Watch our video guide to Week 17 of your pregnancy journey:
What's Happening in Week 17?
Your baby is now about 13cm long (crown to rump) and weighs approximately 140g — roughly the size of a turnip or an open hand. Growth is accelerating and your baby is looking more and more like a newborn each day.
Several exciting developments are happening this week:
- Skeleton: the soft cartilage framework is gradually hardening into bone, a process called ossification. This will continue throughout pregnancy and into childhood
- Fat stores: a special type of fat called brown fat is beginning to develop under the skin. This will help regulate your baby's body temperature after birth
- Swallowing and sucking reflexes: your baby is practising these essential survival skills, swallowing amniotic fluid regularly
- Fingerprints: the unique swirl patterns on your baby's fingertips are forming this week — no two sets are alike, even in identical twins
- Umbilical cord: growing stronger and thicker, efficiently delivering nutrients and oxygen
Perhaps most excitingly, your baby's hearing is developing. The tiny bones of the inner ear are among the first to fully ossify, and your baby may begin responding to loud sounds. By the end of this week, they can hear your heartbeat, your digestive system, and your voice.
Your Body This Week
Welcome to what many women call the "golden trimester." First trimester nausea has usually eased, energy levels are improving, and you may be starting to feel genuinely well for the first time in weeks.
Physical changes you may notice:
- Visible bump: your uterus is now roughly halfway between your pubic bone and navel, and many women are starting to show
- Linea nigra: a dark vertical line may appear running down the centre of your belly. This is caused by increased melanin production and will fade after birth
- Round ligament pain: sharp or stabbing pains on one or both sides of your lower abdomen, caused by the ligaments stretching as your uterus grows. This is normal but can be startling
- Nasal congestion: increased blood flow can cause swelling of the mucous membranes in your nose
- Increased appetite: with nausea subsiding, many women find their appetite returns with enthusiasm
Preparing for the Anatomy Scan
One of the most important milestones of pregnancy is approaching: the detailed anatomy scan, typically performed between 20 and 24 weeks. This comprehensive ultrasound examines your baby's anatomy in detail, checking:
- Head and brain structure
- Face, eyes, nose, and lips
- Heart — all four chambers and major vessels
- Spine — full length assessment
- Abdominal organs — stomach, kidneys, bladder
- Limbs — arms, legs, hands, and feet
- Placenta position and amniotic fluid levels
This is also the scan where you can find out your baby's sex, if you wish. At Ultrasound Ireland, we recommend starting to think about whether you'd like to know — it's one of the most exciting decisions of pregnancy.
Nutrition and Wellbeing
Your baby's bones are actively developing, so calcium is particularly important right now:
- The HSE suggests aiming for 3 servings of dairy daily (milk, cheese, yoghurt)
- If you're dairy-free, consider calcium-fortified plant milks, tofu, or a supplement
- Vitamin D (the HSE recommends 15mcg daily) helps your body absorb calcium effectively
- Iron remains important as your blood volume continues to increase — eat iron-rich foods at least twice daily
- Omega-3 fatty acids from oily fish (limit 2 portions per week), walnuts, or flaxseeds support your baby's brain development
This is also a good time to stay active. Prenatal yoga, swimming, and walking are all excellent choices that can help with back pain, sleep quality, and overall wellbeing.
Common Questions
"When will I feel my baby move?" First-time mothers typically feel movement (called "quickening") between 18 and 22 weeks. It often starts as a fluttering sensation, like butterflies or gas bubbles. If you've been pregnant before, you may notice it earlier — sometimes as early as week 16.
"Is round ligament pain normal?" Yes, completely. The sharp, jabbing pains are caused by ligaments stretching to support your growing uterus. Changing position slowly, supporting your bump when you cough or sneeze, and warm baths can help.
"Should I be worried about stretch marks?" Stretch marks are largely determined by genetics and how quickly your skin stretches. Keeping skin well-moisturised may help with comfort, but there's no proven way to prevent them entirely.
This article is for general information purposes only and is not intended as medical advice. Every pregnancy is different. Always consult your GP, midwife, or healthcare provider for guidance specific to your circumstances.
Track your baby's growth and prepare for the anatomy scan with a Growth Scan at Ultrasound Ireland. You can also find out baby's sex with our Gender Scan from 16 weeks.