We’re getting down to the home stretch! The third trimester of pregnancy is about gaining weight and growing. Most of the
actual organ system development is complete, with the exception of the lungs, which continue to develop during this trimester.
The seventh month of pregnancy (weeks 27 to 30)
There is a considerable amount of fat, about 3% of body weight, under the skin now, which smooths out a lot of the wrinkles.
Space starts to get tight in the womb. As a result, the baby starts to move about less vigourously. To get comfortable, he
takes on a curled-up position in the uterus, with his arms and legs crossed.
During this period, the lungs are now capable of breathing air, and therefore, a baby born at this time has a reasonable chance
of surviving with intensive care. The central nervous system has matured to a point where it can direct the rhythmic breathing
movements and control body temperature.
At 28 weeks, the eyes reopen and the eyelashes develop. The liver and spleen are now important sites of blood cell production.
By 30 weeks, however, the bone marrow takes over the production of red blood cells. By 30 weeks in males, the testes begin
to move downward into the pouch of skin below the abdomen called the scrotum.
The eighth month of pregnancy (weeks 31 to 35)
During this period, weight gain chugs along at rapid speed. The baby gains 230 g (about half a pound) every week at this stage.
Usually by this stage, the baby has adopted a head-down position in the uterus, in which he will most likely stay until birth.
By the end of week 31, the organs are almost completely developed, apart from the lungs which are still not fully mature.
The baby may suck his thumb, hiccough, or cry. He has distinct sleep and wake habits. He can taste sweet or sour. The baby
responds to stimuli such as pain, light, and sound. The toenails are now visible, and the baby has quite a bit of soft downy
body hair called lanugo, and hair on his head.
Baby becomes very energetic this month and has periods of extreme activity. His movements will peak in week 32. You will be
able to feel him twist and turn. By week 33, the baby’s movements will become smaller because he will be too big to swoop
around in the womb anymore. He may hiccough from time to time, causing small rhythmic bumps in the uterus.
The baby’s heart rate is generally around 130 to 140 beats per minute. Although it has been suggested that the heart rate
may differ depending on whether the baby is a boy or girl, there is no evidence to prove this.
All of the organs are in place and most systems are well developed. The lungs, however, may still be immature. Babies born
at 34 weeks or later have a very good chance of survival.
The ninth month of pregnancy (weeks 36 to 40)
Baby becomes pretty plump this month. By full-term, fat makes up about 16% of the baby’s body weight. He now measures 50 cm
(20 inches) and weighs around 3400 g (7.5 lbs). More confined, and possibly engaged in the pelvis, the baby may feel less
active.
At this point, the baby's skin is pink and smooth, and the upper and lower limbs are chubby.
At 37 weeks, your baby has a firm grasp and shows a spontaneous orientation to light. The nervous system is now very mature.
There is little space to maneuver in the uterus now, and the baby moves less. There are only jabs from the feet and knees,
and movements of the baby’s head against the cervix.
During week 37, the fine hair called lanugo that covers your baby’s body begins to wear off. At full term, the skin is normally
bluish-pink. The chest is prominent. In males, the testes have descended into the scrotum. The intestines are filled with
meconium, which consists of cells shed from the lining of the gut; this will make up your baby’s first bowel movement after
birth. Although the head is smaller in relation to the rest of the body compared with earlier months, it is still quite large
and is a major consideration during birth. Your baby's immune system is still quite immature and will continue to develop
after birth.
Sometime this month, your baby’s head may begin to settle downward, deep inside the pelvis. This is called “lightening” because
there will be less pressure on your abdomen, and you will find it easier to breathe when this happens.
Kick counts
It is recommended that you keep track of your unborn baby’s kick counts from about six months of pregnancy, as a way of making
sure that she is OK. Each day, time how long it takes for your baby to make 10 kicks, flutters, swishes, or rolls. You should
feel at least 10 movements within two hours, but you will probably feel that many movements in a much shorter amount of time.
Use a notebook to record the time that you feel each kick, flutter, swish, or roll, until your baby has made 10 movements.
You may start to notice patterns and a general length of time that baby usually takes to make 10 movements. If you notice
major deviations from the pattern, check with your health care provider.
For more information, see "Kick Counts."
