Welcome to the Golden Period: Your Second Trimester Start Guide

The Second Trimester: What It Is and Why It Matters

When does the second trimester start? It begins at week 13 of pregnancy and runs through the end of week 27 — roughly months 4, 5, and 6.

Here's a quick overview:

Trimester	Weeks
First	Weeks 1–12
Second	Weeks 13–27
Third	Weeks 28–40

If you just hit week 13, you've officially crossed into the second trimester.

For many people, this shift brings real relief. The worst of the nausea often fades. Energy starts coming back. And the pregnancy begins to feel more real — your bump grows, you may start telling people, and soon you'll feel your baby move for the first time.

But this trimester also comes with new questions: What's happening to your baby? What tests do you need? What symptoms are normal? And what should you actually be doing right now?

This guide answers all of it — clearly, step by step.

When Does Second Trimester Start?

The short answer is simple: the second trimester starts at week 13.

Most medical sources define the second trimester as weeks 13 through 27, with the third trimester starting at week 28. You may occasionally see tiny wording differences online, but the practical takeaway stays the same: once you reach week 13, you're in trimester two.

Exactly when does second trimester start in weeks?

If you're searching when does second trimester start, the official answer is:

• It starts at 13 weeks pregnant

• It includes week 13, 14, 15... through 27

• It ends at 27 weeks and 6 days

• The third trimester begins at 28 weeks

That matters because pregnancy is dated by gestational age, not usually by the day of conception.

Does the second trimester end at week 27 or start of week 28?

Both phrases are describing the same cutoff.

• "Ends at week 27" means the second trimester lasts through the end of that week

• "Third trimester starts at week 28" means the next phase begins immediately after

So there is no mystery gap where pregnancy is trimester-less. That would be very inconvenient.

How pregnancy weeks are counted

Pregnancy is usually counted as 40 weeks from the first day of your last menstrual period (LMP), not from the day fertilization happened. Because of that:

• You are considered about 2 weeks pregnant before conception usually occurs

• Ovulation and conception often happen around week 2

• Your due date is estimated from LMP, then refined if needed by ultrasound

If your cycles are irregular or you conceived later than expected, an early ultrasound may adjust your dating. At Living Well, we provide free ultrasounds to help confirm how far along you are.

Trimester	Timeframe	What it usually feels like
First	Weeks 1-12	Nausea, fatigue, uncertainty
Second	Weeks 13-27	More energy, growing bump, movement
Third	Weeks 28-40	Bigger belly, more pressure, getting ready for birth

What Happens to Your Baby in the Second Trimester

The second trimester is a busy season for baby development. Your baby goes from tiny-but-clearly-human to active, stronger, and much more noticeable.

Baby milestones from weeks 13 to 16

Early in the second trimester, growth speeds up.

By around 16 weeks, many babies measure about 6 inches long and weigh around 3 to 4 ounces. During these weeks:

• Bones keep hardening

• Fingerprints begin forming

• The baby starts making more purposeful movements

• Thumb sucking may begin

• Most amniotic fluid is increasingly made from the baby's urine

• External sex may become easier to identify on ultrasound

This is also when the body systems built in the first trimester keep maturing. If you want a fuller look at this stage, see our guide to your baby's development in the second trimester.

Baby milestones from weeks 17 to 20

These weeks are exciting because many parents first feel movement now.

Common milestones include:

• Quickening, or first felt baby movement, often between 18 and 22 weeks

• Baby grows to roughly 8 to 10 inches

• Weight reaches about 10 ounces by around week 20

• Facial features become more defined

• Soft fine hair called lanugo develops

• Protective coating called vernix begins forming

• A heartbeat may be heard with a stethoscope in some cases

Those first flutters can feel like bubbles, butterflies, or a tiny fish doing gymnastics. If this is your first pregnancy, you may feel movement a little later than someone who has been pregnant before.

Baby milestones from weeks 21 to 27

In the second half of this trimester, baby becomes more active and responsive.

Key milestones include:

• Baby can begin hearing and reacting to outside sounds, including voices

• Brain activity becomes more complex

• Hiccups may happen, which can feel like rhythmic little taps

• Movement patterns get stronger and easier to recognize

• Lungs continue developing and begin producing early surfactant later in the trimester

• By the end of this stage, baby may weigh around 1 to 2 pounds

A mid-pregnancy anatomy scan usually happens during this period and checks growth, body structures, placenta location, and more. For a medical overview of fetal changes, see Scientific research on fetal development in the 2nd trimester.

