Your Baby at 40 Weeks

A Closer Look at Week 40

You made it to 40 weeks — your official due date! Your baby is now the size of a small pumpkin, weighing approximately 3.5 kilograms, with about 15% of their body weight composed of fat. This adipose tissue serves as essential insulation, keeping your baby warm during the transition from the perfectly regulated 37°C environment of the womb to the cooler, more variable temperatures of the outside world.

Your baby is curled up tightly inside the uterus with their knees drawn toward their chest, waiting for the hormonal signal that will initiate labour. This signal involves a complex cascade of hormones — including oxytocin, prostaglandins, and cortisol — originating from both your body and your baby's. Some researchers believe the baby's lungs play a triggering role, releasing a protein called surfactant protein A that signals the mother's immune system and helps initiate contractions.

It is worth noting that only about 5% of babies are actually born on their due date. The due date is an estimate based on a 40-week gestation from the first day of your last menstrual period, and healthy pregnancies commonly vary by two weeks in either direction. If you go past your due date, your healthcare provider will typically begin offering more frequent monitoring — including non-stress tests and amniotic fluid checks — to ensure both you and your baby remain healthy.

While waiting for labour to begin, stay active with gentle walks, which can help encourage your baby to descend further into the pelvis and may stimulate contractions. Rest when you can, eat well, and try to enjoy these final quiet moments before your family grows. The journey you have been on for the past nine months is about to reach its most extraordinary destination: meeting your baby face to face.