Another mark against "nine months": A vast majority of twins and other multiples are born in the seventh or eighth month of pregnancy. The researchers discovered that the median pregnancy was not days, but days — and that was after excluding pre-term or post-term babies and accounting for a woman's weight, alcohol use, sex during pregnancy, and other factors.
This means a "typical" pregnancy likely lasts 38 weeks and 2 days — or 8 months, 24 days, and 16 hours. Note: If you're counting from the last menstrual period, which is a very imprecise way to measure pregnancy duration, it's more like 40 weeks and 5 days. The NIH study's real kicker, however, is how much the length of a traditional pregnancy can vary: by a whopping 37 days, or 5 weeks , spanning before and after the day mark.
And if you aren't convinced this actuarial nitpicking matters, consider the fact that some doctors can and do rush pregnant women into cesarean sections because of timing concerns, and the procedure — while typically very safe — not only costs thousands of dollars more than a vaginal birth, but also increases many kinds of risks to babies and their moms. All of that said, the NIH researchers did not go so far as to make a clinical recommendation; after all, women is a small sample size.
Yet it stands to reason that freely passing around a nice, round, and imprecise number could have some real and unfortunate consequences.
For you. We support research, lead programs and provide education and advocacy so that every family can have the best possible start. Building on a successful year legacy, we support every pregnant person and every family. March of Dimes, a not-for-profit, section c 3. Privacy, Terms, and Notices , Cookie Settings. Register Sign In. Hi Your dashboard sign out.
Need help? Frequently asked questions Contact us. Baby Caring for your baby Feeding your baby. Ambassadors Ambassadors Celebrity Advocate Council. Mission stories Spotlights Impact Stories. What is full term? E-mail to a friend Please fill in all fields. Please enter a valid e-mail address. 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? Should a due date be changed based on a third trimester ultrasound? How long is a normal pregnancy? Is it really 40 weeks? Why is this method wrong? So how can we deal with this problem?
There have been two studies that measured the average length of pregnancy using survival analysis: Study finds that estimated due date is 3 to 5 days AFTER 40 weeks In a very important study published in , Smith looked at the length of pregnancy in 1, healthy women whose estimated due dates, as calculated by the first day of the last menstrual period, were perfect matches with estimated due dates from their first trimester ultrasound Smith, a.
Study finds that estimated due date should be closer to 40 weeks and 5 days In , Jukic et al. So what was the average length of a pregnancy in this study? Are there some things that can make your pregnancy longer? Other factors that may make your pregnancy more likely to go longer include: Higher body mass index before you get pregnant Halloran et al.
In , Caughey et al. The participants in this sample all gave birth at Kaiser Permanente hospitals in northern California. The overall use of interventions Cesareans and inductions in this sample was not listed. The participants in this study were mostly well-educated. The rate of inductions was not listed.
This was the same time period and same hospital as his study, but this time the researchers only looked at low-risk people who had health insurance. The overall Cesarean rate was The authors also took whether or not people had inductions into account when they calculated the risks of going past your due date Caughey et al.
Risks for mothers: The risk of chorioamnionitis infection of the membranes was lowest at 37 weeks 0. However, these numbers are much higher than are typically seen, and are partially related to the high use of vacuum and forceps in this study.
What about the risk of stillbirth? There are two very important things for you to understand when learning about stillbirth rates. First, there is a difference between absolute risk and relative risk. Absolute risk is the actual risk of something happening to you.
Relative risk is the risk of something happening to you in comparison to somebody else. How do you measure stillbirth rates? Actual stillbirth rates vs. So what is the risk of stillbirth as you go past your due date? What factors can increase the risk of stillbirth? Also, small for gestational age babies are often growth restricted at the week ultrasound. So, the gestational age for these babies is often under-estimated.
This means that babies who are small for gestational age may be more post-term than we realize they are—increasing their risk while also leaving us unaware of their true gestational age Morken et al. The traditional way of calculating the estimated due date 40 weeks after the last menstrual period is not evidence-based. This is more accurate than using the last menstrual period because it no longer assumes a Day 14 ovulation.
An ultrasound before 20 weeks is usually more accurate than using the last menstrual period, and the accuracy of an ultrasound is highest if it is done between 11 and 14 weeks. Changes to the estimated due date in late pregnancy should only be made in rare circumstances. Some individuals, such as first-time mothers, are at higher risk for experiencing stillbirth in late pregnancy than other individuals.
Committee opinion no. Obstet Gynecol , American College of Obstetricians and Gynecologists , Reaffirmed Committee Opinion No. Methods for Estimating the Due Date. Ananth, C. A comparison of foetal and infant mortality in the United States and Canada. Int J Epidemiol 38 2 : Baskett, T. BJOG 11 : Boulvain, M. Prospective risk of stillbirth. Randomised trials of earlier induction of labour are needed. BMJ : If you have gone one week past your due date without any signs of impending labour, your doctor will want to closely monitor your condition.
Tests include:. The placenta starts to deteriorate after 38 weeks or so, which means an overdue baby may not get enough oxygen. An overdue baby could also grow too large for vaginal delivery.
Generally, an overdue baby will be induced once it is two weeks past its expected date. Some of the methods of induction include:. This page has been produced in consultation with and approved by:. In Victoria, you can have two types of abortion: surgical and medication.
Both types are safe and reliable. You can have a medication abortion up to nine weeks of pregnancy. You can have a surgical abortion from around six weeks of pregnancy onwards. Pregnant women with asthma need to continue to take their asthma medication as it is important to the health of both mother and baby that the mother's asthma is well managed.
Even if your baby furniture meets every safety standard and recommendation, your child still needs close supervision. The cause of birth defects is often unknown, speak to your GP if you are at increased risk of having a baby with a congenital anomaly. Melissa shares her story of how her baby caught chickenpox at 5 weeks old.
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