Two months ago, your baby was simply a cluster of cells. Now he or she has functioning organs, nerves and muscles. Find out what happens during the second trimester by checking out this weekly calendar of events.
Week 13: Urine forms
Thirteen weeks into your pregnancy, or 11 weeks after conception, your baby’s intestines have moved from the umbilical cord to your baby’s abdomen. Your baby is also beginning to form urine and discharge it into the amniotic fluid.
Tissue that will become bone is also developing around your baby’s head and within his or her arms and legs. Tiny ribs may soon appear.
Week 14: Baby’s sex becomes apparent
Fourteen weeks into your pregnancy, or 12 weeks after conception, your baby’s arms have almost reached the length they’ll be at birth and your baby’s neck has become more defined. Red blood cells are forming in your baby’s spleen.
Your baby’s sex will become apparent this week or in the coming weeks.
By now your baby may be almost 3 1/2 inches (87 millimeters) long from crown to rump and weigh about 1 1/2 ounces (45 grams).
Week 15: Baby’s skeleton develops bones
Fifteen weeks into your pregnancy, or 13 weeks after conception, your baby is growing rapidly. Your baby’s skeleton is developing bones, which will become visible on ultrasound images in a few weeks. Your baby’s scalp hair pattern also is forming.
Week 16: Facial expressions are possible
Sixteen weeks into your pregnancy, or 14 weeks after conception, your baby’s eyes have begun to face forward and slowly move. The ears are close to reaching their final position. More-developed facial muscles may lead to various expressions, such as squinting and frowning. Your baby also can now make sucking motions with his or her mouth.
Although still too slight to be felt, your baby’s movements are becoming coordinated and can be seen during ultrasound exams.
By now your baby may be more than 4 1/2 inches (120 millimeters) long from crown to rump and weigh nearly 4 ounces (110 grams).
Week 17: Fat accumulates
Seventeen weeks into your pregnancy, or 15 weeks after conception, fat stores begin to develop under your baby’s skin. The fat will provide energy and help keep your baby warm after birth.
Week 18: Baby begins to hear
Eighteen weeks into your pregnancy, or 16 weeks after conception, your baby’s ears begin to stand out on the sides of his or her head. 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.
By now your baby may be 5 1/2 inches (140 millimeters) long from crown to rump and weigh 7 ounces (200 grams).
Week 19: Baby’s uterus forms
Nineteen weeks into your pregnancy, or 17 weeks after conception, 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.
For girls, the uterus and vagina may be forming this week.
Week 20: The halfway point
Halfway into your pregnancy, or 18 weeks after conception, your baby’s delicate skin is protected with a greasy, cheese-like coating called vernix caseosa.
You may be able to feel your baby’s first movements, also known as quickening.
By now your baby may be about 6 1/3 inches (160 millimeters) long from crown to rump and weigh more than 11 ounces (320 grams).
Week 21: Baby can swallow
Twenty-one weeks into your pregnancy, or 19 weeks after conception, your baby is about to gain more weight. By this week your baby is becoming more active and can swallow.
Week 22: Baby’s hair becomes visible
Twenty-two weeks into your pregnancy, or 20 weeks after conception, your baby is completely covered with a fine, down-like hair called lanugo. The lanugo helps hold the vernix caseosa on the skin. Your baby’s eyebrows may be visible.
By now your baby may be 7 1/2 inches (190 millimeters) long from crown to rump and weigh 1 pound (460 grams).
Week 23: Fingerprints and footprints form
Twenty-three weeks into your pregnancy, or 21 weeks after conception, your baby’s skin is wrinkled, more translucent than before and pink to red in color.
This week your baby begins to have rapid eye movements. Your baby’s tongue will soon develop taste buds. Fingerprints and footprints are forming. For boys, the testes are beginning to descend from the abdomen. For girls, the uterus and ovaries are in place — complete with a lifetime supply of eggs.
Week 24: Real hair grows
Twenty-four weeks into your pregnancy, or 22 weeks after conception, your baby is regularly sleeping and waking. Real hair is beginning to grow on his or her head.
By now your baby may be slightly longer than 8 inches (210 millimeters) from crown to rump and weigh more than 1 1/3 pounds (630 grams).
With intensive medical care, some babies born this week may be able to survive.
