Your precious baby is growing quite fast as you reach the halfway mark in your pregnancy and is approximately 5 3/4 – 6 1/2 inches in length now, measuring from crown to rump. If your baby were stretched out and measured from the top of the head to tip of the toes, he or she would be exactly half the size you can expect at birth. Your little one weighs almost 10 ounces, which is a major increase in weight since starting out as a single dividing cell, only 18 weeks ago. Your baby’s growth is taking up increasing space in the womb, but the growth rate will slow down a bit over the next few weeks.
Your baby’s heartbeat is stronger now and much easier to detect. Your doctor or midwife shouldn’t have any trouble picking it up at every prenatal visit. His or her heartbeat is normally about twice as fast as yours, anywhere from 120- 170 beats per minute (BPM). Up until now, your baby’s heartbeat may have been somewhere between 145-160 beats per minute, on average. As your baby’s heart develops, it may drop down a little to 130- 140. Your little one’s heart rate will likely change every time you have a visit with your doctor or midwife, depending on how far along you are, as well as whether or not your baby is active or is sleeping.
Some people believe that you can guess your baby’s gender by the heart rate; that girl’s heartbeats are faster than boy’s. This is based on the fact that women have a slightly higher pulse rate (because of a slightly higher metabolic rate) than men, but the truth is there is no correlation what-so-ever between the heartbeat of a baby in the womb and gender. This is just simply an old wive’s tale and therefore the heart rate is not a good predictor of gender. If you hear your baby’s heartbeat racing during your next visit (and are unsure whether you’re having a girl or a boy), don’t run out and buy pink paint for the nursery!
Your baby’s sensory development (sense of smell, taste, sight, hearing and touch) are becoming more specialized as each and every week goes by. The nervous system is still under development and your baby’s movements are a bit jerky and somewhat erratic. When you begin noticing movement, your little one may seem hyperactive because his or her muscles are becoming stronger. Trying these muscles out is fun! Flexing muscles and moving around inside the womb is still easy for your baby, since he or she isn’t too cramped yet.
You may think that your blood and your baby’s blood mix and exchange, but in actuality (under normal circumstances), it doesn’t mix at all. Your blood doesn’t flow directly into your baby and your baby’s blood never enters your bloodstream. If fetal blood and maternal blood did mix together, the mother’s body would soon make antibodies to the baby’s blood, which would lead to a miscarriage. One of the many tasks the placenta does is filter. It filters some substances (although many harmful toxins pass through, however) and keeps your blood and your baby’s blood separate. Your baby has a completely separate circulation, which is pumped by the heart at approximately 25 quarts a day, at this point in development.