What You Can Expect in Your Body and Mood

For many people, the second trimester feels easier than the first. Not perfect, just easier. There is a difference.

Common physical changes after the second trimester starts

Once week 13 arrives, you may notice:

• Less nausea

• More energy

• A growing bump

• Increased appetite

• Breast growth

• Round ligament pain

• Heartburn

• Constipation

• Back pain

• Leg cramps

• Swelling in feet or ankles

• Nosebleeds or stuffy nose

• Bleeding gums

• More vaginal discharge

• Varicose veins

• Hemorrhoids

• Stretch marks

• Darker skin changes like linea nigra or melasma

• Braxton Hicks contractions later in the trimester

Many of these happen because of hormones, increased blood volume, and your growing uterus.

A few common examples:

• Round ligament pain often feels like a sharp pull in the lower belly with movement

• Braxton Hicks usually feel like tightening that comes and goes, rather than regular strong contractions

• Melasma and linea nigra are caused by increased pigment and often fade after birth

• Bleeding gums can happen because pregnancy affects your blood vessels and gum tissue

Emotional changes in the second trimester

The physical shift is only part of the story. Emotionally, the second trimester can bring:

• Relief after the first trimester

• Excitement and stronger bonding

• Anxiety about labor, parenting, or finances

• Body image changes

• Relationship stress or closeness

• Vivid dreams or nightmares

• Occasional mood swings

Some emotional ups and downs are common, but persistent sadness, severe anxiety, panic, or losing interest in everyday life deserve attention. Mental health matters in pregnancy too.

How to manage common second-trimester discomforts

A few simple habits can help a lot:

• Drink plenty of water

• Eat fiber-rich foods for constipation

• Keep taking prenatal vitamins

• Wear a supportive bra

• Choose supportive, low-heeled shoes

• Stretch gently before bed to help leg cramps

• Walk or do other provider-approved exercise

• Sleep on your side instead of flat on your back

• Use sunscreen to help prevent darkening of melasma

• Rinse with salt water and use a soft toothbrush for sore gums

• Mention any burning with urination, unusual discharge, or itching to your provider

Pelvic floor exercises can also be useful now, not just after birth. For more on body changes, visit our second-trimester body changes guide.

Prenatal Visits, Tests, and Healthy Habits During the Second Trimester

Your second trimester is not just about waiting for your belly to look more official. It is also a key time for prenatal care.

Most people have prenatal visits about every 4 weeks during this trimester, unless they have a high-risk pregnancy or need closer follow-up.

At these visits, your provider may check:

• Blood pressure

• Weight

• Urine

• Baby's heartbeat

• Uterus growth or fundal height

• Symptoms or concerns

Prenatal appointments and screenings to schedule

Common second-trimester tests and screenings include:

• Anatomy ultrasound at about 18 to 22 weeks

• Glucose screening for gestational diabetes at about 24 to 28 weeks

• Blood work for anemia

• Genetic screening such as the quad screen if offered or chosen

• Amniocentesis in certain cases, often around 15 to 20 weeks

• Rh-related testing and possible RhoGAM if your blood type requires it

• Placenta location and amniotic fluid assessment during ultrasound

The anatomy scan is one of the biggest appointments of this trimester. It looks at major body systems and can often show the baby's sex if you want to know. For more technical details, see Scientific research on second-trimester ultrasound.

Lifestyle tips for a healthy second trimester

Second-trimester basics are not glamorous, but they work:

• Eat balanced meals with fruits, vegetables, whole grains, protein, dairy or calcium-rich alternatives, and healthy fats

• Continue prenatal vitamins with nutrients like folic acid, iron, iodine, and choline

• Many experts suggest around 340 extra calories per day in the second trimester

• Aim for about 150 minutes of moderate exercise per week

• Good options often include walking, swimming, and prenatal yoga

Vaccines and prevention matter too:

• Flu vaccine is recommended during pregnancy when in season

• COVID-19 vaccination is considered safe in pregnancy

• Tdap is typically given later, usually in the early third trimester

Food and safety reminders:

• Avoid alcohol, smoking, and recreational drugs

• Limit caffeine

• Avoid raw or undercooked meat

• Avoid unpasteurized dairy

• Choose low-mercury fish

• Skip hot tubs and saunas

• Have someone else clean the litter box if possible

• Keep up with dental care

Second-trimester do's and don'ts:

Do:

• Take prenatal vitamins daily

• Go to all prenatal visits

• Stay active

• Eat regularly

• Hydrate

• Rest when tired

• Ask questions

Don't:

• Ignore severe symptoms

• Smoke or vape nicotine

• Drink alcohol

• Use drugs not approved by your provider

• Eat risky foods

• Overheat in hot tubs or saunas

When does second trimester start to feel easier?

