“Mayo Clinic Guide to a Healthy Pregnancy” by Myra Wick, M.D., Ph.D., provides valuable insight and information on a wide range of pregnancy-related topics for those who are expecting. This guidebook is the perfect way to learn and prepare for the pregnancy journey. While each pregnancy experience differs, detailed explanations by Mayo Clinic experts are used to describe, clarify, and demystify many possible milestones, scenarios, and potential problems, such as in the following excerpt.
You’ve reached 36 weeks of pregnancy — you’re in the homestretch. Birth may happen at any time now.
However, keep in mind that while pregnancy is officially considered to be 40 weeks, that’s not a guaranteed end date. It often goes even a little longer before your baby arrives.
Here are some key things to know as you prepare to welcome your baby.
Baby’s Growth
In these final weeks, your uterus finishes expanding and your baby gets plump. During the final weeks, weight gain varies, depending on the child. Some babies put on more weight than others.
Week 37
By the end of this week, your baby is considered early term. They aren’t quite done growing yet, but the rate of weight gain is slowing a bit. As your baby’s body builds more fat, it is slowly becoming rounder.
A baby’s sex seems to play some role in determining size at birth. If you have a boy, he’ll likely weigh a bit more than a baby girl born to you at a similar length of gestation.
Week 38
In recent weeks, your baby’s development has focused mainly on improving organ functioning. Your baby’s brain and nervous system are working better every day. This developmental process continues through childhood and even through the teen years. This month, your baby’s brain has prepared to manage the complicated jobs of breathing, digesting, eating and maintaining a proper heart rate.
At 38 weeks into pregnancy, the average baby weighs in at about 7 pounds and is nearing 14 inches long from crown to rump.
Week 39
Almost there — at the end of this week, you’ll have a full-term baby. Baby has now lost most of the vernix and lanugo that used to cover their skin, although you may see traces of them at birth. Your baby now has enough fat laid down under the skin to hold their body temperature as long as there’s a little help from you. This fat gives your baby a healthy, chubby look at birth.
The rest of the body has been catching up, but the head is still the largest part of your baby’s body. That’s why it’s important for your baby to be headfirst in a vaginal birth.
You continue to supply your baby with antibodies — protein substances that help protect against bacteria and viruses. During the first months of life, these antibodies help baby’s immune system stave off infections. Some antibodies are also provided through breast milk. If you haven’t gotten your tetanus, diphtheria and acellular pertussis (Tdap) booster yet (see page 171), now is the time, so that baby will have those protective antibodies after birth.
By this point in pregnancy, babies vary quite a bit in size. A 39-week-old baby typically weighs 6 to 9 ½ pounds.
Week 40
Congratulations! Your due date arrives this week. Most people don’t deliver right on their due dates — only about 4% do, by some estimates — but you’re probably ready to meet your little one. Keep in mind that it’s just as normal to have your baby a week late as it is to have your baby a week early. Try to be patient, although with all the work you’ve done, that may not be easy.
As labor approaches, your baby will experience many changes in order to prepare for birth, including a surge in hormones. This may help maintain blood pressure and blood sugar levels after birth. It may also have something to do with communicating to your uterus that the time has come.
With labor, the blood flow to the placenta will decrease a bit during each contraction. But by now, the baby can tolerate these interruptions so long as they aren’t too frequent and don’t last too long. Your little one is ready for all the amazing changes they will experience at birth.
At 40 weeks, the average baby weighs 7 ½ to 8 pounds and measures about 20 inches long with legs fully extended. Your own baby may be smaller or larger and still be normal and healthy.
Prenatal Checkup
You’ll likely see your healthcare team weekly this month until baby arrives. A routine pelvic exam is not typically part of this checkup, but your healthcare team may check your cervix if they think you may be in the early stages of labor. This exam is reported in numbers and percentages. For example, your healthcare team may tell you that you’re 3 centimeters (cm) dilated and 30% effaced. When you’re ready to push your baby out, your cervix will be 10 cm dilated and 100% effaced.
Don’t put too much stock in these numbers. You may go for weeks dilated at 3 cm, or you may go into labor without any dilation or effacement beforehand. However, measures of your cervix do help your healthcare team determine which medications or methods to use for induction of labor, should you need to be induced.
When to call
During the last month of pregnancy, these signs and symptoms require immediate medical attention:
Vaginal bleeding If you have bright red bleeding of more than a spot or two at any time this month, call your healthcare team right away. It could be a sign of placental abruption, a serious problem in which your placenta separates from the wall of your uterus. This condition is a medical emergency. However, try not to confuse this kind of bleeding with the slight bleeding you may have after a pelvic exam or with the blood and mucus you may see as the cervix thins.
Constant, severe abdominal pain If you have constant, severe abdominal pain, contact your healthcare team immediately. Although uncommon, this can be another sign of placental abruption. If you also have a fever and vaginal discharge along with the pain, you may have an infection.
Decreased movement It’s normal for the vigor of your baby’s activities to decrease somewhat during the last few days before birth. It’s almost as if your baby is resting and storing up energy for the big day. But the number of movements shouldn’t drop a great deal. Decreased frequency of movement may be a signal that something is wrong. To check your baby’s movements, lie on your left side and count how often you feel the baby move. If you notice fewer than four movements in an hour or if you’re otherwise worried about your baby’s decreased movement, call your healthcare team.
Induction at 39 weeks
As a result of recent studies, people with low-risk pregnancies are being offered labor induction at 39 to 40 weeks. Research indicates that inducing labor at this time may reduce several risks, including risks of having a stillbirth, having a large baby (macrosomia) and developing high blood pressure as the pregnancy advances. If you’re considering induction, it’s important that you talk with your health professional to make a decision.
Excerpted from Mayo Clinic Guide to a Healthy Pregnancy by Myra Wick, M.D., Ph.D.
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