Day 219 of 280 · 31 weeks + 2 days
The mattress
Last reviewed · 2 min read · 6 sources · Plain-text version
Thirty-one weeks and two days. A borrowed crib can be a fine crib, but the mattress matters most. Today you check it fits snugly and stays very firm.
- Size this week
- about the size and weight of a coconut
- Length this week
- around 41.1 cm from head to heel

Thirty-one weeks and two days. Of all the baby gear on the list, the crib mattress is the one worth checking with your own hands. Today you do that.
Your baby

Your body
Getting a crib, carry cot, or Moses basket for the first few months is on the NHS list for this week. If you're borrowing a cot, it says to get a new mattress that fits snugly and is clean and waterproof (NHS). The AAP says the mattress should be "very firm and should not sag under your baby's weight," and fit snugly with no gap against the crib walls (AAP).
On bedding, the two countries differ. The NHS says no pillows or duvets, and suggests a baby sleeping bag or light blankets (NHS). The US Consumer Product Safety Commission says "Bare is Best": nothing but a fitted sheet, no pillows or blankets (CPSC). The newborn guide follows the US rule.
Try today
The mattress fit test
Time: 5 minutes · Safe sleep, every sleep in the guide
Push the mattress hard against one side of the crib, then look along the opposite edge. There should be no gap against the crib walls (AAP).
Press your palm into the middle. It should feel very firm and not sag (AAP).
If it's borrowed, or fails either check, put a new snug mattress on the list (NHS).
Take everything out except one fitted sheet (CPSC).
Make it work:Do this one together. A crib is the kind of job that's easy to hand to the partner with the free Saturday.
Watch for
Normal
an occasional headache that clears with rest and water.
Call your provider
right away for a headache that won't go away or gets worse over time, even with medicine and fluids (CDC).
Normal
tired, achy legs after a day on your feet.
Call your provider
right away for severe swelling, redness, or pain in one leg or arm (CDC).
Normal
feeling hot, which the NHS lists among late-pregnancy symptoms (NHS).
For you
Sources
- NHS. "Week 31." Week-by-week guide to pregnancy, Best Start in Life. https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/3rd-trimester/week-31/
- American Academy of Pediatrics. "Choosing a Crib." HealthyChildren.org. https://www.healthychildren.org/English/ages-stages/prenatal/decisions-to-make/Pages/Choosing-a-Crib.aspx
- U.S. Consumer Product Safety Commission. "Safe Sleep – Cribs and Infant Products." CPSC. https://www.cpsc.gov/Safety-Education/Safety-Education-Centers/cribs
- Centers for Disease Control and Prevention. "Urgent Maternal Warning Signs and Symptoms." HEAR HER campaign, 2024. https://www.cdc.gov/hearher/maternal-warning-signs/index.html
- NHS. "Week 36." Week-by-week guide to pregnancy, Best Start in Life. https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/3rd-trimester/week-36/
- Office on Women's Health. "Pregnancy complications." U.S. Department of Health and Human Services. https://womenshealth.gov/pregnancy/youre-pregnant-now-what/pregnancy-complications
This guide is general education that summarizes published research and guidance from groups like the American Academy of Pediatrics, the CDC, and the WHO. It isn’t medical advice, and every child develops on their own timeline. Your pediatrician knows your child; if something feels wrong, call them. In an emergency, call 911.
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