17 weeks pregnant
Week 17 of pregnancy means 119 days since the last period began. Use the form to place your own dates, or read the example below.
How it works
Add 280 days to the first day of your last period to get the due date. To find the current week, count the days since that day and divide by 7. On this page the pregnancy is 119 days from the first day of the last period.
Worked example
Say the first day of the last period is 24 May. The due date is 280 days later, on 28 February. After 119 days the date is 20 September. 119 divided by 7 is 17. That is the start of week 17. The 161 days left run to the due date. This example uses a 365-day year.
Common questions
What if my cycle is not 28 days?
The 280 day rule assumes ovulation near day 14. If your cycle is much longer or shorter, your doctor may adjust the due date, often with an ultrasound. With a 35-day cycle some clinicians add 7 days, which would move 28 February to 7 March.
Does a leap year change the due date?
It can. A year with an extra day in February moves dates after that day by one. The calculator above uses the real calendar for your dates. The span from 24 May does not cross February. A leap year changes nothing for 28 February.
How many months is 17 weeks pregnant?
About 3.9 months. A pregnancy is 40 weeks, a little over 9 calendar months. Months are only a rough guide. At 17 weeks there are 161 days to the due date.
Which trimester is week 17?
Second trimester. The first trimester covers weeks 1 to 13, the second covers weeks 14 to 27 and the third runs from week 28 to the birth. Week 17 is week 4 of the second trimester.
Why do weeks start from the last period and not conception?
Most people know the date of their last period but not the day of conception. Counting from the last period gives everyone the same starting point. A pregnancy is about two weeks longer on paper than from conception. Counted from conception, this would be week 15, which is 105 days.