Pregnancy: Second Trimester

Information on what you can expect during the months 4-6 of your pregnancy.

Most women find the second trimester of pregnancy easier than the first. But it is just as important to stay informed about your pregnancy during these months. The following has been adapted from the National Women's Health Information Center website.

You might notice that symptoms like morning sickness and fatigue are going away. But other new, more noticeable changes to your body are now happening. Your abdomen will expand as you gain weight and the baby continues to grow. And before this trimester is over, you will feel your baby beginning to move!

Many of the aches and pains you had in the first trimester may continue. Some of the following aches and pains may make their first appearance during the second trimester:

Weight Gain

Everyone gains weight at different rates. On average, it is normal to gain about one pound per week, or about three to four pounds per month during this trimester.

Changes in Your Baby

By the end of the second trimester your baby will weigh about 1 3/4 pounds and be about 13 inches long. With this growth comes the development of fingers, toes, eyelashes, and eyebrows. Around the fifth month, you might feel your baby move! By the end of this trimester, all of your baby's essential organs like the heart, lungs, and kidneys are formed.

2nd Trimester Tests and Procedures

During the second trimester, you should continue to see your doctor for prenatal care.  Most pregnant women have monthly office visits with their doctor or midwife until the end of this trimester.

During the second trimester your doctor can use an ultrasound to see if your baby is developing in a healthy way and to find out your baby's sex. You will also be offered prenatal and screening tests to look for genetic birth defects.

Birth defects result from problems with a baby's genes, inherited factors that are passed down from the mother and the father at conception. Genetic birth defects sometimes occur in people with no family history of that disorder. Women over the age of 35 have the greatest chances of having a baby with birth defects.

Some of the diagnostic and screening tests your doctor might suggest in the second trimester include:

Amniocentesis

This test is performed in pregnancies of at least 16 weeks. It involves your doctor inserting a thin needle through your abdomen, into your uterus, and into the amniotic sac to take out a small amount of amniotic fluid for testing. The cells from the fluid are grown in a lab to look for problems with chromosomes. The fluid also can be tested for AFP. About 1 in 200 women have a miscarriage as a result of this test.

Chorionic villus sampling (CVS)

This test is performed between 10 and 12 weeks of pregnancy. The doctor inserts a needle through your abdomen or inserts a catheter through your cervix in order to reach the placenta. Your doctor then takes a sample of cells from the placenta. These cells are used in a lab to look for problems with chromosomes. This test cannot find out whether your baby has open neural tube defects. About 1 in 200 women have a miscarriage as a result of this test.

Maternal serum screening test

This blood test can be called by many different names including multiple marker screening test, triple test, quad screen, and others. This test is usually given between 15 and 20 weeks of pregnancy. It checks for birth defects such as Down syndrome, trisomy 18, or open neural tube defects.

Targeted ultrasound

The best time to get a targeted ultrasound is between 18 and 20 weeks of pregnancy. Most major problems with the way your baby is formed can be seen at this time. Some physical defects such as clubbed feet and heart defects may not be seen.

Your doctor can also use ultrasound to see if your baby has any neural tube defects, such as spina bifida. In most cases, if you want to find out the sex of your baby, you can ask your doctor during this test. This is not the most accurate test for Down syndrome.

While you are adjusting to the changes in your body, your baby is quickly maturing. Two months ago, your baby was simply a cluster of cells. Now, he or she has functioning organs, nerves and muscles. You may be amazed by how much your baby changes from week to week.

The following has been adapted  from  the Mayo Clinic website.

Week 13: Baby flexes and kicks

You can not feel it yet, but your baby can move in a jerky fashion by flexing the arms and kicking the legs. This week, your baby might even be able to put a thumb in his or her mouth.

Your baby's eyelids are fused together to protect his or her developing eyes. Tissue that will become bone is developing around your baby's head and within the arms and legs. Tiny ribs may soon appear.

Week 14: Hormones gear up

The effect of hormones becomes apparent this week. For boys, the prostate gland is developing. For girls, the ovaries move from the abdomen into the pelvis.

Meconium — which will become your baby's first bowel movement after birth — is made in your baby's intestinal tract. By the end of the week, the roof of your baby's mouth will be completely formed.

Week 15: Skin begins to form

Your baby's skin starts out nearly transparent. Eyebrows and scalp hair may make an appearance. For babies destined to have dark hair, the hair follicles will begin producing pigment.

