IVF Pregnancy Calculator — Week 18 (Day 3 & Day 5 Transfer)
You are 18 weeks pregnant after IVF (gestational age counted from egg retrieval + 14 days for day-5 transfer, +12 days for day-3 transfer). Below is what your embryologist and REI clinic expect at this exact stage.
IVF Pregnancy Calculator
Enter your egg retrieval date and select day-3 or day-5 transfer. EDD = retrieval + 266 days.
Baby at week 18
At 18 weeks gestational after IVF transfer: Ears reach final position on head. Uterus grows rapidly. Meconium accumulates in bowel.
Mother's body — what changes
Post-IVF at week 18, clinical picture: Baby movements more consistent. Braxton-Hicks contractions may start (painless tightening).
Nutrition & supplements
Add ~340 kcal/day above pre-pregnancy baseline. Prioritise iron (27 mg/day), calcium (1000 mg), omega-3 DHA (200–300 mg) and 71 g protein. Continue prenatal vitamin. Post-IVF continue progesterone support and prenatal vitamin exactly as your REI prescribed. Do not add herbal supplements without clearance — many interact with luteal support.
Safe exercise
Continue 150 min/week. Avoid supine (flat-on-back) exercises after week 20 — they compress the vena cava. Swimming and prenatal Pilates are ideal now. After IVF avoid high-impact activity until confirmed viability at 8-week scan. Then follow standard trimester guidance.
Doctor visit checklist — week 18
- ✓Anatomy ultrasound (18–22 weeks) — check all organs and placenta location
- ✓Progesterone support review — continue until placenta takeover (week 10–12)
- ✓Beta-hCG doubling every 48–72 hours until viability scan
- ✓First IVF viability ultrasound at 6–7 weeks gestational
Warning signs — call your provider immediately
- ⚠Heavy bleeding (soaking a pad in an hour)
- ⚠Severe abdominal pain that does not ease
- ⚠Fever above 38°C / 100.4°F
- ⚠Sudden gush of fluid (early rupture of membranes)
- ⚠Absent fetal movement for 12+ hours after 24 weeks
- ⚠Severe headache + visual disturbance (preeclampsia)
Week 18 — Frequently asked questions
How accurate is the IVF Pregnancy Calculator at week 18?
The calculator uses standard gestational-age arithmetic (LMP + 280 days for standard; egg retrieval + 266 days for IVF day-5). Ultrasound crown-rump length between weeks 8–13 is more accurate (±5 days) than LMP — adjust EDD accordingly if the scan differs by more than 7 days.
What size is my baby at week 18?
Approximately the size of a bell pepper — length 14.2 cm and weight 190 g. These are median values from ASRM, SART and ESHRE references.
Which symptoms are normal in week 18?
Baby movements more consistent. Braxton-Hicks contractions may start (painless tightening). Every pregnancy is different — call your provider if anything on the warning-signs list appears.
Should I have an ultrasound at week 18?
Anatomy ultrasound (18–22 weeks) — check all organs and placenta location. Routine scan windows are: dating (10–13w), anatomy (18–22w), growth (28–32w).
How much weight should I gain by week 18?
Approximately 4.2 kg cumulative if you started at a normal BMI (IOM guideline). Underweight mothers gain more; overweight mothers less.
Day 3 vs Day 5 transfer at week 18 — what's the difference?
Day-5 blastocyst transfer adds 5 days to embryo age; Day-3 transfer adds 3 days. Gestational age = transfer date + (14 − transfer day) days + weeks since transfer. Both converge on the same due date; the difference matters only in the first 2 weeks.
Should I continue progesterone at week 18?
Most REI clinics wean progesterone by week 12. Follow your clinic's exact taper — abrupt stop before placental takeover risks miscarriage.
Content aligned with ASRM, SART and ESHRE. Reviewed by Dr. Maria Rehman, MD (OB/GYN). This page is educational and does not replace personal medical advice — call your obstetrician for any concern.