Woman pregnant with twins having ultrasound

Twin Pregnancy Week by Week

March 15, 2019
9 min read

You’ve hit the jackpot — you’re having twins! Your little ones are busy growing and getting ready to meet you, and you’re also on an exciting (and maybe exhausting) journey toward the day you’ll take home your brood. Read on to discover how your twins are developing, and learn more about the pregnancy symptoms that might await you week by week.

What's in this article:

First Trimester: Your Pregnancy Symptoms and Your Twins’ Development 1-4 Weeks Pregnant With Twins 5-8 Weeks Pregnant With Twins 9-13 Weeks Pregnant With Twins Second Trimester: Your Pregnancy Symptoms and Your Twins’ Development 14-17 Weeks Pregnant With Twins 18-22 Weeks Pregnant With Twins 23-27 Weeks Pregnant With Twins Third Trimester: Your Pregnancy Symptoms and Your Twins’ Development 28-32 Weeks Pregnant With Twins 33-36 Weeks Pregnant With Twins 37-40 Weeks Pregnant With Twins Labor and Childbirth With Twins FAQs at a Glance

First Trimester: Your Pregnancy Symptoms and Your Twins’ Development

If you notice any early signs of pregnancy, a home pregnancy test might confirm that you're pregnant. But, only your healthcare provider can reveal that you’re pregnant with twins, often during an ultrasound scan at 12 weeks. If you’ve recently learned you’re having twins, read on, or check out our Twin Pregnancy Frequently Asked Questions for more information.

1-4 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Implantation bleeding. Light spotting can happen around when the fertilized eggs attach to the uterine lining, usually around two weeks after fertilization.
  • Breast tenderness. Hormonal changes can cause tender, swollen breasts, and this pain might be a little more intense when you’re carrying twins, thanks to the extra amount of the hormone hCG (human chorionic gonadotropin) your body is producing.

Baby Development

  • To start with, this is how twins form:
    • Fraternal twins. This is when two eggs are fertilized by two different sperm, creating two zygotes, each of which becomes an embryo. Fraternal twins will not be identical and can be either the same sex or a boy and a girl.
    • Identical twins. This is when only one egg is fertilized, and the zygote splits into two early in pregnancy, forming two embryos. Identical twins have the same chromosomes, and will look the same and be the same sex.
  • Implantation in the womb. At this stage, your twin babies are each a rapidly dividing ball of cells, and around two weeks after fertilization they burrow into the lining of the uterus. Read up on fetal development for more details.
  • Placentas begin to form. About three weeks after fertilization, a placenta will start to form for each baby. The placentas provide nourishment and oxygen to your twins. In some rare cases, the babies may share one placenta.
Types of twins

5-8 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Frequent urination. During pregnancy, the amount of blood in your body increases, and even more so when carrying twins versus just one baby. As your kidneys process this additional fluid, more fluid ends up in your bladder, meaning more bathroom runs than usual for you! Don’t drink less water, as staying hydrated is important, especially during pregnancy.
  • Fatigue. As your hCG and progesterone hormone levels increase, you might be more worn out than usual. Try to rest when you can.
  • Nausea and vomiting. It may be a little soon, but some moms-to-be start to experience morning sickness about a month after fertilization, and sometimes before. When you're pregnant with twins, morning sickness can be more severe than with a singleton pregnancy, but this is not always the case.

Baby Development

  • Brain and spinal cord start to form. Around six weeks, each baby’s spinal cord and brain start to develop from their own neural tube.
  • Little arms and legs sprout. By eight weeks of your twin pregnancy, your babies will have buds for limbs that look like little paddles.
  • Two heartbeats. Each baby's heart is beginning to form and may start to beat.
  • All major organs take shape. By the end of eight weeks, all your babies’ major organs, including the lungs and genitals, will have started to develop.

9-13 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Fuller breasts. Milk glands and fatty tissues in your breasts grow in preparation to feed not one but two babies! It might soon be time to shop for a larger, more comfortable bra.
  • Increased vaginal discharge. It’s a recurring theme, but a twin pregnancy means an increased level of blood and hormones coursing through your body. For this reason, you might also start to see more vaginal discharge. This is perfectly normal as long as it’s white or clear, and odorless. Contact your healthcare provider if you notice any itchy, burning, or bad-smelling discharge, as this could indicate an infection.

Baby Development

  • Fingers, toes, and nails appear. Your tiny duo will start to develop fingers, followed by little toes. By 12 weeks, fingernails will also begin to sprout.
  • Facial features debut. Around this time, your twins’ faces start to become less broad and more defined. Your babies will also have eyelids and a more developed profile, with the beginnings of a nose, eyes, and upper lip.
  • Tooth buds grow. Your babies’ future teeth are in place as tooth buds form under the gums.
  • Urine forms. Your little ones are starting to produce urine, which gets released into the amniotic sac.
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Second Trimester: Your Pregnancy Symptoms and Your Twins’ Development

Moms-to-be of twins usually show their bumps sooner, and the second trimester could be when other people suspect you’re having twins — if you haven’t revealed your news yet! Read on to find out what else is happening over the next few weeks.

