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 gram
Baby this week
- •Blastocyst is implanting into the uterine lining
- •Cell division is rapidly accelerating
- •The amniotic sac is beginning to form
You this week
- •Missed period (though some spotting can occur during implantation)
- •Breast tenderness and swelling
- •Fatigue and increased need for sleep
- •Mild cramping (similar to period cramps)
- •Nausea may begin for some people
- •Heightened sense of smell
This week's tips
- •Take a pregnancy test if you've missed your period—home tests are most accurate from the first day of a missed period
- •Schedule a prenatal appointment with your healthcare provider to confirm pregnancy and discuss your health history
- •Start taking prenatal vitamins with folic acid if you haven't already (folic acid is crucial for baby's neural development)
- •Be gentle with yourself—this is still very early, and fatigue is completely normal
- •Avoid alcohol, smoking, and recreational drugs, and talk to your doctor about any medications you take
Informational only — always check with your doctor or midwife for advice specific to you and your baby.
Looking ahead
Next week, your baby will officially be considered an embryo, and their major organ systems will begin forming. You may also start noticing more pregnancy symptoms as hormones continue to shift.
Track your pregnancy on BringBaby
Join free to track your pregnancy week-by-week and find baby-friendly places to visit as baby grows.
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.
More free tools
Looking for places to bring baby?
Explore BringBaby