Week 25: Exploration continues
Twenty-five weeks into your pregnancy, or 23 weeks after conception, your baby’s hands are 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: Baby’s fingernails develop
Twenty-six weeks into your pregnancy, or 24 weeks after conception, your baby has fingernails.
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.
By now your baby may be 9 inches (230 millimeters) long from crown to rump and weigh nearly 2 pounds (820 grams).
Week 27: Second trimester ends
This week marks the end of the second trimester. At 27 weeks, or 25 weeks after conception, your baby’s lungs, liver and immune system are continuing to mature — and he or she has been growing like a weed. Your baby’s crown-to-rump length may have tripled since the 12-week mark.
The end of your pregnancy is near! By now, you may be tired of being pregnant — and eager to meet your baby face to face. But your uterus is still a busy place. Understand how fetal development continues as you approach your due date. Here’s a weekly calendar of events for the third trimester.
What to Expect
Second trimester pregnancy often brings a renewed sense of well-being. The worst of the nausea has usually passed, and your baby isn’t big enough to crowd your abdominal organs and make you uncomfortable. Yet dramatic pregnancy symptoms are on the horizon. Here’s what to expect.
During second trimester pregnancy, you may notice physical changes from head to toe.
- Larger breasts. Stimulated by estrogen and progesterone, the milk-producing glands inside your breasts get larger during second trimester pregnancy. Additional fat also may accumulate in your breasts. Although some of the initial breast tenderness may improve, nipple tenderness may continue throughout the pregnancy. A supportive bra is a must.
- Growing belly. As your uterus becomes heavier and expands to make room for the baby, your abdomen expands — sometimes rapidly. Expect to gain up to 4 pounds (nearly 2 kilograms) a month until the end of your pregnancy.
- Braxton Hicks contractions. Your uterus may start contracting to build strength for the big job ahead. You may feel these warm-ups, called Braxton Hicks contractions, in your lower abdomen and groin. They’re usually weak and come and go unpredictably. Contact your health care provider if the contractions become painful or regular. This may be a sign of preterm labor.
- Skin changes. As blood circulation to your skin increases, certain areas of your skin may become darker, such as the skin around your nipples, parts of your face and the line that runs from your navel to your pubic bone. Your skin may also become more sensitive to the sun. Use sunscreen.
- Stretch marks. You may notice pink, red or purple streaks along your abdomen, breasts, upper arms, buttocks or thighs during second trimester pregnancy. Your stretching skin may also be itchy. Moisturizers can help. Although stretch marks can’t be prevented, eventually they fade in intensity.
- Nasal and gum problems. As pregnancy increases your circulation, more blood flows through your body’s mucous membranes. This causes the lining of your nose and airway to swell, which can restrict airflow and lead to snoring, congestion and nosebleeds. Increased blood circulation can also soften your gums, which may cause minor bleeding when you brush or floss your teeth. Switching to a softer toothbrush may help decrease irritation.
- Your blood vessels dilate in response to pregnancy hormones. Until your blood volume expands to fill them, your blood pressure will fall and you may experience occasional dizziness. If you’re having trouble with dizziness, drink lots of fluids and rise slowly after lying or sitting down. When you feel dizzy, lie on your left side to restore your blood pressure.
- Leg cramps. Pressure from your uterus on the veins returning blood from your legs may cause leg cramps, especially at night. Stretch the affected muscle or walk your way through the cramps.
- Shortness of breath. Your lungs are processing more air than they did before your pregnancy. This allows your blood to carry more oxygen to your placenta and the baby — and may leave you breathing slightly faster and feeling short of breath.
- Vaginal discharge. You may notice a thin, white vaginal discharge. This acidic discharge is thought to help suppress the growth of potentially harmful bacteria or yeast. You might want to wear panty liners for comfort. Contact your health care provider if the discharge becomes strong smelling, green or yellowish or if it’s accompanied by redness, itching or irritation. This may indicate a vaginal infection.
- Bladder and kidney infections. Hormonal changes slow the flow of urine, and your expanding uterus may get in the way — both factors that increase the risk of bladder and kidney infections. Contact your health care provider if you need to urinate more often than usual, you notice a burning sensation when you urinate, or you have a fever, abdominal pain or backache. Left untreated, urinary infections increase the risk of preterm labour.