Pregnancy Timeline
Key Milestones
Baby Size Week by Week
Trimester Guide: What to Expect
- Fatigue and increased need for sleep are extremely common
- Morning sickness (nausea/vomiting) peaks around weeks 8–10
- Baby's heart begins beating by week 6
- All major organs begin forming — neural tube closes by week 6
- First prenatal visit typically between weeks 6–8
- Risk of miscarriage drops significantly after week 12
- Baby is about 2.5 inches long by end of trimester
- Energy often returns — many call this the "honeymoon trimester"
- Baby bump becomes visible around weeks 16–20
- You may feel first movements (quickening) around weeks 16–22
- Anatomy scan ultrasound at week 20 checks organs and may reveal sex
- Baby can hear sounds by week 18 and responds to light by week 22
- Viability milestone reached around week 24
- Glucose screening test typically at weeks 24–28
- Baby gains about half a pound per week
- Braxton Hicks contractions (practice contractions) may begin
- Baby typically moves into head-down position by weeks 32–36
- Full term begins at week 37 — lungs are usually mature
- Prenatal visits increase to weekly starting around week 36
- Nesting instinct may kick in as due date approaches
- Most babies arrive between 39–41 weeks
This calculator provides estimates only and is not a substitute for professional medical advice. Due dates are approximations — only about 5% of babies are born on the exact estimated date. Always consult your healthcare provider for personalized prenatal care, accurate dating, and medical guidance throughout your pregnancy.
How Due Dates Are Calculated
A pregnancy due date (estimated date of delivery or EDD) is the approximate date your baby is expected to be born. While pregnancies average 40 weeks from the first day of the last menstrual period, the actual delivery date can vary by several weeks in either direction.
Naegele's Rule (Last Menstrual Period)
The most common method, Naegele's rule, adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day menstrual cycle with ovulation on day 14. If your cycle is longer or shorter than 28 days, the calculation adjusts by the difference. For example, a 30-day cycle adds 2 extra days to the due date.
Conception Date Method
If you know the exact date of conception (for example, if you were tracking ovulation), the due date is calculated by adding 266 days (38 weeks) from conception. Since gestational age is counted from the LMP (about 2 weeks before conception), this gives the same result as Naegele's rule for a standard 28-day cycle.
IVF Transfer Date
For IVF pregnancies, the due date is calculated precisely from the embryo transfer date. For a Day 3 embryo transfer, 263 days are added. For a Day 5 blastocyst transfer, 261 days are added. IVF dating is typically the most accurate since the exact fertilization and transfer dates are known.
Understanding Your Pregnancy Timeline
Pregnancy is divided into three trimesters, each with distinct developmental milestones and physical changes. Knowing your current week helps you understand what's happening with your baby's development and what symptoms to expect.
- First Trimester (Weeks 1–12): The fertilized egg implants, organs begin forming, and the heartbeat starts. Most pregnancy symptoms (nausea, fatigue) are strongest during this period.
- Second Trimester (Weeks 13–27): Rapid growth phase. The baby develops facial features, fingerprints, and can move and kick. Many women feel their best during this trimester.
- Third Trimester (Weeks 28–40): The baby gains weight, the lungs mature, and the body prepares for delivery. You'll notice increased fetal movement and Braxton Hicks contractions.
When Is My Baby Considered Full Term?
The American College of Obstetricians and Gynecologists (ACOG) defines term pregnancy as follows:
- Early term: 37 weeks 0 days through 38 weeks 6 days
- Full term: 39 weeks 0 days through 40 weeks 6 days
- Late term: 41 weeks 0 days through 41 weeks 6 days
- Post-term: 42 weeks 0 days and beyond