What to Expect When Your Baby is LGA (Large for Gestational Age)
Hearing that your baby is measuring large for gestational age (LGA) during pregnancy can bring up all kinds of feelings—surprise, worry, curiosity, maybe even pride. It’s not uncommon; in most cases, both mom and baby do just fine. Still, it helps to understand what LGA means, why it happens, and how it might shape your birth experience.
Let’s walk through it all together—from definition to delivery and beyond.
What Does “Large for Gestational Age” Mean?
“Large for gestational age,” or LGA, is a term used when a baby’s weight is above the 90th percentile for their gestational age. In other words, your baby weighs more than 90% of other babies at the same point in pregnancy. This is typically estimated through ultrasound measurements of the baby’s head, abdomen, and femur length.
After birth, a baby is also considered LGA if their weight is over 4,000 grams (8 lbs, 13 oz) or 4,500 grams (9 lbs, 15 oz), depending on clinical guidelines and risk factors.
Why Is My Baby Measuring Big?
There are several reasons your baby might be measuring large, and often, it’s a combination of factors:
- Genetics: If you or your partner were big babies or have had a larger baby before, this may be hereditary.
- Maternal Diabetes: Both pre-existing and gestational diabetes can lead to higher glucose levels in the womb, causing the baby to store more fat and grow larger.
- Excessive Maternal Weight Gain: Gaining significantly more weight than recommended during pregnancy can contribute to fetal overgrowth.
- Post-term Pregnancy: Babies who stay in the womb longer than 40 weeks may continue to grow, sometimes quickly.
- Male Babies: Statistically, male babies tend to be larger than female babies.
- Multiparity: Women who have had multiple children may experience larger babies with each pregnancy.
How is LGA Diagnosed?
Diagnosis can happen during pregnancy or after birth. During pregnancy, LGA may be suspected if:
- Your fundal height (the size of your uterus) measures larger than expected
- Ultrasounds estimate your baby’s weight above the 90th percentile
- There are signs of excess amniotic fluid (polyhydramnios), which can sometimes accompany LGA babies
Ultrasounds are helpful tools, but not perfect—there’s often a margin of error of up to a pound (0.5 kg), especially in later pregnancy. This means some babies considered LGA prenatally are average size at birth, and vice versa.
What to Expect During Pregnancy
If your baby is suspected to be LGA, your care team may recommend additional monitoring and steps to support a healthy outcome. These may include:
- More frequent ultrasounds to track growth patterns
- Screening for gestational diabetes if it hasn’t already been done
- Monitoring for signs of preeclampsia or high blood pressure, which can sometimes accompany LGA pregnancies
- Discussion of your birth plan, especially around the timing and method of delivery
Depending on your specific case, your provider may also advise lifestyle changes, including nutritional counseling, increased physical activity, or even early delivery.
What It Means for Labor and Delivery
A larger baby doesn’t necessarily mean a complicated birth—but it’s something your provider will consider when helping you plan for labor. Here are some potential implications:
Vaginal Birth
Many LGA babies are born vaginally without complications. However, larger babies can:
- Take longer to descend into the birth canal
- Lead to more prolonged or more difficult labors
- Increase the risk of perineal tearing or need for episiotomy
- Present the risk of shoulder dystocia, a condition where the baby’s shoulders get stuck after the head is delivered (this is a medical emergency but is typically well-managed by trained providers)
Cesarean Birth
Your provider might discuss the option of a cesarean delivery (C-section), especially if:
- The estimated fetal weight is above 5,000 grams (11 lbs) in a person without diabetes or 4,500 grams (9.9 lbs) in a person with diabetes
- You had complications with previous LGA births
- Baby’s growth is accelerating rapidly in the final weeks
Ultimately, decisions are made based on your health, the baby’s position and size, and preferences.
What to Expect After Birth
Once your LGA baby arrives, they may need a little extra attention in those early hours and days. Your care team will watch for:
- Hypoglycemia (low blood sugar): Larger babies, especially those born to mothers with diabetes, may have trouble regulating blood sugar at first
- Jaundice: Bigger babies have a slightly higher risk of jaundice, a yellowing of the skin due to bilirubin buildup
- Birth injuries: Bruising, broken collarbones, or nerve issues (like Erb’s palsy) can happen with difficult births, but are rare
- Feeding difficulties: Some larger babies can be sleepy or slow to latch at first, so early lactation support is helpful
Many LGA babies are perfectly healthy and go home on a typical schedule—these are just things your provider will monitor to ensure a smooth start.
How to Prepare and Support Yourself
Being told your baby is measuring big doesn’t mean something is wrong—it just means you and your care team need to be thoughtful and informed. Here’s how to take care of yourself:
- Attend all prenatal appointments and follow through with recommended testing
- Ask questions about your provider’s plan if your baby continues to grow quickly
- Learn about your birth options, including vaginal delivery and C-section
- Talk to a lactation consultant before birth, especially if you’re hoping to breastfeed
- Build a support team—partner, doula, family, friends—who can be there for you before, during, and after delivery
- Practice mindfulness or stress-relief techniques to stay calm and grounded
If your baby is LGA, you’re not alone—this is a fairly common diagnosis. With attentive prenatal care, open communication with your provider, and some preparation, you can feel empowered and ready for the journey ahead.
Your body is doing something incredible. And no matter how your baby is born, the love, care, and connection that follow are what matter most.