14-17 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Weight gain. If your pre-pregnancy weight was normal, you might be advised to gain somewhere between 37 to 54 pounds over the course of your pregnancy. Experts recommend adding about 600 calories to your diet per day when you are carrying twins. To learn more, download our Pregnancy Weight Tracker and chat with your healthcare provider about an appropriate weight gain target that is right for your situation.
  • Lower back pain. As your uterus and belly expand, you might find your center of gravity shifts and your posture changes, placing strain your back. Talk to your provider about some safe stretches or exercises you can do to help ease the discomfort and strengthen your back muscles.

Baby Development

  • Boy or girl? Each baby’s sex organs will form around this time, but you might not find out the genders until 18 to 20 weeks, when an ultrasound might reveal it.
  • Eyes in motion. Although their eyes are still fused shut, at around 16 weeks your babies can slowly move their eyes behind the lids. Eyebrows and eyelashes have grown, too.
  • Tiny movements. Your babies' activity may be increasing and before long you'll be able to feel it.

18-22 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Difficulty sleeping. It might be increasingly hard to get a good night’s sleep, thanks to your growing belly. Sleeping on your side and using pillows to support your belly and as a cushion between your knees can help.
  • Stretch marks and itchy skin. As your skin stretches and as hormonal changes weaken the elastic tissue underneath your skin, stretch marks can appear and your skin might become itchy. Although stretch marks aren’t preventable, keeping your skin hydrated by drinking plenty of water and using a gentle moisturizer can help relieve some of the itchiness.
  • Dizziness. The increased blood volume during pregnancy can prompt some changes in your circulation that leave you feeling lightheaded. Try to move slowly, and lie down on your side when dizziness strikes, if that's possible.
  • Quickening. If you haven’t already, you’ll soon start to feel your babies move for the first time, which is called quickening. Every pregnancy is unique, so be patient if you haven’t felt anything yet  it’ll come in time. If you’re concerned about when your babies will start to move, chat with your healthcare provider. Once you feel kicks, your provider may ask you to count those precious movements for a few minutes each day. Download our Fetal Movement Tracker to help you get started when the time comes.

Baby Development

  • Sucking. As the sucking reflex develops, your little ones might suck their thumb if a hand floats up to the mouth.
  • Hearing develops. By 18 weeks, your babies may begin to hear, and the ears will start to protrude at the side of the head as well.
  • Skin is coated. Your babies may start to acquire a greasy, waxy coating called vernix, which helps protect their skin from the amniotic fluid.
  • Fine body hair appears. Around this time, your babies will be covered with a fine, downy protective layer of hair called lanugo. This helps keep the vernix on the skin and helps protect your twins’ skin from the amniotic fluid.

23-27 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Hot flashes. Hot flashes during pregnancy are often the result of hormonal changes and a speedier metabolism, leading your body to generate more heat than usual. Keeping hydrated and wearing comfy clothes can help keep you cool.
  • High blood pressure. At each of your prenatal checkups, your blood pressure will be checked. Among other things, your provider will be on the lookout for a serious blood pressure disorder called preeclampsia, which is a bit more common in twin pregnancies than in single pregnancies. If you notice any symptoms like swelling in your hands and face, persistent headaches, changes in vision, or difficulty breathing, contact your provider right away.

Baby Development

  • Fingerprints take shape. Your babies will start to form ridges in their palms and the soles of their feet. These will become fingerprints and footprints.
  • Your babies can respond to sound. Your babies may begin to respond to loud or familiar sounds, such as your voice, by moving.
  • Lungs prepare for their first breath. At 26 weeks, your babies’ lungs are producing surfactant, a substance that helps the air sacs stay inflated. This is an important part of your twins’ development as it’s necessary for breathing.
  • Handy hands. By now, your twins may be able to make grasping motions.

Third Trimester: Your Pregnancy Symptoms and Your Twins’ Development

During the third trimester, you may be feeling more aches and pains, but the end is in sight. Hang in there and read on!

28-32 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Hip and pelvic pain. This pain will likely go away after your babies are born, but if you feel any numbness in your feet or legs, let your healthcare provider know right away.
  • Braxton Hicks contractions. You may start to feel contractions this trimester, but these do not necessarily mean you are going into labor! These tightenings could be what are known as Braxton Hicks or false labor contractions. Braxton Hicks contractions help prepare your body for the real deal but don’t open the cervix. Talk to your healthcare provider if you’re in any doubt about what you’re feeling. Keep in mind, Braxton Hicks contractions usually occur irregularly, can stop when you change positions, and usually do not increase in intensity like true labor contractions do.
  • Hemorrhoids. Extra blood flow to the pelvic region combined with the pressure of a larger uterus can result in hemorrhoids, which are painful veins around the rectum. Try to eat a high-fiber diet and take warm baths to help relieve any discomfort.

