Week 12 of pregnancy

Your baby this week

About 5.56 cm (crown-rump length; Source: INTERGROWTH-21st (Papageorghiou et al., 2014)) — about as long as a Nimbu (Lime) (Source: UF/IFAS EDIS CH093 'Tahiti Lime': fruit 5.5–7 cm long, 4.7–6.3 cm diameter). Every baby grows a little differently.

How your baby is developing

• Reflexes are developing — the fetus can typically make sucking motions.UNSW Embryology (CC-BY)
• Nails are forming on fingers and toes, and the kidneys begin producing urine.UNSW Embryology (CC-BY)

How you may feel

• The risk of miscarriage typically decreases significantly by the end of this week.ACOG
• A small bump may start to become noticeable for some by the end of this trimester.NHS

Nutrition this week

• Folate (B9) — supports neural-tube closure — most critical in weeks 1–12 (Leafy greens)
• Iodine — fetal brain + thyroid development (Iodized salt)
• Vitamin B12 — with folate, for blood + nerves (Meat)

Tests & scans

• Nuchal-translucency + combined first-trimester screen (weeks 11–14)

When to reach out

• Heavy vaginal bleeding or passing clots.ACOG
• Severe or persistent abdominal or pelvic pain.ACOG
• Severe, persistent nausea or vomiting that prevents keeping any fluids down (possible hyperemesis gravidarum).NHS
• Fever of 38°C (100.4°F) or higher, or chills.WHO
• Severe dizziness, fainting, or a racing/irregular heartbeat.NHS
• Pain or burning when urinating (possible urinary tract infection).NHS

These apply to this week specifically. See the full list of urgent warning signs the CDC publishes for pregnancy and the year after birth.