At 24 weeks pregnant, you’re nearing the end of your second trimester with a baby that weighs about 1⅓ pounds and measures roughly 8¼ inches from crown to rump. This is a significant milestone: your baby is growing rapidly, your body is adjusting to the increasing demands of pregnancy, and a key screening test for gestational diabetes is likely on your calendar.
How Big Your Baby Is Now
Your baby weighs around 630 grams (just over 1⅓ pounds) and measures about 210 millimeters, or 8¼ inches, from the top of the head to the bottom of the torso. That’s roughly the size of an ear of corn. Growth accelerates from here, with your baby putting on weight steadily through the third trimester as fat layers develop under the skin.
The lungs are one of the most important organs still maturing. Cells lining the air sacs are beginning to produce surfactant, a slippery substance that will eventually allow the lungs to inflate properly after birth. The lungs are far from ready to breathe air on their own, but this early surfactant production is a critical first step. Brain development is also ramping up, with increasingly complex neural connections forming, and the inner ear has matured enough that your baby can respond to sounds from outside the womb.
What Viability Means at 24 Weeks
Week 24 is often called the threshold of viability, the point at which survival outside the womb becomes possible with intensive medical care. The reality is still sobering: among babies born between 22 and 24 weeks, only about one in three survive. Outcomes have improved over time. A large study tracking births over more than a decade found that survival rates for extremely preterm infants rose from about 30 percent to 36 percent, with the best improvements seen in babies born at 23 and 24 weeks.
Survival at this stage comes with significant risks. Babies who do survive may face long-term challenges including cerebral palsy, developmental delays, and hearing or vision loss. Even those who appear healthy at age two remain at elevated risk for other health complications later in childhood. Each additional week a baby stays in the womb dramatically improves these odds, which is why recognizing signs of preterm labor matters.
Common Physical Symptoms
Your body is working hard to support a growing baby, and several symptoms tend to show up or intensify around 24 weeks.
Braxton Hicks contractions: You may start to notice mild tightening in your belly that comes and goes. These “practice contractions” are more common in the afternoon or evening, after physical activity, or after sex. They’re irregular, usually painless, and typically ease up when you drink fluids and empty your bladder.
Leg cramps: Cramping in the calves becomes increasingly common as pregnancy progresses, especially at night. Stretching your calf muscles before bed, staying physically active during the day, and drinking plenty of fluids can help prevent them. If a cramp strikes, stretch the affected muscle and try a warm shower, bath, or ice massage for relief. Wearing supportive, low-heeled shoes during the day also helps.
Skin changes: Hormonal shifts increase melanin production, which can cause brown, tan, or gray patches on your face (a condition called melasma) and a dark vertical line down your belly known as linea nigra. Stretch marks, ranging from reddish-brown to silver or purple, may appear on your belly, breasts, buttocks, or thighs. You might also notice tiny spider veins on your face and legs. Most of these changes fade after delivery, though stretch marks tend to lighten rather than disappear entirely.
Sleep and Comfort
Finding a comfortable sleeping position gets harder as your belly grows. You may have heard that sleeping on your left side is the only safe option, but an NIH-funded study found that sleeping on your back or either side through week 30 does not appear to increase the risk of stillbirth, reduced fetal growth, or high blood pressure complications. That’s reassuring if you tend to roll around at night or struggle to stay on your left side.
The concern about back sleeping relates to the growing uterus compressing major blood vessels, specifically the central artery and vein that supply the lower body. This becomes more relevant later in pregnancy. After 30 weeks, the data is less clear, and many providers will recommend side sleeping at that point. For now, sleep in whatever position lets you actually rest. A pillow between your knees or under your belly can ease pressure on your hips and lower back.
The Glucose Screening Test
Between weeks 24 and 28, most pregnant people are screened for gestational diabetes. This one-hour glucose challenge test is straightforward: you drink a sweet syrup containing 50 grams of sugar, wait one hour without eating or drinking anything other than water, and then have your blood drawn.
A blood sugar level below 140 mg/dL is considered a passing result, though some clinics use a lower cutoff of 130 mg/dL. If your result comes back above the threshold, it doesn’t mean you have gestational diabetes. It means you’ll need a longer follow-up test, typically a three-hour version, to confirm or rule out the diagnosis. The syrup tastes very sweet and can make some people feel nauseous, so eating a balanced meal with protein a couple of hours beforehand (before the fasting window begins) may help you feel more comfortable.
Weight Gain by Week 24
How much weight you should have gained by now depends on your pre-pregnancy BMI. During the second and third trimesters, the general target is about one pound per week if you started at a healthy weight, or about half a pound per week if you started overweight or obese. Working backward from that, by week 24 you’ve had roughly 11 weeks of second-trimester gain on top of the 1 to 4 pounds typical for the first trimester.
Total pregnancy weight gain guidelines break down like this:
- Underweight (BMI below 18.5): 28 to 40 pounds total
- Healthy weight (BMI 18.5 to 24.9): 25 to 35 pounds total
- Overweight (BMI 25 to 29.9): 15 to 25 pounds total
- Obese (BMI 30 or above): 11 to 20 pounds total
At 24 weeks, you’re roughly at the midpoint of that steady gain phase. If your weight is tracking above or below these ranges, your provider can help you adjust. What matters most is a consistent pattern of gain rather than hitting an exact number each week.
Warning Signs of Preterm Labor
Because 24 weeks sits right at the edge of viability, knowing the signs of preterm labor is important. Unlike Braxton Hicks contractions, which are irregular and painless, preterm labor contractions come at regular intervals and may feel like persistent belly tightening. Other warning signs include constant pressure in the pelvis or lower belly, vaginal discharge that becomes watery, bloody, or mucus-filled, spotting or light bleeding, and a gush or steady trickle of fluid that could indicate your water has broken.
Any of these symptoms before 37 weeks warrants immediate medical attention. Early intervention can sometimes slow or stop preterm labor, and every additional day in the womb at this stage matters for your baby’s lung and brain development.