Week 13 of pregnancy

Your baby this week

About 6.78 cm (crown-rump length; Source: INTERGROWTH-21st (Papageorghiou et al., 2014)) — about as long as a Santra (Mandarin orange) (Source: UF/IFAS EDIS CH079 'Sunburst Tangerine' (mandarin hybrid): fruit about 2½–3 in (6.35–7.62 cm) diameter). Every baby grows a little differently.

How your baby is developing

• Vocal cords are forming.UNSW Embryology (CC-BY)
• The intestines, which temporarily protruded into the umbilical cord earlier on, typically move into the abdomen this week — marking the end of the first trimester.UNSW Embryology (CC-BY)

How you may feel

• Entering the second trimester often brings more energy and less nausea for many people.ACOG
• Appetite commonly increases, and the bump may become more visible.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
• A severe or persistent headache that doesn't improve.ACOG
• Sudden swelling of the face, hands, or feet.ACOG
• Visual disturbances — blurring, flashing lights, or spots.ACOG
• Fluid leaking or gushing from the vagina (possible ruptured membranes).NHS
• Persistent pain in the upper abdomen, especially under the ribs on the right side.ACOG

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