Your baby-on-the-way is approximately 4 inches in length now or about the size of a pear, measuring from crown to rump. By the end of this week, your baby will weigh a little around 2.5 ounces. Taste buds have formed on your baby’s little tongue already and your baby’s digestive system is practicing moving food along in the intestines. Your baby’s pancreas is secreting insulin already now; at 15 weeks.
The bones in your baby’s body are becoming gradually harder and ossifying. Blood is beginning to form in your baby’s bone marrow, as his or her blood vessels continue forming; connecting to one another. Blood vessels are clearly visible underneath the surface of your baby’s transparent skin. Even though your little one won’t be able to make any noises until after birth, his or her vocal cords are developing inside the voice box and are forming the larynx.
Your baby’s external genitalia have been continuing to develop and mature. It’s becoming easier to determine male from female this week. Gender is nearing the point where it can be identified during an ultrasound by a very trained eye. But, keep in mind that ultrasounds are not 100% accurate and can be wrong, especially this early in pregnancy. Also around this time, boys prostate glands are developing and girls ovaries are descending from the abdomen into the pelvis. Your baby’s thyroid gland has matured, therefore hormone production is under way.
Since your baby’s diaphragm and central nervous system are developing and refining, it is not unusual for your little one to get a case of the hiccups now and then; beginning around this week. Occasional bouts of hiccups are completely normal and harmless to your baby. They rarely last long- usually not more than 5-15 minutes at a time. These hiccups are most likely caused from your baby drinking and breathing the amniotic fluid, which causes the diaphragm to contract. Your baby is too small for you to feel these little rhythmic and repetitive “bumps”. Soon you’ll notice them and be able to distinguish between kicks and hiccups. From this point on, if you have an ultrasound, you may very well catch your baby hiccupping on the screen. Sometimes hiccups can even be heard when your doctor or midwife is using a Doppler to listen to your baby’s heartbeat.