The last month of pregnancy, roughly weeks 36 through 40, brings rapid changes for both you and your baby. Your body is preparing for labor in ways you can feel, your baby is gaining weight fast, and your prenatal visits will pick up in frequency. Here’s what’s actually happening and what it all feels like week by week.
How Your Baby Is Growing
By week 36, your baby’s skin is smoothing out as fat accumulates underneath it, and the limbs start to look chubby. Most babies have turned head-down by this point. If yours hasn’t, your provider will likely discuss options for repositioning the baby around week 37.
By week 38, the baby’s head and belly circumference are roughly equal, and the fine body hair (lanugo) that covered the skin earlier in pregnancy is mostly gone. Weight at this stage is typically around 6.5 pounds, though some babies are already close to 9 pounds. In the final two weeks, fat continues to build up across the body to help regulate temperature after birth. The chest gets larger, and by week 40, the average baby weighs about 7.5 pounds with a crown-to-rump length of around 14 inches. Healthy babies come in a wide range of sizes, so these are rough benchmarks rather than targets.
Lightening: When the Baby Drops
At some point during the last month, the baby settles deeper into your pelvis. This is called lightening or “dropping,” and it physically changes the shape of your belly. If this is your first baby, it usually happens two to four weeks before delivery. If you’ve given birth before, it may not happen until labor itself begins.
The trade-offs are immediate. Breathing gets easier and heartburn often lets up because there’s less pressure on your diaphragm and stomach. But the new downward pressure on your bladder means more frequent trips to the bathroom. Some people also notice increased pelvic pressure or a waddling feeling when they walk.
Common Physical Symptoms
Sleep becomes harder. Many providers recommend sleeping on your left side during late pregnancy. The reasoning is that as the uterus grows heavier, lying flat on your back can compress major blood vessels, potentially reducing blood flow to the placenta. A pillow between your knees or under your belly can help you stay comfortable on your side through the night.
Your breasts may start leaking colostrum, the thick, yellowish first milk your baby will eat after birth. Your body actually started producing it between weeks 12 and 18, but visible leaking is more common now. By around week 37, colostrum can typically be hand-expressed. Some people leak noticeably; others don’t leak at all. Both are normal.
Braxton Hicks contractions, the “practice” contractions you may have been feeling for weeks, can become more frequent. They feel like a tightening across your abdomen or mild menstrual cramps. They’re irregular, don’t get progressively stronger, and usually stop if you change positions, drink water, or rest. Being dehydrated, very active, or needing to urinate can all trigger them.
Prenatal Visits and Testing
Your appointment schedule picks up noticeably. Starting at week 36, most providers want to see you every one to two weeks until delivery, compared to every two to four weeks earlier in the third trimester.
One key test happens between weeks 36 and 38: the Group B Strep (GBS) screening. A swab is taken from the vagina and rectum and sent for a culture. About 1 in 4 pregnant people carry this bacteria, which is harmless to adults but can cause serious infection in newborns during delivery. If you test positive, you’ll receive antibiotics through an IV once labor starts. If you’re having a planned cesarean and your water hasn’t broken, antibiotics during delivery aren’t typically needed, but you’ll still be tested because labor can begin unexpectedly.
Your provider may also begin checking your cervix during these visits. They’re looking at two things: effacement (how thin the cervix has gotten) and dilation (how wide the opening is). The cervix needs to reach 10 centimeters of dilation for delivery. During an exam, your provider uses two fingers to estimate the opening. One finger width is roughly 1 centimeter, two fingers side by side is about 3 centimeters. It’s common to be 1 or 2 centimeters dilated for days or even weeks before labor actually begins, so early dilation on its own doesn’t predict when you’ll deliver.
Tracking Your Baby’s Movement
Kick counts become especially important in the final month. The standard approach is to pick a time when your baby is usually active, sit or lie down, and count how long it takes to feel 10 movements. Kicks, rolls, flutters, and swishes all count. You’re looking for 10 movements within two hours. Most babies hit that number well within one hour.
If two hours pass without 10 movements, contact your provider. It doesn’t necessarily mean something is wrong, but a slowdown in movement is one of the few signals your baby can send you, and it’s worth checking promptly.
Telling Real Labor From False Alarms
Knowing the difference between Braxton Hicks and real labor contractions saves a lot of unnecessary hospital trips. Real labor contractions are consistent and get stronger, longer, and closer together over time. You’ll have trouble talking or walking through them. Braxton Hicks are irregular, stay about the same intensity, and ease up when you move around or hydrate.
Real contractions also last between 30 and 90 seconds each. The widely used guideline for when to head to the hospital is the 5-1-1 rule: contractions coming every 5 minutes, each lasting 1 minute, and this pattern continuing for at least 1 hour. Other reasons to go in immediately include your water breaking, heavy vaginal bleeding, or a sudden decrease in fetal movement.
What to Have Ready
Since labor can start anytime from week 37 onward (considered full term), having your hospital bag packed and your car seat installed by week 36 removes a layer of stress. Beyond the practical logistics, this is a good time to finalize your preferences for labor and delivery with your provider, including pain management options and who you want in the room.
The last month feels long because the physical discomfort is real: disrupted sleep, frequent urination, pelvic pressure, and contractions that may or may not mean anything yet. But each of those symptoms is a sign that your body is doing exactly what it needs to do to prepare for delivery.