Baby Development

  • Eyes open. Your twins may be able to open and close their eyes at around 28 weeks, and sense changes in light. Much of their time will be spent in rapid eye movement (REM) sleep with the eyelids closed.
  • Lanugo sheds. At 32 weeks of your pregnancy, your twin babies may start to shed the fine hair that’s covered their body for several weeks now.
  • Brain development. Each baby’s brain can now control body temperature, so your twins are less reliant on the amniotic fluid for warmth.
  • Bones hardening. Your twins’ bones continue to harden, but their skulls are still soft. This will allow them to pass through the birth canal more easily if you have a vaginal delivery.

33-36 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Leg swelling or pain. Fluid retention might be causing swelling in your legs and feet. Try elevating your feet whenever you can. Sudden or severe swelling in your feet can also be a sign of preeclampsia, a potentially serious blood pressure disorder, so let your healthcare provider know if you have any concerns about swelling.
  • Fatigue. If you’re feeling extra tired, you've got the best excuse ever. Being pregnant with twins can be draining! If you can, nap during the day and do some light exercise to keep your energy levels up.
  • Deep vein thrombosis. Although it’s not the most common condition among moms-to-be carrying twins, this blood clot disorder can occur if you’ve been placed on bed rest by your doctor. If you notice swelling in one leg, accompanied by pain in the calf and redness and warmth around the calf area, let your healthcare provider know right away. Your provider can give you advice on how to minimize your risk of deep vein thrombosis.

Baby Development

  • Vital organs continue to develop. Each baby’s lungs are preparing to breathe outside the womb, and the circulatory and musculoskeletal systems are nearly completely developed.
  • Weight gain. Your babies will continue to put on fat and gain weight. Most twin babies are born smaller than singletons, weighing on average 5.1 pounds each.

37-40 Weeks Pregnant With Twins

Twin Pregnancy Symptoms and Conditions

  • Snoring. There’s no shame in your game if your partner lets you know that you’ve been snoring lately. There’s not much to say about this phenomenon other than that it’s possible your breathing changes toward the end of your pregnancy. You can try wearing nasal strips or using a humidifier at night.
  • Difficulty moving. Your size, especially with two babies, can make moving around challenging. Take things slowly and relax whenever you can.

Baby Development

  • Head-down position. Your twins may be getting into the optimal position for a vaginal delivery, which means both babies are head down. In some cases, only one twin is head down or both babies are feet first. Your healthcare provider will be checking their position and will know what to do no matter what position they’re in.
  • The development continues. Your babies’ vital organs are developed enough for life outside the womb, but some, like the brain, continue to grow for many years to come.
Third trimester twins in womb

Labor and Childbirth With Twins

Twin pregnancies are considered “high risk,” the most common risk being preterm birth, with more than 50 percent of twins born before 37 weeks. Your healthcare provider will be working on getting the best outcome for you and your baby. In some cases, your healthcare provider may recommend inducing labor before your due date to avoid complications.

With a twin pregnancy, there may be a higher chance of you needing a cesarean section, but if there are no complications and the baby positioned nearest to the cervix is in a head-down position, it can be possible to have a safe vaginal delivery. Your healthcare provider will assess the safest option for you. If you have a vaginal delivery, you can expect labor to last longer than it would with a single baby.

Keep in mind, if your twins arrive early, they might need a little extra time in the hospital before doctors say that they’re ready to go home.

FAQs at a Glance

When will I know if I’m having twins?

A heartbeat (or two!) can sometimes be heard during a vaginal ultrasound at around six weeks of pregnancy, but the presence of more than one baby may be determined with more accuracy during an ultrasound exam at around 12 weeks.

What kind of weight gain can I expect when I’m pregnant with twins?

If you were of normal weight before you became pregnant, your recommended weight gain may fall between 37 to 54 pounds. Check with your healthcare provider for more personalized info, as many factors can contribute to your weight gain.

Twins come with their share of challenges, but they’re definitely a treat. You could say it’s double the trouble but also double the fun! To learn more, check out one mom's advice on getting through the first few weeks at home with your twins There is no doubt that handling two newborns will be exhausting at times, but you’ll be amazed by how your heart will grow for these babies. You’ve got this!

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Cleverland Clinic: First Trimester

NICHD: What are the symptoms of preeclampsia, eclampsia, & HELLP syndrome?

Mayoclinic: What causes ankle swelling during pregnancy — and what can I do about it?

US National Library of Medicine: Physiological changes in pregnancy

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Mayoclinic: Fetal development: The 1st trimester

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Mayoclinic: Fetal development: The 3rd trimester

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Mayoclinic: Fetal presentation before birth

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