• The second trimester marks the middle of your pregnancy and lasts from weeks 13-26.
• You can look forward to learning the baby's sex, feeling the fetus move, and reduced nausea.
• During the second trimester, the fetus will grow from the size of a peach to a head of lettuce.

The second trimester of pregnancy spans weeks 13-26 and usually marks a turning point for you and your baby. This trimester is often referred to as the "honeymoon period," because symptoms from the first trimester, like morning sickness, start to fade, says Sherry Ross, MD, an OB-GYN with her own private practice.

Related Article Module: When do pregnancy cravings start and which cravings are a red flag

In the second trimester, the baby grows rapidly and can hear sounds and voices from outside the womb, says Ross. Highlights during this period include finding out the sex of the baby (if you want to) and feeling the baby move.

Here's a breakdown of what you can expect in the second trimester.

13 to 14 weeks pregnant

• How big is the baby: Around 3.5 inches and 1.5 ounces, about the size of a peach.
• What's developing in the womb: The baby's blood, bones, and genitals.
• What are common symptoms: A common symptom around this time is an increased sex drive, due to the pregnancy hormones. And your belly and breasts will continue to grow, says Ross.
• What to look out for: At your next ultrasound, your healthcare provider may ask you if you want to know the sex of the baby. Ross says your healthcare provider will also conduct additional tests to look at your baby's anatomy and check for any developmental risks like Down's syndrome.

15 to 16 weeks pregnant

• How big is the baby: Around 4.75 inches and four ounces, roughly the size of an avocado.
• What's developing in the womb: The baby's facial expressions and hearing, so the baby can start to hear noises like your heartbeat.
• What are common symptoms: Symptoms like skin changes (melasma), nasal congestion, dizziness, leg cramps, headaches, and white vaginal discharge are common during this trimester, says Ross.
• What to look out for: You may start to feel your baby move from week 16 onwards. Initially, the movements will feel like a fluttering sensation, known as "quickening." You may not feel them every day at first so don't worry if it's not consistent.

17 to 18 weeks pregnant

• How big is the baby: Around five inches and eight ounces, about the size of a sweet potato.
• What's developing in the womb: The beginnings of eyebrows, eyelashes, and lines along the baby's hands.
• What are common symptoms: You may have stomach pain during the second trimester, due to constipation, gas, or growing pains. This may be normal or an indication of something more serious.
• What to look out for: "Vaginal bleeding, uterine cramping, leakage of clear or bloody fluid, or pelvic pressure could be troubling second-trimester complications," says Ross. She says frequent urination, increased discharge, lower back pain, headaches, and diarrhea are also symptoms that you should report to your healthcare provider.

19 to 20 weeks pregnant

• How big is the baby: Around six inches and 11 ounces, roughly the size of a cantaloupe.
• What's developing in the womb: A thick waxy coating that protects the baby.
• What are common symptoms: As your belly grows and the skin adjusts, it may cause some pigmentation that typically shows up as a dark line down the middle of your stomach. As the fetus grows it will put pressure on your stomach, lungs, kidneys, and bladder, which may cause a stretching sensation in your groin area which is known as round ligament pain. On the upside, your hair may look thicker, shinier, and shed less.
• What to look out for: Week 20 is the halfway-mark of your pregnancy. Your healthcare provider may conduct an ultrasound around this time. If this is your first pregnancy, you'll start feeling the baby's movements by this time.

21 to 22 weeks pregnant

• How big is the baby: Around 7.5 inches and one pound, approximately the size of a spaghetti squash.
• What's developing in the womb: The baby's taste buds and sense of touch, so the baby may start to experiment by sucking a thumb or stroking a limb.
• What are common symptoms: You may experience an increased appetite. You'll also likely see stretch marks on your belly, breasts, or thighs that appear red at first and then fade to a silvery-white. As your body starts to prepare for the baby's arrival, your breasts may start to leak colostrum, a nutritious fluid that your body produces before your milk comes in. Ross says you may also experience Braxton Hicks contractions, which are typically irregular and painless, almost like a squeezing sensation.
• What to look out for: Contact your healthcare provider if your contractions are frequent, intense, or painful, as that could indicate premature labor.

23 to 24 weeks pregnant

• How big is the baby: Around eight inches and 1.25 pounds, about the size of an ear of corn.
• What's developing in the womb: The lungs and vital organs have developed to the extent that with neonatal care the baby has a chance of surviving if you deliver early; however, there is a possibility of disability.
• What are common symptoms: As you get closer to delivery, factors like cramps, heartburn, anxiety, backaches, and needing to urinate can make it hard for you to sleep.
• What to look out for: The baby will typically get pretty active around this time, so you'll probably feel movements and occasionally even hiccups.

25 to 26 weeks pregnant

• How big is the baby: Around nine inches and two pounds, approximately the size of a head of lettuce.
• What's developing in the womb: The baby starts growing hair and may start responding to your touch or voice.
• What are common symptoms: Carrying the extra weight can cause back pain. You may feel bloated and have swelling in your face, hands, and feet, due to water retention. You may also leak a little urine when you sneeze or cough.
• What to look out for: Typically, between weeks 24 and 28, your healthcare provider will do a prenatal test to check for gestational diabetes, which is a form of diabetes that can occur during pregnancy and lead to complications.

Insider's takeaway

Related Article Module: How much weight you should gain during each trimester of pregnancy, according to doctors

As the baby grows rapidly in the second trimester, you'll start to experience symptoms like stretch marks, gas, and constipation.

But you'll also likely have a lot more energy than you did in the first trimester, which can be a good time for you and your partner to start baby-proofing the home, finalizing your birth plan, and joining prenatal classes.

"This is an important trimester to make sure you are gaining the appropriate amount of weight, exercising regularly, and getting adequate amounts of sleep," says Ross.

Pregnancy symptoms you can expect each trimester of your pregnancy and how to alleviate themYes, pregnancy can cause acne but there are safe ways to treat itYou can take probiotics when pregnant. Science-backed benefits are fewWhat is a doula and how to know if one is right for your pregnancy