How Big Is a Baby at 38 Weeks? What to Expect in the Final Stretch
The average baby weighs between 2.9 and 3.2 kg (6.6 and 7 pounds) and is between 47 and 50 cm long by week 38. However, each baby develops at its own rate, just like adults do. The majority of full-term babies born at this stage fall within a healthy range in weight, though some may weigh slightly more or less.
Every baby is unique, and a number of important factors influence their birth weight. Although genetics is a factor, environmental factors can have a significant effect on fetal development in the womb.
Baby’s Growth at 38 Weeks: Key Facts
| Category | Measurement at 38 Weeks |
|---|---|
| Average Weight | 2.9 – 3.2 kg (6.6 – 7 lbs) |
| Average Length | 47 – 50 cm (18.5 – 19.7 inches) |
| Head Circumference | ~34 cm (13.4 inches) |
| Body Development | Fat accumulation around knees, elbows, and shoulders |
| Lung Development | Producing surfactant to help with first breaths |
| Digestive System | Contains meconium (baby’s first bowel movement) |
| Movement | Regular but slightly reduced due to limited space |
Reference Source: BabyCenter
What Influences a Baby’s Weight at 38 Weeks?
Every baby is unique, and a number of important factors influence their birth weight. Although genetics is a factor, environmental factors can have a significant effect on fetal development in the womb.
Factors That Affect Baby’s Weight at 38 Weeks
- Parental Genetics – Taller or larger parents tend to have heavier babies.
- Maternal Diet – A nutrient-rich diet supports steady fetal weight gain.
- Placental Health – A well-functioning placenta ensures optimal growth.
- Gestational Diabetes – Often leads to higher birth weights (macrosomia).
- Multiple Pregnancies – Twins or triplets usually weigh less than singletons.
- Maternal Health Conditions – Issues like hypertension or preeclampsia can slow fetal growth.
Concerns about whether your baby is growing at a healthy rate can be allayed by being aware of these factors.
Is 38 Weeks Considered Full-Term?
Indeed! Your baby is officially full term at 38 weeks, and a safe, trouble-free delivery is possible. Many doctors believe that babies born between 37 and 40 weeks are fully developed, even though 40 weeks is still the gold standard.
How Does Baby’s Weight Compare to Previous Weeks?
The last month has seen a noticeable acceleration in your baby’s weight gain. They probably weighed between 2.1 and 2.5 kg at 34 weeks, which was just four weeks ago. They have gained between 400 and 700 grams by 38 weeks, preparing for life beyond the womb.
These last-minute fat reserves offer vital energy reserves and aid in controlling body temperature after birth.
What If My Baby Is Smaller or Larger Than Expected?
Some babies may weigh as little as 2.5 kg or as much as 4 kg, although the majority weigh between 2.9 and 3.2 kg. Here’s when medical professionals may step in:
- Under 2.5 kg – Could indicate intrauterine growth restriction (IUGR), requiring closer monitoring.
- Over 4 kg – May suggest macrosomia, often linked to gestational diabetes, which can increase the chance of a C-section.
To evaluate fetal growth, doctors use fundal height measurements and ultrasound scans. They might suggest an early induction or more testing if the baby is noticeably bigger or smaller.
How Can You Support a Healthy Baby Weight?
Birth weight is mostly determined by genetics, but some lifestyle decisions can maximize fetal growth. These consist of:
- Eating nutrient-rich meals with protein, healthy fats, and fiber.
- Staying hydrated to maintain amniotic fluid levels.
- Engaging in safe prenatal exercises to improve circulation.
- Attending regular prenatal check-ups to track growth trends.
- Monitoring fetal movements to ensure your baby remains active.
Does Baby Movement Change at 38 Weeks?
Yes, but there should still be regular movement. Movements may feel less like jabs and more like rolls and stretches because the baby has less space to kick. At least ten movements per hour should still be felt, though.
Contact your healthcare provider right away if you observe a sudden decrease in fetal movement, as this could be a sign of fetal distress.
What Happens If You Deliver at 38 Weeks?
Unless there are further complications, babies born at 38 weeks are usually considered full-term and do not need NICU support. The majority will have fully formed reflexes, latch onto breastfeeding, and breathe on their own.
What to Expect If Your Baby Arrives This Week
- They will likely weigh between 2.9 – 3.2 kg, but some may be heavier or lighter.
- Their lungs are fully mature, reducing respiratory risks.
- They will shed any remaining lanugo (fine body hair).
- They will be alert, with strong reflexes for feeding and grasping.
