Week 12: Reflexes Develop
A milestone week! Your baby's reflexes are developing — if you poke your belly, baby might squirm in response. The risk of miscarriage drops significantly after this week.
Medically reviewed by Samantha L. Fox, RN, BSN, MSN
Nursing Informaticist · United States Navy Nurse Corps · Last reviewed
Your baby is the size of a...
🟢 Lime!
👶 Baby Development
- ✓Reflexes are developing — baby can open and close fists
- ✓Digestive system practicing contraction movements
- ✓Bone marrow is making white blood cells
- ✓Pituitary gland begins producing hormones
- ✓Vocal cords are forming
- ✓Intestines move into the abdominal cavity
💊 Common Symptoms
- •Morning sickness often improves this week
- •Increased appetite and energy
- •Darkening of the skin (melasma or linea nigra)
- •Dizziness when standing quickly
- •Less frequent urination (uterus rises out of pelvis)
- •Improved mood and energy
🩺Clinical Context — From a Nurse's View
Week 12 is the milestone many people wait for to share the news, and the data supports the timing — once you've passed 12 weeks with a documented heartbeat, the cumulative miscarriage risk is roughly 1-2%. The first trimester combined screen window closes at 13w6d, and the fetus is now reflexively moving (you can't feel it yet — that's another 6-8 weeks). The Doppler can usually pick up the heartbeat now; if your provider can't find it at this visit, that doesn't automatically mean a problem, especially if your placenta is anterior or you're carrying lower. They'll usually do an ultrasound to confirm. If you've made it this far without significant bleeding, your nausea is fading, and your bloodwork was unremarkable, you've cleared the highest-risk part of pregnancy. Now is a reasonable time to schedule the anatomy scan (typically 18-22 weeks) and to get the flu and Tdap (in third trimester) calendar set.
Written by Samantha L. Fox, RN, BSN, MSN — Emergency Department nurse, US Navy Nurse Corps officer.
🚨 When to Call (or Go to the ER)
- !Heavy bleeding — ER
- !Severe one-sided pain — ER
- !Persistent fever — call
- !Severe vomiting that hasn't improved — call about hyperemesis treatment
✅ Normal — Even If It Feels Worrying
- ✓Nausea fading over several days, not all at once
- ✓Energy returning
- ✓Linea nigra (dark line on belly) starting to appear
- ✓First belly stretches and slight bump visible
✅ To-Do This Week
- Many parents announce the pregnancy this week!
- Plan a creative pregnancy announcement
- Start a baby registry
- Get your teeth cleaned (dental health affects pregnancy)
- Consider telling your employer
- Celebrate — you've completed the first trimester!
🩺 Questions for Your Doctor
- ?What do the first trimester screening results show?
- ?Is the baby's growth on track?
- ?When is the next appointment?
- ?Should I be concerned about any genetic results?
- ?Can I resume more vigorous exercise now?
- ?Is it safe to get a flu shot during pregnancy?
📚 References
- [1]ACOG Practice Bulletin No. 200: Early Pregnancy Loss. Obstet Gynecol. 2018;132(5):e197-e207.
- [2]ACOG Committee Opinion No. 762: Prepregnancy Counseling. Obstet Gynecol. 2019;133(1):e78-e89.
- [3]ACOG Committee Opinion No. 718: Update on Immunization and Pregnancy: Tetanus, Diphtheria, and Pertussis Vaccination. Obstet Gynecol. 2017;130(3):e153-e157.
Editorial review: Samantha L. Fox, RN, BSN, MSN. Last reviewed: see footer.
Your baby is the size of a...