|Inside your womb your baby is developing from what was a tiny single fertilized cell, dividing into 2, then 8, then 16 cells over a period of hours to days. By 5 weeks, you can see the baby’s heart beat and by 12 weeks ultrasound scanning can show a tiny but perfectly formed baby no larger than the length of your finger. At 20 weeks you can often feel movements, and from 24 weeks, a baby can live outside the womb. From 24 to 40 weeks the baby s growing rapidly, putting on weight and laying down fat, with baby’s lungs and organs developing.
- How baby grows
Baby develops from sperm and egg meeting, and then the embryo divides rapidly into many cells-each eventually forming a specific part of baby or placenta.
- The first six weeks
From this ball of cells, the embryo attaches to the wall of your womb, burrows in and grows rapidly so that by 6 weeks you can see the heartbeat and the ‘kidney bean’ shape of the fetus.
- Up to nine weeks
By 9 weeks, baby is about 3cm long and the major organs have developed, though you can only see the head and body on ultrasound scanning.
- Up to twelve weeks
The baby’s organs are largely developed, you can see the baby’s arms, legs, chest and profile.
- Up to sixteen weeks
Baby is now 12 cm from head to bottom, and the arms and legs seem to make purposeful movements.
- Up to twenty weeks
At 20 weeks your baby can respond to sound and vibration, and ultrasound scans can show baby’s face clearly.
- Up to twenty four weeks
By 24 weeks baby weighs over 600g, and all the organs are fully formed.
- Up to twenty nine weeks
Baby is making breathing movements and opening his eyes in the womb.
- Up to thirty five weeks
Nearly fully developed, the skin is still smooth and thin and baby’s lungs are nearly mature.
- By forty weeks
The average weight is now 3.5kg, and baby is fully mature-“full term” is considered as 37-42 weeks.
- Twins and multiple births
Twins and triplets develop in the same way as “singleton” babies, but are usually smaller and are born earlier.