You are now well into your second trimester with the risks of early pregnancy complications considerably low, while your body is coming in better terms with being pregnant. You may already have started wearing maternity clothing as your baby continues to grow in size.
The backbone and the muscles in your baby’s back are gradually gaining strength, enabling him to straighten his head . The cartilaginous skeleton has already begun turning into bone, but the ossification process will finish only after birth so the bones remain flexible at the time of delivery .
At the same time, development of the facial muscles continues with your baby practicing swallowing, sucking  and making various facial expressions (however, he cannot control them at the moment).
Your baby can now move his eyes a little from side-to-side; however, the eyelids are still fused shut . The hearing also continues to develop with the growth of tiny bones in the baby’s ears, enabling him to hear your voice when you speak or sing . The skin remains transparent enough for you to see his developing blood vessels. Fat begins developing underneath the skin which will later act as insulation for the fetus .
The circulatory system, lungs and urinary tract are fully developed with your baby practicing to inhale and exhale the amniotic fluid that is protecting her within the amniotic sac . His body is now pumping around 25 qt. of blood every day , while the sweat glands are also growing in place .
The development of the umbilical cord is now complete with two arteries and a vein, protected by the jelly-like substance (Wharton’s jelly) covering the cord . The production of meconium, which will later be the first bowel movement of your baby after birth, also begins around this time in the fetal intestinal tract .
He is now almost as big as an avocado, being around 4.6 inches (11.68 cm) long, weighing 3.5 oz (100 gm) .
As you must already know, the baby has started to move his arms and legs by now. In most cases, the mother cannot feel these movements before the 20th week as the baby is still too small, nestled within the cushion provide by the placenta and amniotic fluid . However, you may start feeling a slight fluttering, often referred to as ‘quickening’  in your uterus around this week. Women having a placenta lying closer to the back of the uterus are more likely to feel these movements earlier than those with their placenta near the front uterine wall . Women carrying their second child generally recognize the fetal movements earlier than first time mothers .
This week, the uterus is located between your pubic bone and navel, with the fundal height (the distance between the top of the uterus and the top of your pubic bone) being around 16 cm .
So, the biggest change this week is the baby bump which is now large enough for others to notice. The round ligaments have already started to thicken and stretch to support the growing uterus. So, it is normal for you to feel occasional sharp pulls in your abdominal muscles and ligaments, especially when you make any sudden movements.
The production of colostrum, the first fluid produced by the breasts in preparation for breastfeeding, may start this week . Due to this, some women may notice their nipples leaking a thick yellowish fluid during the 16th-17th week.
An ultrasound scan performed this week will show your baby’s facial features to be more defined  with prominent nose, forehead, lips and the eyes close together in their proper place. The external genital organs are already developed; so, your sonographer might be able to detect the gender at this stage, depending on the position of the baby within the womb . Major physical defects can also be detected at this stage through ultrasound.
Your doctor will also use a Doppler device to check the fetal heartbeat and assess your baby’s health. According to old midwives’ tales, fetal heart rate over 140/min means you are having a girl while heart rate below 140/min indicates it is a boy. However, there is no scientific evidence for this theory .
Most of the early pregnancy signs are probably gone by now, but there is nothing to worry about if you still have a few lingering signs of morning sickness, dry mouth, insomnia and loss of appetite. These are likely to be more severe in twin pregnancies due to the comparatively higher estrogen and progesterone levels . Other common week 16 symptoms are:
Published on June 18th 2014 by Pregmed Editorial Team.
Article was last reviewed on 13th August 2014.