For many people, relief starts sometime after week 13, especially as nausea and extreme fatigue ease. But not everyone gets a dramatic energy comeback montage.

Some people still have nausea, fatigue, or anxiety in the second trimester. Others develop new issues like heartburn or back pain. If you have a high-risk pregnancy, twins, or ongoing symptoms, the second trimester may not feel especially easy, and that's okay.

What to Prepare for Before the Third Trimester

This trimester is a smart time to make decisions before the third trimester gets more physically demanding.

Important decisions to make in the second trimester

Helpful things to work on now include:

• Start thinking about your birth plan

• Discuss delivery preferences with your provider

• Tour your birth hospital if available

• Sign up for childbirth or breastfeeding classes

• Choose a pediatrician

• Start a simple baby registry if needed

• Research childcare options

• Set up nursery basics

• Buy maternity clothes that are actually comfortable

• Talk with your partner or support person about roles after birth

You do not need a perfect nursery, a color-coded spreadsheet, and twelve swaddles organized by emotional tone. You do need a plan for support, feeding, transportation, and basic newborn care.

Work, leave, and insurance tasks to handle early

The second trimester is also a good time to handle paperwork before your brain gets too busy memorizing stroller features you never asked to know.

Consider:

• Telling your employer when you're ready

• Learning what leave options are available

• Looking into FMLA or workplace protections if applicable

• Starting maternity leave paperwork early

• Reviewing insurance coverage for birth and newborn care

• Planning your baby budget

• Remembering that newborn coverage often must be added within 31 days after birth

When to Call Your Provider in the Second Trimester

Some second-trimester symptoms are normal. Others need quick medical attention.

If something feels off, trust your instincts and call your provider.

Urgent symptoms that should never wait

Contact your provider right away or seek urgent care for:

• Vaginal bleeding

• Leaking fluid

• Severe cramping or severe abdominal pain

• Regular contractions before term

• Fever

• Severe headache

• Vision changes

• Sudden swelling in face or hands

• Shortness of breath

• Fainting

• Painful urination with fever or back pain

• Severe itching, especially with other symptoms

• Noticeably decreased movement later in the trimester after movement patterns are established

These can be warning signs of problems such as infection, preterm labor, or preeclampsia.

When symptoms are common but still worth mentioning

These may not be emergencies, but they are still worth bringing up:

• Burning with urination

• Odd-smelling, green, yellow, or itchy discharge

• Heartburn that is persistent or severe

• Swelling that is worsening

• Frequent Braxton Hicks that seem stronger or more regular

• Mood changes that feel heavy, scary, or hard to manage

For a broader overview, see Scientific research on what to expect in the 2nd trimester.

Frequently Asked Questions About When Does Second Trimester Start

When does second trimester start if I conceived later than my last period?

Pregnancy is still usually dated from your last menstrual period, so the second trimester generally starts at 13 weeks gestational age even if you ovulated later. If your dates seem off, an ultrasound can help confirm the timeline.

When will I feel the baby move after the second trimester starts?

Most people feel movement between 18 and 22 weeks. If this is your first pregnancy, it may happen later. If you have been pregnant before, you may recognize it sooner.

Is week 13 first trimester or second trimester?

Week 13 is considered the second trimester by most standard medical definitions. Some sources phrase trimester boundaries a little differently, but week 13 is the most widely used start point.

Conclusion

If you've been wondering when does second trimester start, the answer is clear: week 13. From there, the second trimester continues through week 27, with the third trimester beginning at week 28.

This stage often brings more energy, more visible growth, and some of the most memorable pregnancy milestones, from the anatomy scan to feeling those first flutters.

If you think you may be pregnant, need help figuring out how far along you are, or want support for an unplanned pregnancy, we're here for you. At Living Well, we provide free pregnancy tests, free ultrasounds, and compassionate support from licensed doctors, nurses, and ultrasound techs. Since 1985, we've been here for women in Orange, and in 2025 alone we served 1,420 local women.

You can learn more about your options and next steps here: pregnancy support from Living Well.

You do not have to figure it all out in one day. Just the next step is enough.