Conception Calculator — Week 27 From Conception (Fetal Age)
You are 27 weeks from conception, which corresponds to 29 weeks of gestational age (LMP-based). This page focuses on true fetal age — how long the baby has actually been developing since fertilisation.
Conception Calculator
Enter your LMP. Fetal age = gestational age − 2 weeks.
Baby at week 27
At 27 weeks from conception (29w gestational): Regular sleep/wake cycles. Brain tissue and neurons develop rapidly. Lungs produce surfactant.
Mother's body — what changes
27 weeks post-conception, your body is: Third trimester begins. Breathlessness as diaphragm compresses. Fatigue returns.
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. Week 27 from conception (29 weeks gestational) needs targeted micronutrients — the developmental window differs from LMP-based advice.
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. At 27 weeks from conception, low-impact activity supports placental blood flow without stressing the fresh implantation.
Doctor visit checklist — week 27
- ✓Antenatal visits move to every 2 weeks
- ✓Note: 27 weeks from conception = 29 weeks LMP — clinic dating uses LMP
- ✓Confirm dating with crown-rump length at 8–13 weeks (±5 days accuracy)
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 27 — Frequently asked questions
How accurate is the Conception Calculator at week 27?
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 27?
Approximately the size of a cauliflower — length 36.6 cm and weight 875 g. These are median values from ACOG dating criteria and Mayo Clinic conception timeline references.
Which symptoms are normal in week 27?
Third trimester begins. Breathlessness as diaphragm compresses. Fatigue returns. Every pregnancy is different — call your provider if anything on the warning-signs list appears.
Should I have an ultrasound at week 27?
Antenatal visits move to every 2 weeks. Routine scan windows are: dating (10–13w), anatomy (18–22w), growth (28–32w).
How much weight should I gain by week 27?
Approximately 8.3 kg cumulative if you started at a normal BMI (IOM guideline). Underweight mothers gain more; overweight mothers less.
27 weeks from conception is how many weeks pregnant?
27 weeks from conception = 29 weeks gestational (LMP-based). All clinical care uses LMP dating unless IVF or dating scan overrides.
Can I feel conception happening at week 27?
No — conception itself is not felt. Later pregnancy symptoms are hormone-driven, not conception-related.
Content aligned with ACOG dating criteria and Mayo Clinic conception timeline. 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.