It's getting crowded in there
How baby grows
Now baby weighs almost 6.5 pounds and her total length is about 21 inches long. But she hasn't stopped growing yet; she'll continue to develop about a half ounce of fat a day. Still, overall growth does slow from here on out. That's fortunate since there is very little available space left in the womb.
Here are a few final developments taking place in week 37:
- Immune system. It continues to strengthen and will continue to get stronger after birth yet will not be completely functional until early adulthood.
- Dexterity. Your baby can now grasp with her fingers as dexterity improves.
How you change
- Vaginal discharge. You may experience heavier vaginal discharge this week, with more cervical mucus in it. Sometime during this week, as the cervix dilates in preparation for the labor, you may experience "bloody show." This thick, yellow, blood-streaked mucus plug had sealed off your uterus from infection and bacteria. As your cervix thins, it may drop out.
- Although some women never notice its departure, you may see thick discharge or stringy mucus tinged with blood. This light vaginal bleeding is considered to be an early sign of impending labor and can occur a few weeks, days or hours before contractions begin. Actual bleeding from the vagina, however, is abnormal and should be reported to the doctor immediately.
- Pelvic exam. At about this time your doctor may also perform a pelvic exam to evaluate your progress. To check for impending labor, some doctors may look for leaking amniotic fluid and examine your cervix to see whether it has softened or thinned out.
Slowing down growth as the big day approaches
How baby grows
Although your baby's growth is slowing, fat will continue to accumulate, providing a thicker blanket of insulation in preparation for her entry into the outside world.
Your baby may weigh almost 7 pounds this week, but at a length of about 21 inches, she hasn't grown much taller. The average full-term newborn weighs from 6 to 9 pounds and is 18 to 21 inches long.
Here are some other developments this week:
- Meconium (baby's feces). It will continue to build up in her intestines.
- Head. By now the circumference of your baby's head and abdomen are about the same.
How you change
- More bathroom breaks. As your baby puts more pressure on your bladder this week, your need to urinate increases.
- How big is the baby? Since you're probably visiting your doctor on a weekly basis, you can ask for an estimate of the exact size of your baby.
Good to know
At this point, an ultrasound can provide a fairly accurate estimate of fetal weight by measuring the diameter and circumference of your baby's head and abdomen, and the length of the leg bone. But remember, this estimate can't predict how easily the baby will fit through your pelvis and the birth canal. Your doctor usually won't be able to tell whether your baby will move easily down the birth canal until labor actually begins.
How baby grows
Even as late as the 39th week, there's one part of your baby's body that hasn't quite finished developing: the two soft spots on her head called the fontanels, where the skull bones haven't yet joined together. These areas allow the flexible skull bones to bend without damaging the brain as your baby travels down the birth canal.
Because of the strength of contractions during labor, many newborn heads look elongated or cone-shaped right after birth. The bones will return to their round shape within a few days after birth. During your baby's first year, the skull will harden; by 18 months the soft spots will have completely hardened.
Your baby’s skeleton also continues to develop. She now has 300 bones (about 100 more than an adult does, since some bones fuse together as the child grows).
How you change
- Weight gain. Your pregnancy weight probably won't increase too much more from this point forward.
- Contractions. Your body is preparing itself for labor, and you may begin experiencing Braxton Hicks contractions, which can be as strong as real contractions. Unlike real labor, these contractions are irregular and tend to stop and start.
- Although false contractions feel real, they aren't strong enough to make the cervix start thinning out or dilating. They may wax and wane for days or a few weeks before the onset of true labor. It can be hard to differentiate true and false labor, but contractions of true labor tend to get progressively stronger and more regular.
- Water break. Another sign of labor—the rupture of your amniotic sac (water breaking)—could happen at any moment. When water breaks, the sensation you may feel can range from a startling gush of water to a steady trickle. Some women never notice their water breaking at all.
You may be ready to deliver this week. The average size of a baby born at 40 weeks is about seven pounds eight ounces.
How your baby has grown
The average birth weight for babies born at 40 weeks is about 7 pounds 8 ounces, and the average length is about 21 inches.
There are a number of surprising physical characteristics you may notice upon your little one's arrival. You may not have realized how your hormones can affect your baby at this stage. Because of the presence of your hormones in your baby's system, your baby's genitals (scrotum in boys and labia in girls) may appear enlarged. Your baby boy or girl may secrete milk from their tiny nipples. This is another hormone-related occurrence that should disappear in a few days and is completely normal. Finally, hormones may cause some "infant acne" pimples on your baby's face. These too will disappear within a month or so of birth.
- Skin. Baby's skin can be very sensitive. When your baby is born it's normal for her to have skin discoloration; blotchy, dry skin; or even rashes.
- Head shape. Your baby's trip through the birth canal will temporarily elongate her tiny head; this will round out within a few days.
- No tears. Babies can cry at birth, but they are born with an underdeveloped tear duct system. You may notice that tears don't appear until 1 to 3 months of age.
- Umbilical cord. After the cord is cut, a remnant will remain attached to the baby's abdomen. It will drop off within the first month
How you have changed
When you're ready to deliver, you'll experience the following three basic stages of labor:
First stage: Your uterus contracts at regular intervals, thinning and stretching your cervix. This stage lasts the longest because the cervix must widen from zero to 10 centimeters.
The average duration of first-stage labor in women experiencing their first labors is about 12 hours. For moms who have experienced labor and delivery before, it may be half that long. However, first-stage labor can range from much shorter to much longer and still be considered normal.
Second stage: This is the time your baby moves through the vaginal canal and out of your body, due to a combination of uterine contractions and your pushing efforts. It usually lasts an hour or two with the first birth, but can be much shorter with later ones.
Third stage: The final stage of labor occurs when you deliver the placenta. After the baby has been delivered, the placenta separates from the uterine wall within about 10 minutes. Your doctor will massage your abdomen to help move the placenta along. Your doctor may need to reach inside and remove the placenta if it isn't expelled on its own.