the LMP. The largest meta-analysis to date on risks of stillbirth and newborn death at each week of term pregnancies was published in Muglu et al. The researchers included 13 studies 15 million pregnancies, nearly 18, stillbirths.
The risk of stillbirth per 1, was 0. Based on their data, Muglu et al. To experience one additional stillbirth, there would need to be at least 2, people waiting for labor for one more week starting at 39 weeks. At 40 weeks, 1, people would have to wait for labor for one more week to experience one additional stillbirth.
At 41 and 42 weeks, only and people, respectively, would have to wait for labor for one more week to experience one additional stillbirth. The researchers also found evidence that health care systems are failing Black mothers and babies—an alarming but common theme in health care research. Black mothers were 1. When they looked only at low-risk pregnancies, the risk of stillbirth was 0. Low-risk pregnancy was defined as pregnancies with a single baby, no congenital abnormalities, and no medical conditions in the mother.
There was no additional risk of newborn death when giving birth between 38 and 41 weeks, but the risk of newborn death did increase beyond 41 weeks.
Other factors that do not necessarily cause stillbirth but may increase the risk of stillbirth, in general, include:. Of course, parents can still experience the stillbirth of a child even when none of these risk factors are present. To read more about theories of unexplained stillbirth, read this article here.
However, up until recently, there was no research on this topic. In , researchers published the first study looking at biological markers of aging in placentas. In this study, researchers in Australia collected placentas from 34 people who gave birth between weeks of pregnancy, 28 people who gave birth between weeks, and 4 people who experienced stillbirths between 32 and 41 weeks Maiti et al.
Five or more tissue samples were removed from each placenta, and the samples were analyzed using a variety of biochemical tests. Overall, the analysis of the placentas from the week pregnancies and from the stillbirths showed increased signs of aging, with decreased ability to transport nutrients to the baby and waste products away from the baby, compared to the placentas from the earlier term births.
The rate of placental aging varied in different pregnancies, and the authors stated that not all of the week placentas showed signs of aging. We reached out to the authors to find out more, and they told us that one-third of the week placentas showed increased signs of aging compared to the week placentas.
This means that two-thirds of the week placentas did not show signs of aging. You can watch a minute video describing the findings of this emerging research here. I would also like to thank my expert reviewers for an earlier version of this article—Shannon J. Join others who also want to help bring evidence-based care to their local community. Rebecca Dekker Don't miss an episode!
Don't miss an episode! Subscribe to our podcast: iTunes Stitcher On today's podcast, we're going to talk with Ihotu Ali, MPH, who is writing about research on the effects of racism on pregnancy and birth outcomes. Rebecca Dekker. PhD, RN. Get our one-page handout on Inducing for Due Dates to use in your informed decision making! Early term babies are born between 37 weeks 0 days and 38 weeks 6 days Full term babies are born between 39 weeks 0 days and 40 weeks 6 days.
Late term babies are born between 41 weeks 0 days and 41 weeks 6 days Post term babies are born at 42 weeks and 0 days or later. How do you figure out your estimated due date? What is the most accurate way to tell how far along you are? Why is LMP less accurate than using ultrasound? LMP is less accurate because it can have these problems: People can have irregular menstrual cycles, or cycles that are not 28 days People may be uncertain about the date of their LMP Many people do not ovulate on the 14 th day of their cycle The embryo may take longer to implant in the uterus for some people Research indicates that some people are more likely to recall a date that includes the number 5, or even numbers, so they may inaccurately recall that the first day of their LMP has one of these numbers in it.
What is the best time to have an ultrasound to determine gestational age? The most likely birthdate is seven days early, according to a huge sample of birth information put together for the Globe by Brookings Institute researcher and WhenToExpect.
First children tend to stay put for a little longer. On average, they show up two or three days early. Second and third children arrive five to six days early. Boys and girls arrive at roughly the same time. The older you are, the more likely you are to give birth early. Teenage moms tend to give birth about three days early, while moms in their 40s trek to the hospital about a week in advance.
Reviewed by: Armando Fuentes, MD. Larger text size Large text size Regular text size. Here's what you can do to have a healthy pregnancy. During pregnancy, help your baby grow strong and healthy. Be sure to: Start prenatal care as soon as you think you're pregnant.
Prenatal care is the health care that you get during pregnancy. All pregnant women should see a health care professional as soon as they think they're pregnant, and should plan regular prenatal visits throughout pregnancy. Get health problems treated. It's best to have any health problems like diabetes , depression, or high blood pressure under control before becoming pregnant.
But if you don't, talk to your doctor right away about a treatment plan. Eat a healthy diet. It's important to eat a variety of healthy foods before and during pregnancy. Medical Myths Health.
The truth about three childbirth myths. Share using Email. By Claudia Hammond 27th November Some myths about babies and what brings on labour have proved remarkably persistent. BBC Future put them under the microscope. A large study found that three-quarters of women whose waters had broken went into labour within 24 hours.
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