Had an IUI procedure? Enter the date of your insemination to calculate your estimated due date, gestational age, and full pregnancy timeline.
What Is the IUI Due Date?
An IUI due date is the estimated delivery date after intrauterine insemination, calculated by adding 266 days to the IUI procedure date. Because IUI is scheduled within 12–36 hours of ovulation — either after a trigger shot or a natural LH surge — the procedure date stands in for the conception date.
That timing is what makes IUI dating unusually trustworthy. In a natural cycle, ovulation day is an estimate stitched together from period dates and cycle averages. In a monitored IUI cycle, ovulation was watched on ultrasound, nudged with medication, or both — so the starting line of the pregnancy is anchored to a real, documented event rather than an assumption.
The result feeds everything that follows: gestational age at each appointment, the window for first-trimester screening, and the anatomy scan schedule. Because IUI pregnancies begin with fertility treatment, most patients are already under close medical supervision, and having a precise, procedure-based due date helps that supervision stay on track from the very first blood test. If you are earlier in the journey and weighing your odds, our analysis of IUI success rates by age shows the per-cycle pregnancy rates for each age group.
IUI itself comes in a few flavors, and all of them date the same way. A natural or unmedicated IUI tracks your own cycle with ultrasound and LH tests, then performs the insemination around your natural surge. A medicated IUIadds oral medication like letrozole or Clomid — sometimes low-dose injectables — to encourage one or two strong follicles, with an hCG trigger shot to time ovulation precisely. Medicated cycles are more common because the timing is tighter, which is also what makes the resulting due date that much more reliable.
How to Use the IUI Due Date Calculator
- Find your IUI procedure date. Check your clinic portal, cycle paperwork, or appointment history for the day the insemination was performed.
- Use the successful cycle's date. If you have had more than one IUI cycle, enter the date of the cycle that led to this pregnancy — not an earlier one.
- Enter the date in the calculator above. Pick the month, day, and year of your IUI procedure.
- Read your result. You will see your estimated due date, current gestational age, and a complete timeline of milestones, baby development, and planning dates.
- Note your two-week wait math. Your beta test lands about 14 days after the date you entered; the calculator's timeline shows where that falls in gestational-age terms.
How the IUI Due Date Works
The 266-day count is the average length of a pregnancy measured from fertilization. IUI earns its place in this formula through its timing: the procedure is performed 24–36 hours after an hCG trigger shot, or within about a day of a detected LH surge, placing washed sperm in the uterus exactly when the egg is released or about to be. Fertilization then occurs within hours, so the IUI date and the true conception date are rarely more than a day apart.
This is also why IUI dating usually beats period-based dating for the same patient. The standard period method assumes ovulation on cycle day 14, but a monitored IUI cycle might have triggered on day 12 or day 18 — the clinic knows which, because it was watching the follicles grow on ultrasound. Using the documented procedure date carries that real information forward instead of replacing it with an average.
IUI vs IVF vs Period Dating: How Many Days to Add?
Every dating method counts to the same finish line — 40 weeks of gestational age — but they start from different events, so each adds a different number of days. The pattern is simple: the later the known event sits after the last period, the fewer days remain.
| Known date | Days to add | Why |
|---|
| First day of last period (LMP) | +280 days | Full 40 weeks, assuming ovulation on day 14 |
| IUI / insemination date | +266 days | Treated as the conception date — 38 weeks from fertilization |
| Ovulation / conception date | +266 days | Same anchor as IUI |
| IVF day-3 embryo transfer | +263 days | Embryo was already 3 days old at transfer |
| IVF day-5 embryo transfer | +261 days | Embryo was already 5 days old at transfer |
One vocabulary note that prevents a lot of confusion: gestational age is always 14 days more than fetal (post-conception) age. On the day of your IUI, the embryo does not exist yet — but you are already counted as 2 weeks 0 days pregnant. Every week number your clinic quotes follows that convention, and so does this calculator. If you conceived with a transfer instead, use the IVF due date calculator with the matching day count.
Worked Example: IUI Due Date
Suppose your IUI was performed on Tuesday, February 10, 2026, about 30 hours after your trigger shot. The calculation is February 10, 2026 + 266 days = Tuesday, November 3, 2026. That Tuesday is your estimated due date — 40 weeks of gestational age from the conventional 2-weeks-before-ovulation starting point.
Notice the weekday coincidence: adding exactly 38 weeks (266 days) always lands on the same day of the week as the procedure. If your period-based estimate said November 5, the two-day gap simply means you ovulated — and had your IUI — on cycle day 16 rather than the assumed day 14. The procedure-based date is the one to trust.
The two-week wait maps neatly onto gestational age as well. On IUI day you are considered 2 weeks pregnant by convention; the beta test at day 14 lands at 4 weeks; the first ultrasound showing a heartbeat at 6–7 weeks falls about a month after the procedure. Framing the wait this way helps: those 14 days are not empty time but the first two weeks of embryonic development, from fertilization through implantation.
