At 28 weeks, you are entering your seventh month of pregnancy. This week also marks the official start of the third trimester, the final stretch before delivery. The math can feel confusing because pregnancy months don’t line up neatly with calendar months, but 28 weeks is widely recognized as the beginning of month seven.
Why the Week-to-Month Math Is Confusing
A full-term pregnancy lasts about 40 weeks, which is closer to 10 lunar months (each exactly four weeks) than the nine calendar months people commonly reference. Calendar months vary between 28 and 31 days, so they don’t divide evenly into weeks. That’s why your provider tracks your pregnancy in weeks rather than months, and why you’ll get slightly different answers depending on which conversion chart you use.
The simplest way to think about it: weeks 1 through 4 are month one, weeks 5 through 8 are month two, and so on in four-week blocks. By that count, week 28 lands right at the start of month seven. Most major pregnancy organizations, including Lamaze International, list 28 weeks as seven months.
The Third Trimester Begins
Week 28 is a significant milestone because it marks the beginning of the third trimester. Cleveland Clinic and most major health organizations agree on this cutoff. From here, you have roughly 12 weeks until your due date at 40 weeks, though delivery anywhere from 37 to 42 weeks is considered normal.
This trimester is when your baby gains the most weight and when your body makes its most dramatic final adjustments. Prenatal visits typically become more frequent now, shifting from monthly to every two weeks, and then weekly as you approach your due date.
How Your Baby Is Developing at 28 Weeks
At 28 weeks, the average baby measures about 25 cm (roughly 9.8 inches) from crown to rump and weighs around 1,000 grams, or about 2.2 pounds. That’s roughly the size of a large eggplant.
Lung development hits a turning point this week. Your baby’s lungs have been forming for months, but the substance that keeps the air sacs from collapsing (called surfactant) is mostly produced after week 28. This is one reason why 28 weeks is considered such an important threshold. If a baby were born at this point, survival rates fall between 80 and 90 percent, and only about 10 percent of babies born at 28 weeks experience long-term health problems. Those are encouraging numbers, though every additional week in the womb gives the lungs and brain more time to mature.
Your baby’s eyes can now open and close, sleep-wake cycles are becoming more defined, and you’re likely noticing stronger, more predictable patterns of movement.
What You Might Be Feeling
The third trimester brings a new set of physical changes, and many of them start showing up right around week 28. You’ll probably notice increasing fatigue and discomfort over the coming weeks as your baby grows rapidly.
Heartburn and indigestion are common at this stage because your growing uterus pushes against your stomach while pregnancy hormones relax the valve at the top of your digestive tract. Back pain is another frequent complaint, driven by the extra weight you’re carrying and the loosening of your joints and ligaments. Your ankles, feet, and even your face may start to swell, especially in warm weather.
Other symptoms that commonly appear or intensify around 28 weeks include:
- Sleep problems from difficulty finding a comfortable position
- Round ligament pain on the sides of your belly as your uterus expands
- Stretch marks as your skin stretches more rapidly
- Leg cramps, particularly at night
- Nosebleeds from increased blood volume
- Braxton Hicks contractions, occasional tightening across your belly that comes and goes without a regular pattern
Not everyone experiences all of these, and their intensity varies widely. Some people feel relatively comfortable well into the third trimester, while others find this stretch physically demanding.
Tests and Appointments Around Week 28
A few important screenings cluster around this point in pregnancy. The glucose challenge test, which screens for gestational diabetes, is typically done between 24 and 28 weeks. You drink a sugary solution and have your blood drawn about an hour later to see how your body processes the sugar. If you haven’t had this test yet, your provider will likely schedule it soon.
If your blood type is Rh-negative, you’ll receive an immunoglobulin shot around 28 weeks. This injection prevents your immune system from producing antibodies against your baby’s blood in case your baby has Rh-positive blood. It’s a precautionary measure, and it’s given as a single injection, typically in the arm or hip.
Your provider may also start monitoring your baby’s movement patterns more closely from this point forward. You might be asked to do daily kick counts, tracking how long it takes to feel 10 distinct movements. Most babies reach 10 movements within one to two hours during an active period.
What the Next 12 Weeks Look Like
Between now and your due date, your baby will roughly triple in weight. Most of that gain is fat, which helps regulate body temperature after birth. Your baby’s brain also undergoes rapid development during the third trimester, forming the grooves and folds that characterize a mature brain.
For you, the third trimester is when the physical demands of pregnancy peak. Your blood volume increases significantly, your heart works harder, and your center of gravity shifts forward. Many people find that shorter, more frequent meals help manage heartburn, and that gentle movement like walking or prenatal yoga eases back pain and improves sleep. By around 36 weeks, your baby will likely settle into a head-down position in preparation for birth, and you may feel some relief in your upper abdomen as the baby “drops” lower into your pelvis.