Also written 17+1 or 17w1d
The short answer
17 weeks 1 day = 4 months
At 17 weeks 1 day pregnant you are about 4 months pregnant — day 120 of your pregnancy, in month 4 and your second trimester.
Not sure of your exact week and day? The pregnancy week calculator works it out from your last period, due date or conception date.
160
days to go
22
whole weeks + 6d
43%
complete
You are 120 days into a 280-day pregnancy, so there are 160 days — 22 weeks and 6 days — left until you reach 40 weeks. Bear in mind that the due date is an estimate: only about 1 in 20 babies is born on it, and most arrive within two weeks on either side.
Next milestone: 20 days until the halfway point (20 weeks 0 days).
Months of pregnancy are counted in uneven buckets of 4 to 5 weeks, arranged so that the full 40 weeks fits into 9 calendar months. Week 17 sits inside month 4, and it stays there for all seven days of the week — so 17 weeks 0 days and 17 weeks 1 day are both "4 months pregnant".
If you want the strict calendar answer instead, divide by the real length of a month rather than by four: 120 days ÷ 30.4375 days per month = 3.9 calendar months. That figure drifts from the bucket-based month number, which is exactly why your care team sticks to weeks and days.
The days part matters clinically even when the month doesn't. Screening windows, term definitions and induction timing are all set by exact week and day — full term starts at 39 weeks 0 days, not "9 months". See the full weeks to months chart for every week.
The skeleton is changing from soft cartilage to bone, and the umbilical cord is growing stronger and thicker.
Read the full week 17 breakdown →
| Week + day | Months pregnant | Days pregnant | Days to go |
|---|---|---|---|
| 17 weeks | about 4 months | 119 | 161 |
| 17 weeks 1 day (you) | about 4 months | 120 | 160 |
| 17 weeks 2 days | about 4 months | 121 | 159 |
| 17 weeks 3 days | about 4 months | 122 | 158 |
| 17 weeks 4 days | about 4 months | 123 | 157 |
| 17 weeks 5 days | about 4 months | 124 | 156 |
| 17 weeks 6 days | about 4 months | 125 | 155 |
At 17 weeks 1 day pregnant you are about 4 months pregnant — day 120 of your pregnancy, in month 4 and your second trimester. Months of pregnancy are counted as uneven 4–5 week buckets so the full 40 weeks fits into 9 calendar months, which is why the extra 1 day doesn't change your month number.
"17+1" is the shorthand your midwife or doctor uses for 17 weeks 1 day — the number before the plus is completed weeks, the number after it is completed days into the current week. You may also see it written 17w1d. Both mean exactly the same thing.
17 weeks 1 day is 120 days, counted from the first day of your last menstrual period (17 × 7 = 119, plus 1). That leaves 160 days — 22 weeks and 6 days — until the 40-week mark.
About 22 weeks and 6 days until 40 weeks. Only about 1 in 20 babies arrives exactly on the estimated due date, though — most are born within two weeks on either side of it.
17 weeks 1 day is in the second trimester, which runs from 14 weeks 0 days through 27 weeks 6 days. The third trimester begins at 28 weeks 0 days.