# Day 117: Secondhand smoke

> Sixteen weeks and five days. Today is about the air around you: where smoke gets in, what it does, and one plan for each place.

- Series: Your fourth month of pregnancy, day by day (https://chorevia.com/learn/pregnancy-month-4), day 117 of 280, 16 weeks + 5 days
- Your baby this week: about the size of an avocado; around 11.6 cm from head to bottom
- Canonical URL: https://chorevia.com/learn/pregnancy-month-4/day-117
- Last reviewed: 2026-10-22
- Publisher: Chorevia (https://chorevia.com)
- Cite as: Chorevia. "Day 117: Secondhand smoke." Last reviewed October 22, 2026. https://chorevia.com/learn/pregnancy-month-4/day-117

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.

Sixteen weeks and five days. Today isn't about anything you do. It's about the air you breathe, and who else in your life shares it.

## Your baby

Around 11.6cm from head to bottom, about the size of an avocado ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)). The nervous system is still developing, and it's what lets the arms and legs move: the hands can form fists and may punch around inside the womb ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)).

## Your body

In the NHS, a routine carbon monoxide test is part of midwife appointments ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)). It's routine, not an accusation.

The CDC is plain about why it matters. Smoking in pregnancy slows fetal growth, so a baby may be too small even at full term; it roughly doubles the risk of abnormal bleeding during pregnancy and delivery, and it raises the risk of preterm delivery (birth before 37 weeks), stillbirth, cleft lip and cleft palate, and sudden infant death syndrome ([CDC](https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html)). Secondhand smoke counts on its own: breathing it during pregnancy can cause lower birth weight and may cause preterm delivery, and babies exposed to it face a higher risk of SIDS, ear and lung infections, and reduced lung function ([CDC](https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html)). "Stop smoking" sits on the NHS's to-do list for this week, next to giving up alcohol and cutting back on caffeine ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)).

## Try today

### The secondhand-smoke sweep

- **Time:** 10 minutes

1. List every place you breathe smoke in a normal week: the car, the porch, a relative's house, the break area at work.
2. Next to each, write one plan: smoking happens outside and away from you, the car stays smoke-free, you take a different seat at the family dinner.
3. Give the list to the people it names. The CDC's facts on secondhand smoke ([CDC](https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html)) do the arguing so you don't have to.
4. Keep the list where your partner can see it.

**Make it work:** You're not policing anyone's habit. You're asking for clean air for a few months, and most people say yes when the ask is specific.

## Watch for

- **Normal:** nosebleeds, which are on the NHS's list of common symptoms this week ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)). **Call your provider** about any bleeding from the vagina; the NHS says to seek advice for any bleeding ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)), and smoking roughly doubles the risk of abnormal bleeding in pregnancy ([CDC](https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html)).
- **Normal:** urine infections are common enough to be on the same list ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)). **Call your provider right away** for pain when urinating ([MedlinePlus](https://medlineplus.gov/ency/patientinstructions/000557.htm)).
- **Normal:** headaches ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)). **Call your provider** if headaches get worse or don't go away with rest and acetaminophen, because they can signal preeclampsia ([MedlinePlus](https://medlineplus.gov/ency/patientinstructions/000580.htm)).

## For you

If someone in your house smokes, this part is for them. The CDC says the best time to quit was before trying to get pregnant, the next best is as early in pregnancy as possible, and quitting at any point helps ([CDC](https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html)). That last clause is the one that matters now.

If you're the one who smokes, nothing here is a verdict. "Quitting smoking is important to have a healthy pregnancy and a healthy baby," the CDC says ([CDC](https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html)), and your midwife or doctor is the person to ask for help with it; the carbon monoxide test is there to help, not to catch you ([NHS](https://www.nhs.uk/best-start-in-life/pregnancy/week-by-week-guide-to-pregnancy/2nd-trimester/week-16/)).

If you're the partner and you don't smoke: your job is the list. Be the one who says "outside, please" at the barbecue, so she doesn't have to.

## Sources

- NHS. "Week 16." 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/2nd-trimester/week-16/
- Centers for Disease Control and Prevention. "Health Effects of Cigarettes: Reproductive Health." https://www.cdc.gov/tobacco/about/cigarettes-and-reproductive-health.html
- MedlinePlus. "Prenatal care in your second trimester." National Library of Medicine. https://medlineplus.gov/ency/patientinstructions/000557.htm
- MedlinePlus. "Aches and pains during pregnancy." National Library of Medicine. https://medlineplus.gov/ency/patientinstructions/000580.htm