These types of deliveries can save lives. A full-term pregnancy lasts at least 39 weeks. Of course, some babies naturally arrive sooner. And complications during pregnancy can make an early delivery the safest choice. But most babies need 39 weeks to develop fully. Induced or planned delivery before that time—without valid medical reason—is not in the best interest of the baby or the mother. Between and , there were fewer full-term births, and almost twice as many babies born at 37 and 38 weeks.
One reason for this is that it became more common for women to be scheduled for a C-section or to have labor induced before their due date. It may come sooner than you think, especially if you experience a heads-up in the form of your mucus plug or bloody show.
View video transcript. At about seven pounds and 21 inches long on average, your bun in the oven is now a fully cooked loaf of bread.
Wondering where it all goes? Once the vernix and lanugo are shed into the surrounding amniotic fluid your baby ingests them along with other waste products such as bile, urine, and old cells. These all percolate in those teeny intestines, ultimately winding up in his diaper as the very first, very dark green, and very sticky poop known as meconium.
As baby prepares for life in on the outside, the placenta — his lifeline in this underwater world — starts to slowly deteriorate. Not to worry — it still has plenty of life left to sustain your little one until the big day. If you're 38 weeks pregnant, you're in month 9 of your pregnancy. Only a few weeks left to go! Still have questions? Here's some more information on how weeks, months and trimesters are broken down in pregnancy.
Your little one isn't quite so little anymore, weighing about 7 pounds and measuring 20 inches in length, give or take an inch or two. Only two more weeks — four max — before your baby makes her appearance! At 38 weeks pregnant, all systems are almost go! As you prepare for baby's ETA, she's getting ready too, big-time, and continues to shed vernix and lanugo.
Your baby is also swallowing amniotic fluid, some of which winds up in her intestines, where it — along with other shed cells, bile and waste products — will turn into your baby's first bowel movement meconium and perhaps your first diaper change. Her lungs are still maturing and producing more and more surfactant, a substance that prevents the air sacs in the lungs from sticking to each other once she starts to breathe. Most other changes this week are small but important: She's continuing to add fat and fine-tune her brain and nervous system — that way, she can deal with all the stimulation that awaits her once she makes her entrance into the world.
Two weeks and counting — unless, of course, your little bean decides to make a late entrance. Just as your baby is preparing for life outside the womb, at 38 weeks pregnant, your body is tending to its own final touches before the big day.
Some you're aware of, like your baby dropping into your pelvis — easier breathing, more pelvic pressure — and others you're probably not, like cervical dilation and effacement. While you're waiting for your baby to arrive, think of these last weeks as a dress rehearsal for life with your new arrival. Sleepless nights, a little anxiety and leaky breasts.
Leaky breasts? Yes, it's true: Many pregnant women find that they start leaking colostrum — a thin, yellowish liquid that's the precursor to breast milk — sometime in the third trimester. Full of antibodies that protect your newborn, it has more protein and less fat and sugar, which is better for baby's digestive system than the milk that arrives later. If you are leaking colostrum, you may want to consider wearing nursing pads in your bra to protect your clothes — and get used to it, since this is just foreshadowing of what's to come.
Not all women experience it, though. If not, no need to fret — your breasts are still producing colostrum for your baby when the time comes if you plan to breastfeed.
Have visions of yourself, newly delivered domestic goddess, whipping up gourmet meals in those postpartum weeks? Dream on. Cooking will be the last thing on your mind or your to-do list during those first few weeks — or even months — after delivery. To avoid eating cereal for dinner every night, plan ahead. Are you at a healthy weight? Are you taking prenatal vitamins? Exercise regularly and try to eliminate any unnecessary sources of stress from your life. If you have any chronic health conditions, get treated and remain consistent with treatments.
Follow the rules. Eat healthy and get the proper amount of sleep. Exercise regularly be sure to check with your healthcare provider before beginning any new exercise routine during pregnancy. Go to every scheduled prenatal appointment, give an honest and thorough health history to your healthcare provider, and follow their advice.
Protect yourself from potential infections and sickness. Seek medical attention for any warning signs of preterm labor, such as contractions, constant low back pain, water breaking, abdominal cramps, and any changes in vaginal discharge. Wait at least 18 months before trying to conceive again. The shorter the time is between pregnancies, the greater the risk for a preterm delivery, according to the March of Dimes. Talk with your doctor or midwife and stay informed.
Learning as much as you can about the procedures and treatments available to you and your baby will help lower anxieties and give you a sense of control. Keep in mind that the options and support for premature babies have improved over the years, and the odds of leaving the hospital with a healthy baby are higher than ever before. A stroke can be life-threatening, so it's important to act fast. If you think a loved one is having a stroke, here's what you should and shouldn't do.
This is equal to counting forward days from the date of your last period. Another way to look at it is to say that your EDD is 40 weeks after the first day of your last period. In cases where the date of conception is known precisely, such as with in vitro fertilization or fertility tracking where people know their ovulation day, the EDD is calculated by adding days to the date of conception or subtracting 7 days and adding 9 months.
