Six months pregnant corresponds to roughly weeks 21 through 24 of pregnancy, though some sources extend it through week 27. The confusion is understandable: pregnancy lasts 40 weeks, which doesn’t divide neatly into nine calendar months. That mismatch is why doctors track pregnancy in weeks rather than months, and why you’ll get slightly different answers depending on who you ask.
Why Months and Weeks Don’t Line Up
Most people assume nine months equals 36 weeks (nine times four), but a full-term pregnancy is 40 weeks. The gap exists because calendar months aren’t exactly four weeks long. Most months have 30 or 31 days, which adds an extra two or three days beyond four perfect weeks. Over nine months, those extra days add up to roughly four additional weeks.
This is why your doctor will never ask how many months along you are. Weeks are precise. Months are approximations. When someone says they’re “six months pregnant,” they could mean anywhere from week 21 to week 28 depending on how they’re counting. Cleveland Clinic defines month six as weeks 21 through 24, while other pregnancy calendars place weeks 25 through 28 in the sixth month. The most common breakdown puts the start of your sixth month at week 24, with weeks 25 through 28 finishing it out.
A practical way to think about it: at six months, you’re near the end of your second trimester, which wraps up around week 27 or 28.
What’s Happening With the Baby
Wherever you land in the week 21 to 28 range, this stretch is packed with developmental milestones. The baby’s skin is reddish and wrinkled, with veins visible through translucent skin. Eyelids begin to part, and the baby starts responding to sounds by moving or with a faster heartbeat. You may notice more regular, jerky movements as the baby becomes increasingly active.
Around week 23, rapid eye movements begin. By week 26, the lungs start producing surfactant, a substance that allows the air sacs to inflate properly and is essential for breathing after birth. By week 27, the baby can open its eyes and blink. These lung and eye developments are among the reasons this period marks a critical transition toward viability outside the womb.
The Viability Milestone
Week 24 carries special significance in obstetric care. Before 24 weeks, a baby born prematurely generally has less than a 50 percent chance of survival. At 24 weeks, that survival rate rises to between 60 and 70 percent, though about 40 percent of those infants will face long-term health complications from being born so early. This is why 24 weeks is often called the threshold of viability, and it’s one reason your care team pays close attention to this stretch of pregnancy.
What You Might Be Feeling
Around six months, many women start noticing Braxton Hicks contractions for the first time. These feel like mild menstrual cramps or a random tightening across the front of your belly. They’re irregular, unpredictable, and never become intensely painful. If you change positions or take a walk, they typically ease up. The key distinction from real labor contractions is that Braxton Hicks don’t get closer together over time, and you can still walk, talk, and go about your day through them.
Your belly is noticeably larger now, and weight gain picks up. For someone who started pregnancy at a healthy weight, the recommended gain during the second and third trimesters is between half a pound and one pound per week. You may also notice increased back pain, swelling in your feet, and trouble sleeping as the baby takes up more space.
The Glucose Screening Test
One medical appointment that lands squarely in the sixth month is the glucose screening test, typically scheduled between weeks 24 and 28. This test checks for gestational diabetes, a condition where blood sugar levels become elevated during pregnancy. You’ll drink a sugary liquid, wait an hour, and have your blood drawn. If the initial screening comes back high, a longer follow-up test confirms whether gestational diabetes is present. It’s one of the most routine tests in prenatal care at this stage.
A Simple Reference Chart
- Month 4: Weeks 14–17
- Month 5: Weeks 18–22
- Month 6: Weeks 23–27
- Month 7: Weeks 28–31
- Month 8: Weeks 32–35
- Month 9: Weeks 36–40
These ranges shift slightly depending on the source, which is exactly why weeks are the more reliable way to track your pregnancy. If someone asks how far along you are, giving your week count will always be more accurate than naming a month.