Pregnancy Calculator — Week 18: Baby Size, Symptoms & Due Date
You are in week 18 of a standard singleton pregnancy. Below is a complete evidence-based snapshot — baby's growth, your body, nutrition, exercise, red flags and a doctor visit checklist for this exact week.
Pregnancy Calculator
Enter the first day of your last menstrual period (LMP). EDD = LMP + 280 days.
Baby at week 18
This week: Ears reach final position on head. Uterus grows rapidly. Meconium accumulates in bowel.
Mother's body — what changes
In week 18 you may notice: 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.
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.
Doctor visit checklist — week 18
- ✓Anatomy ultrasound (18–22 weeks) — check all organs and placenta location
- ✓Blood pressure + weight + urine dipstick at every visit
- ✓Fetal heart tones from week 10–12 (Doppler)
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 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 ACOG, NHS UK and Mayo Clinic 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.
What is my EDD if today is week 18?
Your estimated due date is 22 weeks from today. Calculator adds (280 − 7 × 18) days to today's date.
Can I travel during week 18?
Second trimester (weeks 14–27) is the safest travel window. Wear compression stockings for flights over 4 hours.
Content aligned with ACOG, NHS UK and Mayo Clinic. 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.