Your IUI Pregnancy Timeline: Beta Test to Due Date
Because your start date is exact, every milestone of an IUI pregnancy can be mapped in advance — both in days post-IUI (dpiui) and in gestational age. Gestational age is always the dpiui count plus 14 days, which is why the beta test at 14 days post-IUI lands exactly at 4 weeks 0 days. Our guide on when to take a pregnancy test after IUI explains why that test date is set where it is, and what the early signs of pregnancy after IUI really mean before you get there.
| Milestone | Days after IUI | Gestational age |
|---|
| IUI procedure (counted as conception) | Day 0 | 2 weeks 0 days |
| Implantation window | Days 6–10 | 2 weeks 6 days – 3 weeks 3 days |
| Beta hCG blood test | Day 14 | 4 weeks 0 days |
| First ultrasound (gestational sac) | Days 21–28 | 5–6 weeks |
| Heartbeat usually visible | Days 28–35 | 6–7 weeks |
| NT / first-trimester screening window | Days 63–83 | 11 weeks – 13 weeks 6 days |
| End of first trimester | Day 83 | 13 weeks 6 days |
| Anatomy scan | Days 112–140 | 18–22 weeks |
| Glucose screening | Days 154–182 | 24–28 weeks |
| Full term begins | Day 245 | 37 weeks 0 days |
| Estimated due date | Day 266 | 40 weeks 0 days |
Only about 5% of babies arrive on their exact due date — the date is the center of a window, not an appointment. Most IUI pregnancies that reach term deliver within roughly two weeks on either side of it, and your clinic will refine the plan as scans accumulate.
Back-to-Back (Double) IUI: Which Date Counts?
Some clinics perform inseminations on two consecutive days to bracket ovulation — typically about 24 and 36 hours after the trigger shot. If that was your protocol, use the first IUI date in this calculator. Sperm from the first procedure can survive in the reproductive tract until the egg is released, and the two possible due dates differ by only 24 hours — a gap far smaller than the resolution of any dating ultrasound. If your clinic charted one of the two as the primary insemination, follow their date; otherwise the first date is the standard choice, and your 6–8 week scan will confirm it.
How Accurate Is the IUI Due Date?
IUI-based dating is a strong starting estimate — more reliable than period recall, though a notch below IVF, where the embryo's age is known exactly. The main uncertainty is small: ovulation can occur up to 36 hours before or after the procedure, so the true conception moment may sit a day or two on either side of the IUI date.
A first-trimester ultrasound at 6–8 weeks is the tiebreaker that settles any doubt, measuring the embryo's crown-rump length against known growth curves. Studies estimate these early scans date pregnancies within about 3–5 days of accuracy. In practice, most IUI patients find the procedure-based date and the ultrasound date agree closely, and the clinic then picks one official date for the chart.
There are formal rules for when the ultrasound actually overrides a known conception date. The American College of Obstetricians and Gynecologists (ACOG, Committee Opinion No. 700) advises redating only when first-trimester crown-rump length disagrees with the known date by more than 5 days up to 8 weeks 6 days, or more than 7 days between 9 weeks 0 days and 13 weeks 6 days. For assisted reproduction pregnancies, ACOG is explicit that the ART-derived date should be used and the ultrasound should not override it on small discrepancies — one more reason your IUI date carries unusual weight compared with period-based dating.
One more accuracy note specific to IUI: because the procedure is scheduled from ultrasound-measured follicle growth, the clinic usually knows your ovulation within about half a day — better than any at-home method short of IVF. The remaining uncertainty is biological, not informational: exactly when the sperm met the egg within that window, and exactly when implantation completed. Both vary by a day or two and are the reason even the best dating methods get confirmed by ultrasound.
For context, that level of agreement beats what period-based dating typically achieves for women with irregular cycles, where ovulation may fall a week or more from the assumed day 14. IUI patients rarely face that problem: the cycle was monitored, the follicles were measured, and the trigger — if one was used — pinned ovulation to a known 36-hour window. The procedure date is simply the most honest starting line you have.
When to Talk to Your Doctor About IUI Due Date
Call your clinic promptly for heavy bleeding (soaking a pad in an hour), severe pelvic pain, dizziness or fainting, or fever over 100.4°F. If your IUI cycle involved injectable fertility medications, also watch for ovarian hyperstimulation signs in the days after the procedure: rapid abdominal bloating, sudden weight gain, nausea, or shortness of breath. These are uncommon with the lower doses used for IUI, but they need same-day evaluation.
One-sided pelvic pain with light bleeding deserves a call too, since any pregnancy — including IUI pregnancies — carries a small ectopic risk until an ultrasound confirms the pregnancy is in the uterus. Later on, the standard red flags apply: regular contractions before 37 weeks, leaking fluid, decreased fetal movement, severe headache with vision changes, or any bleeding. Never hesitate to call; your team expects it.
A final note on progesterone support, which many IUI patients are prescribed after the procedure. It can cause breast tenderness, fatigue, bloating, and even light spotting — essentially a preview of early pregnancy symptoms. That overlap makes the two-week wait emotionally tricky, because every twinge feels meaningful. The symptoms prove the medication is in your system; only the beta test proves a pregnancy. If side effects feel severe or you are unsure whether to continue the medication, call your clinic rather than stopping on your own.
Follow your baby's progress with our pregnancy week-by-week guide, and if you are curious about multiples after fertility medication, try the twins chance calculator.
Sources and References
- American Society for Reproductive Medicine (ASRM). Intrauterine insemination (IUI) — patient fact sheet on how IUI is timed, performed, and followed up. reproductivefacts.org — Intrauterine Insemination (IUI)
- American College of Obstetricians and Gynecologists (ACOG). Methods for Estimating the Due Date. Committee Opinion No. 700, 2017 (reaffirmed since) — the standard for ultrasound redating thresholds and ART-derived due dates. acog.org — Committee Opinion No. 700
- American College of Obstetricians and Gynecologists (ACOG). Evaluating Infertility — patient FAQ covering ovulation induction and insemination treatment. acog.org — Evaluating Infertility FAQ
The +266-day method on this page is the standard conception-date convention used by fertility clinics: gestational age is counted from 14 days before the insemination, which is treated as the conception date. Last reviewed October 23, 2026.
This calculator provides estimates for educational purposes and is not medical advice. Always confirm with your healthcare provider.
