Week 18 of pregnancy

Your baby this week

About 222 g (estimated weight; Source: WHO fetal growth charts (Kiserud et al., PLoS Med 2017)) — about as heavy as a medium seb (apple, about 3 in across) (Source: USDA SR Legacy (FoodData Central) FDC 171688 'Apples, raw, with skin': portion '1 medium (3" dia)' = 182 g edible portion; SR28 FOOD_DES refuse 10% (Core and stem). As-purchased weight = 182 / (1 - 0.1) = 202.2 g.). Every baby grows a little differently.

How your baby is developing

• The ears have typically reached their final position, and the fetus may begin responding to sounds from outside the womb.UNSW Embryology (CC-BY)
• Yawning and hiccupping have been observed on ultrasound at this stage.UNSW Embryology (CC-BY)

How you may feel

• Many people feel the baby's first movements by now if they haven't already.ACOG
• Increased vaginal discharge and a shifting sense of balance as the bump grows are common.NHS

Nutrition this week

• Iron — blood volume rises ~50% — iron demand climbs (Red meat)
• Calcium — fetal skeleton mineralising (Dairy)
• Vitamin D — calcium absorption + bone (Fatty fish)

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.