Imagine sitting in a bathtub for nine months; your skin would be a wrinkled mess. To prevent this, your baby's sebaceous glands are now producing a thick, white, waxy substance called vernix caseosa. It coats the entire body, waterproofing the fragile skin against the acidic amniotic fluid.
🍼 What's Happening With Your Baby
Now the size of a pomegranate, the baby's skeleton is continuing to ossify (harden) from rubbery cartilage into solid bone.
The umbilical cord is growing thicker and stronger to support the increasing demand for nutrients and oxygen.
Sweat glands are beginning to form, and the fetus is storing a specialized tissue called 'brown fat'. This brown fat is crucial—it will help the baby regulate its body temperature immediately after birth.
🤰 What You're Feeling This Week
Your appetite is likely robust, and you may notice your weight gain accelerating. This is normal and necessary; the baby is entering a massive growth spurt.
You might experience a sharp, shooting pain radiating from your buttocks down the back of your leg. This is sciatica, caused by the growing uterus compressing the sciatic nerve in your pelvis.
Increased vaginal discharge is still common, but you should also be alert to the signs of a urinary tract infection (UTI). UTIs are common in pregnancy due to the relaxed muscles in the urinary tract.
The Vernix Coating
The vernix caseosa is a brilliant biological innovation. Not only does it waterproof the skin, but it also contains antimicrobial proteins that protect the baby from infections and acts as a lubricant to help the baby slide through the birth canal.
✅ What To Do This Week
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Use a heating pad for sciatica — A warm heating pad on your lower back or buttocks (never on your belly) can help relieve the sharp, shooting pains of sciatica.
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Prepare for the Anatomy Scan — Your level 2 ultrasound (the big anatomy scan) is usually scheduled between weeks 18 and 22. Make sure it's on the calendar!
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Watch for UTI symptoms — If you feel burning during urination, have a sudden urge to urinate but pass very little, or notice foul-smelling urine, contact your doctor immediately. Untreated UTIs can lead to kidney infections and preterm labor.
"The weight of the pregnancy is becoming undeniable. The shift in your gravity, the ache in your hips—it is your body physically making room for a completely new life."
— A Note From Your Body, Week 17