Reaching the 31st week means you have now completed the first month of your third trimester and are entering the eighth month of your pregnancy. After the 30th week, your baby’s odds of surviving without any long-term complications are rising considerably every week . He would have around 95% chances of survival without any physical or mental anomalies if you were to give birth this week .
The fetal lungs continue to mature and are now capable of functioning on their own; however, they would need external medical assistance in case of preterm deliveries . The kidneys and urinary tract are mature, with your baby passing about 2 cups of urine every day. The amniotic fluid is replaced by your body several times a day to eliminate the fetal waste materials .
These final weeks are vital for the fetal brain development with trillions of neuron connections forming, enabling your baby to use all the five senses . Brain scans performed around week 31 shows separate sleep cycles, indicating that your baby might already be dreaming about you . At eight months of gestational age, babies might even be capable of sensing emotions in the mother and those around her by hearing their voices .
With the growing fat layer taking over the job of keeping your baby warm in the womb, he is now shedding the lanugo hair (the downy hair keeping your baby warm until now); but, you might notice traces of it on his back and shoulders at birth . The developing fat layer is also filling out his body, giving him a plumper appearance.
The last stage of gestation is also crucial for the immune system development, preparing your baby for the outside world. However, he would need your colostrum and breast milk to boost his immunity for fighting infections and diseases immediately after birth .
The 31st week is a milestone for reproductive development as this is the week when the testicles move into the scrotum through the groin. If you are having a girl, her clitoris has almost completed developing, awaiting to be covered by the still-growing vulva .
The relatively mature senses of vision and hearing, along with the developed neck and shoulder, allow your baby to turn his head in response to sound and light . He might even ‘jump’ (or make sudden jerky movements) in response to sudden loud noises or move rhythmically when you play some music he likes . Although his sense of smell is developed enough, he cannot smell anything yet as he is still submerged in fluid .
Your baby’s increasing size is gradually limiting the space inside the uterus so he might not be able to kick and punch as much as he was until last week . The wake and sleep periods of your baby might also become more defined by this stage . You might also notice a rhythmic movement lasting for a few minutes at a time – these are probably fetal hiccups.
In many cases, the baby settles in the birth position (head-down) by the 31st week; however, it is also normal for babies to be in a breech (feet-down) or transverse (lying sideways) position as there is still time for them to rotate into a proper position .
The baby is just over 16 inches (40 cm) long , as big as a pineapple or a bunch of leeks, weighing about 3.3 pounds (1.5 kg) . He has almost reached the newborn length (19 inches to 21 inches)  and will be gaining more weight (about 1.7 to 1.9 pounds ) than growing in length in these last few weeks .
The growth rate slows down a bit in twin pregnancies at this stage as the babies are now competing for nutrients to gain a healthy amount of weight before they are born  Although, they are as big as a baby in any singleton pregnancy at week 31.
The top of the uterus is now 4 inches above your bellybutton . You have probably gained around 3 to 4 pounds already in your third trimester, with the ideal range of weight gain being about a pound per week as your baby hits another growth spurt before birth .
You might notice your breasts leaking the thick, yellowish fluid colostrum as your body prepares for breastfeeding. However, it is completely normal if you do not have any such leakage. You will still be able to breastfeed your baby once he arrives .
31st week routine prenatal check up will include measuring your blood pressure to assess the risks of high BP and preeclampsia. Your doctor might also order a urine test to check for protein in the urine .
An ultrasound scan performed this week will show your baby moving his hands and feet and turning his head while also making different facial expressions. On a 3d ultrasound you can see your baby looking almost like how he is going to look at birth.
Published on August 28th 2014 by Pregmed Editorial Team.
Article was last reviewed on 8th September 2014.