The bone and marrow that make up your baby's skeletal system are continuing to develop this week. Your baby's eyes and ears now have a baby-like appearance, and the ears have almost reached their final position.

Week 16: Facial expressions are possible

Sixteen weeks into your pregnancy, your baby is between 4 and 5 inches long and weighs a bit less than 3 ounces. He or she can now make a fist.

Your baby's eyes are becoming sensitive to light. More developed facial muscles may lead to various expressions, such as squinting and frowning. Your baby may have frequent bouts of hiccups as well. For girls, millions of eggs are forming in the ovaries.

Week 17: Fat accumulates

Fat stores begin to develop under your baby's skin this week. The fat will provide energy and help keep your baby warm after birth.

Week 18: Baby begins to hear

As the nerve endings from your baby's brain "hook up" to the ears, your baby may hear your heart beating, your stomach rumbling or blood moving through the umbilical cord. He or she may even be startled by loud noises. Your baby can swallow this week, too.

Week 19: Lanugo covers baby's skin

Your baby's delicate skin is now protected with a pasty white coating called vernix. Under the vernix, a fine, down-like hair called lanugo covers your baby's body.

Your baby's kidneys are already producing urine. The urine is excreted into the amniotic sac, which surrounds and protects your baby.

As your baby's hearing continues to improve, he or she may pick up your voice in conversations — although it's probably hard to hear clearly through the amniotic fluid and protective paste covering your baby's ears.

Thanks to the millions of motor neurons developing in the brain, your baby can make reflexive muscle movements. If you haven't felt movement yet, you will soon.

Week 20: The halfway point

Halfway into your pregnancy, your baby is about 6 inches long and weighs about 9 ounces — a little over half a pound. You've probably begun to feel your baby's movements.

Under the protection of the vernix, your baby's skin is thickening and developing layers. Your baby now has thin eyebrows, hair on the scalp and well-developed limbs.

Week 21: Nourishment evolves

Although the placenta provides nearly all of your baby's nourishment, your baby will begin to absorb small amounts of sugar from swallowed amniotic fluid. This week, your baby's bone marrow starts making blood cells — a job done by the liver and spleen until this point.

Week 22: Taste buds develop

This week, your baby weighs in at about 1 pound.

Taste buds are starting to form on your baby's tongue, and your baby's brain and nerve endings can process the sensation of touch. Your baby may experiment by feeling his or her face or anything else within reach.

For boys, the testes begin to descend from the abdomen this week. For girls, the uterus and ovaries are in place — complete with a lifetime supply of eggs.

Week 23: Lungs prepare for life outside the womb

Your baby's lungs are beginning to produce surfactant, the substance that allows the air sacs in the lungs to inflate — and keeps them from collapsing and sticking together when they deflate. "Practice" breathing moves amniotic fluid in and out of your baby's lungs.

Your baby will begin to look more like a newborn as the skin becomes less transparent and fat production kicks into high gear.

With intensive medical care, some babies born at 23 weeks can survive. There are serious risks, however, such as bleeding in the brain and impaired vision. Advances in fetal medicine are steadily improving the odds for the tiniest preemies.

Week 24: Sense of balance develops

By now, your baby weighs about 1 1/2 pounds. Footprints and fingerprints are forming.

Thanks to a fully developed inner ear, which controls balance, your baby may have a sense of whether he or she is upside-down or right side up in the womb. You may notice a regular sleeping and waking cycle.

Babies born at 24 weeks have more than a 50 percent chance of survival. The odds get better with every passing week. Still, complications are frequent and serious.

Week 25: Exploration continues

Your baby's hands are now fully developed, although the nerve connections to the hands have a long way to go. Exploring the structures inside your uterus may become baby's prime entertainment.

Week 26: Eyes remain closed

Your baby weighs between 1 1/2 and 2 pounds. The eyebrows and eyelashes are well formed, and the hair on your baby's head is longer and more plentiful. Although your baby's eyes are fully developed, they may not open for another two weeks.

Week 27: Second trimester ends

This week marks the end of the second trimester. Your baby's lungs, liver and immune system are continuing to mature — and he or she has been growing like a weed. At 27 weeks, your baby's length will have tripled or even quadrupled from the 12-week mark.

If your baby is born this week, the chance of survival is at least 85 percent. However, serious complications are still possible.

Click on the highlighted links in this paragraph for more information about the 1st trimester and the 3rd trimester of your pregnancy.