This increases the accuracy of the EDD because it no longer assumes a Day 14 ovulation based on the first day of the last menstrual period. In , a professor from the Netherlands named Hermann Boerhaave explained how to calculate an estimated due date. However, Boerhaave never explained whether you should add 7 days to the first day of the last period, or to the last day of the last period.
In , a professor from Germany named Carl Naegele quoted Professor Boerhaave, and added some of his own thoughts. However, Naegele, like Boerhaave, did not say when you should start counting—from the beginning of the last period, or the last day of the last period. His text can be interpreted one of two ways: either you add 7 days to the first day of the last period, or you add 7 days to the last day of the last period.
Most added 7 days to the last day of the last period. Doctors started using ultrasound in the s. Soon after, ultrasound measurement replaced last menstrual period LMP as the most reliable way to define gestational age Morken et al. A large body of evidence shows that ultrasounds done in early pregnancy are more accurate than using LMP to date a pregnancy.
In a Cochrane review, researchers combined the results from 11 randomized clinical trials that compared routine early ultrasound to a policy of not routinely offering ultrasound Whitworth et al. The researchers found that people who had an early ultrasound to date the pregnancy were less likely to be induced for a post-term pregnancy. In a large observational study that enrolled more than 17, pregnant people in Finland, researchers found that ultrasound at any time point between 8 and 16 weeks was more accurate than the LMP.
There are several reasons why the LMP is usually less accurate than an ultrasound Savitz et al. LMP is less accurate because it can have these problems:.
The authors found that the most accurate time to perform an ultrasound to determine the gestational age was weeks. This was a more accurate result than any of the other ultrasound scans, and more accurate than the LMP. The accuracy of the ultrasound saw a significant decline starting at about 20 weeks.
Using an estimated due date from either the LMP or an ultrasound at weeks led to a higher rate of pre- and post-term births.
Ultrasounds in the third trimester are less accurate than earlier ultrasounds or the LMP at predicting gestational age. All babies are about the same size early in pregnancy. The reverse is also true for babies that will be smaller than average at term—their due date might be moved to a later date. This could be risky if the baby is experiencing growth restriction, as growth-restricted babies have a higher risk of stillbirth towards the end of pregnancy.
Because of these problems with third trimester ultrasounds, the American College of Obstetricians and Gynecologists states that due dates should only be changed in the third trimester in very rare circumstances In the U.
In the past, researchers figured out the average length of a normal pregnancy by looking at a large group of pregnant people, and measuring the time from ovulation or the last menstrual period, or an ultrasound until the date the person gave birth—and calculating the average. However, this method is wrong and does not give us accurate results.
This method does not work because many people are induced when they reach 39, 40, 41, or 42 weeks. If you do include these induced people in your average, then you are including people who gave birth earlier than they would have otherwise, because they were not given time to go into labor on their own. But this puts researchers in a bind, because if you exclude a person who was induced at 42 weeks from your study, then you are ignoring a pregnancy that was induced because it went longer—and by excluding that case, you artificially make the average length of pregnancy too short.
There have been two studies that measured the average length of pregnancy using survival analysis:. 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. In , Jukic et al. This was a smaller study—there were only healthy women, and they all gave birth between the years and However, this was also an important study, because researchers followed the participants even before conception and measured their hormones daily for six months Jukic et al.
This means that the researchers knew the exact days that the participants ovulated, conceived, and even when their pregnancies implanted! After excluding women who had preterm births or pregnancy-related medical conditions, the final sample of women had a median time from ovulation to birth of days 38 weeks, 2 days after ovulation. The median time from the first day of the last menstrual period to birth was days or 40 weeks, 5 days after the last menstrual period.
The length of pregnancy ranged from 36 weeks and 6 days to one person who gave birth 45 weeks and 6 days after the last menstrual period.
The 45 weeks and 6 days sounds really long… but this particular person actually gave birth 40 weeks and 4 days after ovulation. Her ovulation did not fit the normal pattern, so we know her LMP due date was not accurate. Women who had embryos that took longer to implant were more likely to have longer pregnancies. Also, women who had a specific sort of hormonal reaction right after getting pregnant a late rise in progesterone had a pregnancy that was 12 days shorter, on average.
Instead, it would be more appropriate to say that there is a normal range of time in which most people give birth. About half of all pregnant people will go into labor on their own by 40 weeks and 5 days for first-time mothers or 40 weeks and 3 days for mothers who have given birth before. The other half will not. In , Oberg et al. They found that genetics has an incredibly strong influence on your chance of having a birth after 42 weeks:.
Overall, researchers found that half of your chance for having a post-term birth comes from genetics. The risks of some complications go up as you go past your due date, and there are at least three important studies that have shown us what the risks are. In their study, Caughey et al. However, when the researchers used a statistical method to control for the use of interventions, the risks still increased with gestational age.
For more information about meconium, see this article by Midwife Thinking about meconium stained waters. In this section, we will talk about how the risk of stillbirth increases towards the end of pregnancy. 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.
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