Enter your IUI date to get an estimated due date (EDD) and how far along the pregnancy is today (gestational age). The calculator assumes fertilisation happened around the IUI and adds 38 weeks. If you had an hCG trigger injection to time ovulation, that timing is already built in, because gestational age is counted from an assumed last menstrual period two weeks before the IUI.
What’s next?
Tip: First-trimester ultrasound usually gives the most precise dating.
Frequently asked questions
How is my IUI due date calculated?
We treat the IUI date as the day fertilisation likely happened and add 38 weeks (266 days) to estimate the due date (EDD). Gestational age is counted from an assumed last menstrual period two weeks before the IUI. So gestational age today is the days since IUI plus 14.
Does an hCG ovulation trigger change the result?
Not for the calculator math. The trigger simply times ovulation (typically 24–36 hours later) so your insemination matches release. Using the IUI date still yields the correct estimated EDD.
I had two IUIs on back-to-back days. Which date should I use?
Use the first IUI or your likely ovulation day; either choice is usually within a day. Your first-trimester ultrasound can refine dating.
Do twins change the due date?
The calculated EDD is the same, but actual delivery with multiples is often earlier. Follow your clinician’s plan for monitoring and timing.
Which method is most accurate?
Early ultrasound (usually in the first trimester) provides the most precise dating. LMP- or IUI-based dates are estimates.
Methodology and limits
What this estimates
In simple terms, the calculator pretends your period started 14 days before the IUI and counts pregnancy length from there. Obstetric dating counts gestational age from the last menstrual period (LMP). For intrauterine insemination (IUI), this tool sets a clinical LMP as the IUI date minus 14 days, then returns an estimated due date (EDD) as IUI plus 266 days (the same as LMP plus 280). This follows the approach in the American College of Obstetricians and Gynecologists Committee Opinion on due date calculation (ACOG Committee Opinion No. 700).
Trigger timing and IUI scheduling
Many IUI cycles use an hCG trigger to time ovulation, with insemination planned about 24 to 36 hours later. This coordination improves the chance that sperm are present near ovulation, but it does not change the dating formula above. An example comparison of 24 versus 36 hours after hCG is reported in
Fertility and Sterility.
Gestational age today
Gestational age is reported as the time elapsed since the clinical LMP, which is set as IUI minus 14 days. This mirrors the standard obstetric convention described in
ACOG’s due date guidance.
Timeline hints (typical)
These are common time points in many IUI programs and pregnancy care pathways:
- Home urine test: often most reliable on or after the first missed period, which is about 14 days after IUI when using this dating method. See, for example, Mayo Clinic information on home pregnancy tests.
- Serum beta hCG: many clinics schedule a blood test about 12 to 14 days after IUI. An example protocol is described in the University of South Florida IUI patient handbook (PDF).
- Early heartbeat scan: with high quality transvaginal ultrasound, a fetal heartbeat is often seen by about 6 weeks gestational age. See the Radiopaedia article on fetal heart beat.
- NIPT: non-invasive prenatal testing is commonly offered from 10 weeks gestational age onwards, as summarised in the ACOG prenatal genetic testing chart.
- Anatomy scan: many services schedule a detailed second-trimester ultrasound at 18 to 22 weeks, in line with ACOG guidance on ultrasound exams.
- Third trimester: many clinical guides define the start of the third trimester at 28 weeks of gestation, as illustrated in the NHS week-28 pregnancy guide.
Multiples note
The calculator always displays a single EDD. In practice, twins and higher-order pregnancies are often delivered before 40 weeks. Reviews and professional guidance suggest planned delivery for uncomplicated twins around 37 to 38 weeks, with earlier timing for some complications. Examples include an
AJOG MFM review on delivery timing in twins and the
ACOG Practice Bulletin on multifetal gestations.
Limitations and safety
These dates are based on population averages. Individual care teams may adjust dating with early ultrasound or other findings. This tool does not replace medical assessment. If you have heavy bleeding, severe pain, fainting, fever, or any urgent concern, seek medical care immediately.