What are warning signs at 31 weeks pregnant?

Severe headache that won't go away with acetaminophen — preeclampsia.; Vision changes — blurred vision, light flashes, vision loss.; Severe right-upper-quadrant pain — HELLP syndrome.; Sudden swelling of face, hands, or feet.; Reduced fetal movement — fewer than 10 kicks in 2 hours.; Vaginal bleeding, fluid leakage, or persistent contractions.; Severe shortness of breath at rest or chest pain.; Fever over 100.4°F.; Seizure — eclampsia, life-threatening.;

Third trimester · Pregnancy week by week

Week 31 of pregnancy

Q: How big is the baby at 31 weeks?

size of a coconut. The fetus is now 16 inches long. Lanugo begins to shed. Fingernails reach the fingertips. Lungs continue maturing.

Baby is the size of a coconut. About 16.20 inches, 1500g.

By week 31, the fetus weighs about 1.5 kg. Black women have higher rates of late-pregnancy hospitalizations — confirm your delivery hospital is in-network and ready. Source

What's happening with the baby

The fetus is now 16 inches long. Lanugo begins to shed. Fingernails reach the fingertips. Lungs continue maturing.

What's happening for you

Bump is heavy. Many women have lower back pain, sciatica, or pelvic-girdle pain. Sleep is increasingly disrupted. Breast colostrum production may increase.

Common (normal) symptoms this week

Lower back pain, sciatica, pelvic pain, breast colostrum leaking, sleep disturbance, increased Braxton Hicks, mild edema.

Call your OB or 911 if

Severe headache that won't go away with acetaminophen — preeclampsia.
Vision changes — blurred vision, light flashes, vision loss.
Severe right-upper-quadrant pain — HELLP syndrome.
Sudden swelling of face, hands, or feet.
Reduced fetal movement — fewer than 10 kicks in 2 hours.
Vaginal bleeding, fluid leakage, or persistent contractions.
Severe shortness of breath at rest or chest pain.
Fever over 100.4°F.
Seizure — eclampsia, life-threatening.

Why this week matters for Black families

The third trimester carries the highest Black-maternal-mortality risk in the U.S. obstetric data. Preeclampsia, HELLP syndrome, and preterm labor are most common here. The CDC Pregnancy Mortality Surveillance System repeatedly cites delayed recognition of severe symptoms in Black women as a contributor to preventable deaths. This is the window where you advocate hardest. If the OB's office tells you a symptom 'sounds like normal pregnancy,' ask: 'Can you document in the chart that I reported this and that you decided not to evaluate it further?' That sentence alone reverses outcomes in documented case reviews.

What to do this week

Pre-register at delivery hospital. Continue BP tracking. Schedule home visit from doula or postpartum support if you have one. Begin pumping practice if planning to breastfeed.

Pregnancy / baby

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References

AHRQ HCUPnet — Maternal Hospitalizations by Race.
USDA WIC Breastfeeding Resources.

Last medically reviewed: April 25, 2026.

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