Your baby this week

The tiny ball of cells usually settles into your uterus lining now. The placenta starts forming.

The hormone hCG starts rising this week. It's what a pregnancy test detects.

You this week

A pregnancy test might turn positive now, often close to your missed period.

Some people notice early tiredness, sore breasts, or mild cramping.

Week 4 of pregnancy

How your baby is developing

  • The blastocyst typically implants in the uterine lining around this week, and the placenta and amniotic sac begin forming.UNSW Embryology (CC-BY)
  • Pregnancy hormone (hCG) begins rising, which is what a home pregnancy test detects.ACOG

How you may feel

  • A home pregnancy test may turn positive around now, typically near the time of a missed period.ACOG
  • Some notice early fatigue, breast tenderness, or mild cramping.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)

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.

Part of the First trimester (weeks 1–13).

Educational reference only — not medical advice. Typical/average figures; every pregnancy differs. Always consult your doctor or midwife. Seek urgent care for any warning sign.

Tips for this stage

  • Warm milk is a good source of calcium; a pinch of turmeric (haldi) is a common Indian tradition, though there's no clinical evidence it adds a health benefit in this amountSource: NHS – Have a healthy diet in pregnancy (calcium from dairy)

Checklist

  • Confirm pregnancy with testSource: NHS Start4Life — Week 4 of pregnancy
  • Start folic acidSource: NHS – Vitamins, supplements and nutrition in pregnancy; CDC – Folic Acid
  • Choose an OB-GYN or antenatal care providerSource: NHS — Your antenatal appointments