The following pregnancy week by week guide of the second trimester briefly outlines all the changes happening to both mother and baby.
Week 13
As the second trimester of pregnancy begins, the placenta has developed and is providing the baby with oxygen and nutrients.
The baby's eyelids have fused together to protect the eyes. The baby will start to put his or her thumb in the mouth this week in preparation for sucking, which will develop further into the pregnancy.
Week 14
While most of the initial pregnancy symptoms experienced during the first few weeks have probably disappeared, other uncomfortable symptoms, such as constipation will arise.
Very fine hair will start appearing all over the baby's body. This hair is called 'lanugo', and should be shed just before the birth.
Week 15
At this point on the pregnancy week by week guide, it would be difficult to hide a pregnancy. Most women will be showing by now, therefore trading in their day-to-day clothing for maternity clothes.
The baby's skin is very thin and transparent, making it easy to see the blood vessels through it.
Week 16
An increase in blood production in the mother's body causes frequent nose and gum bleeding, and also causes more prominent veins on the face, neck and breasts.
The baby weighs almost 4 ounces this week, and is about 4.5 inches long from crown to rump.
Week 17
Breasts are undergoing considerable change. They are larger, more sensitive, and are starting to fill with breast milk. Because of this, it is possible that the breasts will already start to leak milk.
On this week, the baby weighs about 5 ounces and is about 5 inches long from crown to rump.
Week 18
Backaches are more likely to become a problem by this week. This is due to the centre of gravity shifting, and the added weight out front from the growing belly.
The baby's ears are moving to their final destination. Since the bones of the middle ear and the nerve endings from the brain are developing, the baby will be able to hear sounds, including the mother's voice.
Week 19
The baby's first movements may start to be felt by this week, which are referred to as 'quickening'. This may feel like butterflies in the stomach.
A white, cheesy substance called 'vernix caseosa' will now be covering the baby's skin, which protects the skin from chapping, since it is so delicate.
Week 20
An ultrasound will probably be done this week to ensure the normal development of the baby, and the fetal age. If desired, the sex of the baby can also be determined at this ultrasound.
The baby now weighs about 11 ounces and is about 6.3 inches long from crown to rump.
Week 21
The uterus is about 1/2 inch above the belly button. By now, a weight gain of about 10 to 15 pounds is considered healthy. In addition, the mother's feet and ankles will probably start to swell.
The baby's intestines have developed enough to be able to absorb fluid that is swallowed and passed through the digestive system to the large bowel.
Week 22
'Braxton Hicks' contractions will start some time around this week. These are painless contractions of the uterus, in preparation for labor and delivery.
The baby's senses are developing quite rapidly. He or she is starting to form taste buds, and can feel the uterus wall around him or her.
Week 23
Leg cramps, frequent urination and heartburn will get in the way of a good night's sleep. It is safer for the pregnant woman to lay on her side so that blood flow to the placenta is not restricted.
The baby weighs just over 1 pound by this week. The baby will consistently be moving the fingers, toes, arms, and legs, causing more noticeable movements from the mother's perspective.
Week 24
A glucose tolerance test will be conducted to detect of the mother has developed gestational diabetes, which is a temporary type of diabetes occurring in pregnancy causing problems in the newborn.
In preparation for breathing oxygen once the baby is born, the lungs are developing the ability to produce 'surfactant'. This is a substance that keeps the air sacs in the lungs from collapsing and sticking together when exhaling.
Week 25
Heartburn will continue to be a nuisance. This is caused by the relaxing of the valve at the entrance to the stomach so that it doesn’t close properly, which allows acid from the stomach to move upward into the esophagus.
The baby is about 9 inches long and weighs about 1.5 pounds. Capillaries are forming and filling with blood.
Week 26
Consuming an extra 300 calories per day is optimal to ensure proper nutrition for both mother and baby, and to ensure excess weight is not gained.
The baby weighs just about 2 pounds. The eyes soon open and start to blink.
Week 27
Shortness of breath continues to be a factor, even after the mildest activities. The uterus is close to the rib cage, making the lungs incapable of expanding fully.
The lungs, liver, and immune system of the baby still have further developing to undergo.
For more in-depth information, visit www.complete-pregnancy-guide.com.
References:
1. Curtis, Glade B., MD, OB/GYN, Your Pregnancy Week by Week, 1997
2. Eisenberg et al, What to Expect When You're Expecting, 1991
Lisa Simonelli Rennie - Lisa Simonelli Rennie is a stay-at-home mother of two young children who has years of writing experience. She has particular experience in ...
