Normal Fetal Weight at 29 Weeks Gestation
At 29 weeks gestation, normal fetal weight ranges from approximately 1,100–1,500 grams (2.4–3.3 pounds), with a median around 1,250 grams (2.75 pounds).
Standard Weight Ranges and Percentiles
The 10th percentile threshold at 29 weeks gestation is approximately 1,100 grams, below which a fetus is considered small for gestational age and warrants further evaluation 1.
The 50th percentile (median) fetal weight at 29 weeks is approximately 1,250 grams 2.
The 90th percentile at 29 weeks is approximately 1,500 grams 2.
Fetuses with estimated fetal weight below the 10th percentile have approximately 1.5% stillbirth rate—twice that of normally growing fetuses—and require serial umbilical artery Doppler surveillance 1.
Clinical Context for 29-Week Assessment
At 29 weeks, accurate pregnancy dating is essential before interpreting fetal weight percentiles; dating should ideally be established by first-trimester crown-rump length measurement 1.
Ultrasound biometry at 29 weeks should include biparietal diameter, head circumference, abdominal circumference, and femur length to calculate estimated fetal weight, as multiple parameters improve accuracy over single measurements 3, 2.
The distribution of fetal weight shows asymmetric variation, with wider ranges below the 50th percentile in early gestation and wider ranges above the 50th percentile in late gestation 2.
Important Clinical Considerations
Maternal factors including height, weight, parity, and ethnicity each contribute 1–4.5% variation in fetal weight, though their effects are graded across percentiles 2.
In diabetic pregnancies specifically, a single fetal weight estimate at 29–34 weeks has limited predictive value for identifying large-for-gestational-age infants at term, particularly in women with poor glycemic control 4.
If fetal weight is below the 10th percentile at 29 weeks, umbilical artery Doppler assessment should be performed immediately to differentiate constitutional smallness from pathological growth restriction due to placental insufficiency 1, 5.
Severe fetal growth restriction (estimated fetal weight <3rd percentile, approximately 950–1,000 grams at 29 weeks) carries a stillbirth rate up to 2.5% and requires weekly surveillance with umbilical artery Doppler 1.
Management Based on 29-Week Findings
For fetuses between the 3rd and 10th percentiles with normal umbilical artery Doppler, serial ultrasound every 2 weeks and weekly Doppler assessment are recommended 1, 6.
If absent end-diastolic velocity is detected at 29 weeks, Doppler assessment 2–3 times per week with daily cardiotocography monitoring is required, and delivery should occur at 33–34 weeks 6, 5.
If reversed end-diastolic velocity is present at 29 weeks, immediate hospitalization with cardiotocography 1–2 times daily is mandatory, with delivery recommended at 30–32 weeks 6, 5.
Antenatal corticosteroids should be administered if delivery is anticipated before 33 6/7 weeks, and magnesium sulfate should be given for neuroprotection if delivery is expected before 32 weeks 6.