Week 4 of Pregnancy
First trimester
For informational purposes only. This page is not medical advice. Every pregnancy is different — always consult your doctor, midwife, or healthcare provider for guidance specific to your situation. In an emergency, call your provider or 911 immediately.
Baby is
about the size of a poppy seed
0.1 inches · less than 1 oz
Baby this week
- •Implantation is complete or happening this week
- •Blastocyst is developing into an embryo
- •Cell differentiation beginning (forming three layers that will become all body systems)
- •Amniotic sac and yolk sac are forming
You this week
- •Missed period (most common sign you notice)
- •Mild cramping or spotting (can be normal during implantation)
- •Breast tenderness and tingling
- •Fatigue and increased need for sleep
- •Nausea may be starting (though often begins around week 6)
- •Heightened sense of smell
- •Mood changes due to hormonal shifts
This week's tips
- •Take a pregnancy test if you haven't already—they're most accurate from the first day of a missed period
- •Schedule your first prenatal appointment (usually around week 8-10, but calling now gets you on the books)
- •Start taking prenatal vitamins with folic acid if you haven't already
- •Avoid alcohol, smoking, and high-mercury fish
- •Be gentle with yourself—rest when you need to and don't worry if you're not feeling 'pregnant' yet
- •Track any symptoms in a journal if it helps you feel more connected or prepared for appointments
Informational only — always check with your doctor or midwife for advice specific to you and your baby.
Looking ahead
Over the next few weeks, your baby will grow rapidly and start developing a heartbeat (visible on ultrasound around week 6). Your body will continue adjusting to pregnancy hormones, and morning sickness may intensify.
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For informational purposes only. This page is not medical advice. Every pregnancy is different — always consult your doctor, midwife, or healthcare provider for guidance specific to your situation. In an emergency, call your provider or 911 immediately.
This content is for informational purposes only and is not medical advice. Every pregnancy and baby is different. Always consult your doctor, midwife, or pediatrician for guidance specific to your situation.
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