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Pregnancy Week 40

What to expect when you’re 40 weeks pregnant

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Written by Jennifer Wise
Edited by Justin Martino

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    Baby development at 40 weeks pregnant

    Your baby is now fully formed, and you are probably fully ready to meet them. Don’t attempt anything drastic to hasten labor if your due date comes and goes without a newborn to show for it. (Only 5% of babies arrive on their estimated due date!) Check that your hospital bag is packed and be sure you have important phone numbers — like your obstetrician’s office and the numbers of those you want with you at the hospital — handy.

    Every term pregnancy varies, but, if your baby is very typical, they measure between 19 and 21 inches and weigh approximately 7.6 pounds. This is about the size of a watermelon!

    A healthy newborn will have around 300 bones, many made entirely of flexible cartilage. Some will ossify, hardening into bone, and other bony segments will fuse together as they mature. As an adult, they will have 206 bones.

    No matter what number the scale reads for your newborn’s weight, their weight has increased 6 billion times since they were a microscopic fertilized egg!

    Your baby’s body composition is probably 12% to 16% fat, which helps keep them warm. Of your baby’s lean body mass, about 80% is water. The rest is composed of protein and glycogen (and sugar and spice and everything nice).

    Your baby’s birth weight is more strongly related to your weight before you were pregnant than the weight you’ve gained during pregnancy. Babies also tend to be within the weight range their parents were as newborns.

    Week 40 pregnant belly

    At 40 weeks, it may feel as if your entire body is your womb and its contents. Your uterus alone has multiplied in weight by a factor of 20 — from about 2 ounces to around 2.5 pounds! You’re carrying about a quart of amniotic fluid, a full-term infant and a placenta, which is approximately 88% water.

    While the weight of your placenta will vary according to the size of your uterus, it will likely appear (once you see it, if that’s part of your plan) approximately one inch thick, round and flat. The side that’s implanted in your uterine wall will appear rough and bloody. The side nearest your baby is covered by the amniotic membrane and is shiny, pale and smooth.

    Common pregnancy symptoms at 40 weeks

    Who’s ready with the scissors? Your umbilical cord, which has two arteries and one vein, probably measures 12 to 39 inches when it’s pulled straight from its corkscrew-like figuration. It often isn’t problematic if the cord wraps around your baby’s neck unless the cord is compressed during labor or delivery. If this happens, a cesarean section might be necessary.

    • Contractions: Prelabor uterine contractions will become more frequent now. They’ll increase the circulation in your uterus, push the baby against your cervix and help thin and soften your cervix.
    • Lower back pain: Lower back and hip pain may bother you more now. As hormones prepare your body for the baby to make their way down the birth canal, the connective tissue in your pelvic region will loosen. Walking, stretching or taking a warm bath may alleviate the pain. Move in whatever way your body tells you to.
    • Sexual activity: Unless your obstetrician has advised you to avoid intercourse, you’re in the clear even at week 40 to have sex with your partner whenever and in whatever way feels best to you.
    • Anxiety: If you’re feeling anxious about potential labor pain and the safe delivery of your baby, you’re not alone. Giving birth is a big deal. Try to find a trusted ally you can bounce your feelings off of and have with you in the delivery room — it can really help!

    Pregnancy checklist at 40 weeks pregnant

    Your body — womb, heart and every other part — has accomplished a feat as unique as it is universal. You’ve produced, and will soon deliver, a new human being into the world.

    Reminders for
    Week 40
    • Know the signs of labor. Signs of labor can include contractions, back pain, membrane rupture, diarrhea, vaginal bleeding, a sensation of warmth in your abdomen and/or lower abdominal pressure. Unless labor is cut short by a C-section, you’ll go through three phases of increasing intensity: latent or early labor, active labor and transitional labor. And then: Baby!
    • Channel your anxiety. If you’re feeling anxious, it may help to redirect your energy toward a more productive end. Ask someone who lives near you to set up a meal train or prepare dishes for your freezer stash, have a long pre-baby conversation with a friend or find a way to connect with your partner or a loved one that your post-pregnancy life won’t allow for a while.
    • Late-term babies. Beyond 42 weeks’ gestation, about 20% of babies develop postmaturity syndrome. If you’re a week or two after your due date, and if you and your obstetrician determine that all’s well, your pregnancy will continue. In some cases, however, testing may reveal that a postdate placenta isn’t functioning optimally, that the amniotic fluid is decreasing and/or that the baby is showing signs of distress. Under such circumstances, your obstetrician will either induce labor or perform a C-section.

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    Week 39

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