The short answer
17 weeks = 4 months
At 17 weeks pregnant, you are about 4 months pregnant — in month 4 of your pregnancy and in your second trimester.
Not sure of your week? Use the pregnancy week calculator to find it from your last period, due date or conception date.
The skeleton is changing from soft cartilage to bone, and the umbilical cord is growing stronger and thicker.
About the size of a pear
size comparison
13 cm
crown to rump (5.1 in)
140 g
average weight (4.9 oz)
A layer of fat is beginning to form under the skin, which will help with warmth and energy after birth. Sweat glands are developing, and the heartbeat is now regulated by the brain rather than beating spontaneously. The placenta is nearly as large as the fetus itself, dense with blood vessels.
Sizes and weights are averages — healthy babies vary widely, and your scan measurements are what count.
Increased appetite is common now that nausea has usually passed, and weight gain of around a pound a week is typical from here for many people. Feet may swell slightly by evening, and some notice they have gone up a shoe size. Sciatic-type pain down one leg can appear as the uterus presses on nerves.
Common symptoms this week
161
days to go
23
weeks to go
119
days so far
At 17 weeks 0 days you are 119 days into a 280-day pregnancy, which leaves 161 days — 23 weeks — until 40 weeks. That number drops by one for every day you move through this week. Remember 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: 21 days until the halfway point (20 weeks 0 days).
A calendar month averages about 4.3 weeks — not 4 — so you can't just divide your week number by four. Instead, months of pregnancy are counted as uneven buckets of 4 to 5 weeks, arranged so the full 40 weeks fits into 9 calendar months. Week 17 falls in month 4, in the second trimester.
Your care team will always use weeks and days rather than months, because screening windows and term definitions are set by exact week — months are just the everyday shorthand. For the full conversion, see the weeks to months chart, or go the other way with the months-to-weeks guide.
Your notes will show a week and a day — 17+3 or 17w3d, for example. Pick the exact day you are on for its own day count, countdown and month answer.
| Week + day | Shorthand | Days pregnant | Days to go |
|---|---|---|---|
| 17 weeks 0 days (this page) | 17+0 | 119 | 161 |
| 17 weeks 1 day | 17+1 | 120 | 160 |
| 17 weeks 2 days | 17+2 | 121 | 159 |
| 17 weeks 3 days | 17+3 | 122 | 158 |
| 17 weeks 4 days | 17+4 | 123 | 157 |
| 17 weeks 5 days | 17+5 | 124 | 156 |
| 17 weeks 6 days | 17+6 | 125 | 155 |
At 17 weeks pregnant, you are about 4 months pregnant — in month 4 of your pregnancy and in your second trimester. Months of pregnancy are counted as uneven 4–5 week buckets so that the full 40 weeks fits into 9 calendar months.
17 weeks 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.
About 23 weeks until the 40-week mark — though only about 1 in 20 babies arrives exactly on the due date. Most are born within two weeks on either side of it.
At 17 weeks 0 days you are 119 days into a 280-day pregnancy, so there are 161 days left until the 40-week mark — that's 23 weeks. The count drops by one for each day you move through week 17.
17 weeks is 119 days, counted from the first day of your last menstrual period (17 × 7 = 119). Add the days into your current week for the exact figure — for example 17 weeks 3 days is 122 days.