Week 15: Muscle Development
The fifteenth week is a time of active muscle development and strengthening movements.
Baby size: Apple (45-50 mm)
Baby development
Hard Bones and Breathing Practice
Your little one is actively preparing for life outside the womb. Their skeleton continues to harden, and this process, known as ossification, can already be seen on X‑ray images (though they are not taken without specific indications).
What’s happening this week:
- Skeleton: Bones are becoming increasingly strong, especially the bones of the legs and head.
- Proportions: The legs have finally become longer than the arms.
- Breathing movements: The baby is training respiratory muscles by inhaling and exhaling amniotic fluid.
- Eyes: Although the eyelids are still closed, the eyes can already react to bright light if it is shone on your belly.
Your fetus weighs about 70 grams and measures over 10 centimeters. It already looks like a fully formed little person.
Changes for mom
"Pregnancy Rhinitis" and Other Surprises
Your body continues to adapt to the growing needs of the baby. This can lead to some unusual, but generally harmless, symptoms.
What you may notice:
- Nasal congestion: You may feel constant nasal blockage without cold symptoms. This is “pregnancy rhinitis,” caused by swelling of the mucous membranes.
- Nosebleeds: Increased blood flow and swollen mucosa can sometimes cause minor nosebleeds.
- Leg cramps: Often disturb you at night. The cause may be a shift in micro‑element balance or pressure of the uterus on nerves.
- Forgetfulness: The so‑called “momnesia” or “pregnancy brain” is a real phenomenon linked to hormonal changes.
These and other symptoms are a normal part of pregnancy. To learn more, read our article "Pregnancy Symptoms".
Overview
Week 15: Are These the First Movements?
At the fifteenth week your pregnancy feels increasingly real, and you may sense the first faint hints of your baby’s movements! This sensation, known as "quickening", feels like a light tickle or bubbles inside.
Your fetus is now the size of a large apple or an orange. He/she is moving actively, although if this is your first pregnancy you might feel the pushes a little later, around weeks 18‑20.
For you this is a week of steady good well‑being and a growing belly. The energy of the second trimester allows you to stay active and enjoy this wonderful period.
The feeling of the first movements is an incredibly moving and personal moment that creates a special bond between you and your child. Don’t worry if you haven’t felt anything yet — you have many weeks ahead for that.
The second trimester continues to delight. To learn about other pleasant moments and challenges awaiting you, check out our overview of the second trimester.
Tips for mom
Time to Prepare for the Important Ultrasound
One of the most important examinations lies ahead — the second scheduled screening. It’s time to start preparing for it mentally and physically.
Ideas for this week:
- Learn about the anatomical ultrasound. It is performed between weeks 18 and 22. The doctor will carefully examine all of the baby’s organs. You may even find out the sex!
- Practice sleeping on your side. This is the best position for circulation. Use pregnancy pillows for extra comfort.
- Eat more calcium. The baby’s bones are growing rapidly, so focus on cheese, yogurt, leafy vegetables and nuts.
- Don’t ignore the dentist. Gum health is more important than ever, as hormones make them more vulnerable.
Prenatal examinations are an essential part of caring for the health of you and your baby. Read more in the article "Screenings During Pregnancy".
Tips for partner
From Dreams to Concrete Plans
This is a great time to start turning abstract dreams about the baby into concrete plans and actions.
What you can do together:
- Start researching big purchases. Strollers, car seats, cribs — studying models and reviews can take a lot of time. Begin now to avoid rushing later.
- Offer her a foot massage. Cramps and leg fatigue are common issues. Your massage will be the best remedy.
- Be patient with her forgetfulness. Help her by creating shared to‑do lists or phone reminders.
- Discuss whether you want to know the baby’s sex. This is an important joint decision to make before the next ultrasound.
Creating a list of essential items is an exciting process. Start it with our article about baby‑prep purchases.
Checklist
Your Action Plan for Week 15
We continue moving at a comfortable pace of the second trimester.
- ✅ Schedule the second planned screening (anatomical ultrasound).
- 🛌 Buy a pregnancy pillow for comfortable side sleeping.
- 🧀 Add more calcium‑rich foods to your diet.
- 🗣️ Discuss with your partner whether you will find out the baby’s sex.
- 🛒 Start reviewing stroller and car‑seat reviews.
- 📚 Learn more about upcoming examinations by reading the article "Analyses and Examinations".