Twin Pregnancy Week by Week an Overview

Your ultrasound detected two heartbeats. You know what that means right? You’re having twins! Twin pregnancy is double the fun, double the love, and double the trouble. Being pregnant with twins is slightly different. Keep on reading to find more about your twin pregnancy symptoms, how your twins develop, and more. Also a breakdown of everything that you will experience from the time you find out, to when you’ll walk home with the newest members of your family.

First Trimester: Symptoms and Development

When you start to notice the first signs of pregnancy, an at-home pregnancy test can confirm if you are pregnant or not. But, only a medical professional can reveal that you are pregnant with twins. This is often detected in an ultrasound done at 12 weeks.

Twin Pregnancy: 1-4 weeks

Symptoms of the mother

Twin pregnancy symptoms at 4 weeks are very similar to the symptoms of a single pregnancy. In the first 4 weeks, an expecting mother may face ‘implantation bleeding’, this is when light spotting happens when the fertilized eggs attach to the uterine lining. The spotting may happen two weeks after fertilization. The other more common symptom is the swelling of the breasts. Hormonal changes while being pregnant lead to the tenderness and swelling of the breasts. The pain could be more intense when you are carrying twins. This happens due to a higher amount of the hCG hormone. hCG stands for ‘Human Chorionic Gonadotropin’, this hormone produced by a tissue that is found in early embryos. Measuring hCG helps in the detection of pregnancy in women.

Development of twins

Let’s start from the beginning and know how twins are formed.

Fraternal twins:

When two eggs are fertilized by two different sperms, they create two zygotes. Each zygote then becomes an embryo. Fraternal twins are not identical but can be of the same sex or a boy and girl.

Identical twins:

In the case of identical twins one egg is fertilized, and the zygote splits into two. These two zygotes form two embryos. As the name suggests, identical twins will look the same and will also be from the same sex. This is because identical twins have the same set of chromosomes.

Implantation in the womb:

In this stage of twin pregnancy, the twin babies are rapidly dividing the ball of cells. Around two weeks after they are fertilized, they burrow into the uterine lining.

Formation of placentas:

A placenta starts to form for each baby about three weeks after fertilization. The placentas help in nourishing your baby and providing oxygen to your twins. In rare cases, twins may also share the placenta.

Twin Pregnancy: 5-8 Weeks

Symptoms of the mother

Urination: When a woman is pregnant, the amount of blood in her body increases. The flow of blood then increases even more in twin pregnancy as compared to a single pregnancy. This results in your kidneys processing additional fluid, which means more fluid that ends up in your bladder. This translates to more bathroom runs than usual! This is a completely common symptom of pregnancy and there isn’t anything to be worried about. Make sure you consume enough water even if you have to pee frequently. Staying hydrated during pregnancy is very important.


Rise in the levels of hCG and progesterone can lead to fatigue. Whenever you feel more worn out than usual, take ample rest if possible.

Morning sickness:

Expecting mothers to start to experience a wave of nausea about a month into fertilization. In some cases, a mother may experience morning sickness even before that. It is a possibility as a symptom of twin pregnancy at 6 weeks, mom’s with twin pregnancy may feel severe morning sickness as compared to mom’s who have a singleton pregnancy.

Development of twins

  • The brain and the spinal cord start to form at around 6 weeks. Each baby’s brain and spinal cord start to develop from their respective neural tube.

  • Around eight weeks into your twin pregnancy, your twins will start sprouting limbs. They will have little arms and legs that look like little paddles.

  • The baby’s heart starts to form around your eight weeks of twin pregnancy. Your ultrasound will detect two heartbeats, one of each twin.

  • Between the fifth and eighth weeks, all the major organs in your twins will start to develop. By the end of eight weeks, your twins’ major organs, which include lungs and genitals start to develop.

Twin Pregnancy: 9-13 Weeks

Symptoms of the mother

- The milk glands and fatty tissues in your breasts will start to grow to prepare your body for breastfeeding. Your breasts will be larger than normal as your body is preparing to feed not just one, but two babies!

- There will be an increase in your vaginal discharge in twin pregnancy. The rise in the levels of blood and hormones leads to an increase in discharge. This is a normal phenomenon across all pregnancies. As long as the discharge is odorless, white, or clear there isn’t anything to be worried about. In case you notice any itchiness, burning, or foul-smelling discharge, contact your doctor. This is to make sure that there isn’t any chance of infection.

Development of twins

- Your duo of tiny tots will start developing fingers, toes, and nails. 12 weeks into twin pregnancy, fingernails will start to sprout.

- In this period of twin pregnancy, the facial features of your twins start to show. Their features become more defined and their face gets less broad. The babies will also start to have eyelids along with the beginnings of the nose, eyes, and upper lip.

- Tooth buds also start to develop. Tooth buds are under the gums from where your twins’ teeth will start to grow.

- There is a formation of urine between this period. The twins then release this urine into the amniotic sac.

Second Trimester: Symptoms and Development

Mothers with a twin pregnancy start to show their bumps sooner than mothers expecting one child. Your pregnancy bump-starts becoming more prominent and it’s time to tell people you haven’t already! Keep reading to find out about what happens in the next few weeks:

Twin Pregnancy: 14-17 Weeks

Symptoms of the mother

- If pre-pregnancy, your weight was normal, your doctor may advice you to gain 15-18 kgs over a period of the next nine months. Medical experts recommend adding about 600 calories to your diet each day if you are expecting twins. - As time progresses, your belly and uterus begin to expand. You will start to notice a change in your posture or shift in the center of gravity of your body. This places additional strain on your back which may cause lower back pain. You consult your doctor to guide you through safe and easy exercises that will ease your pain and help you strengthen your muscles.

Development of twins

- Between the period of 14-17 weeks, your baby’s sex organs will start to develop. However, you may not find the gender of the baby for up to 20 weeks.

- At around 16 weeks, your babies can now slowly move their eyes behind their lids. They are unable to open their eyes, as they are fused shut. Your twins will also have eyebrows and eyelashes.

- Your baby will start to make small movements in this period. There will be an increase in activity and it won’t be long before you start to feel your twins moving around your belly.

Twin Pregnancy: 18-22 Weeks

Symptoms of the mother

- As the week progresses, your belly keeps growing too. This might make it difficult to get a good night’s sleep. You can use pillows while sleeping on the side, to support your belly and also place a cushion between your knees to help you sleep better.

- With the growing belly, your skin starts to stretch. The stretching of your skin along with hormonal changes weakens the elastic tissue under your skin. This causes the appearance of stretch marks and your skin may also become itchy. Stretch marks aren’t preventable, but you can hydrate your skin by applying a thick moisturizer, which can help reduce the itchiness, and by consuming water.

- The increase in blood volume while being pregnant can lead to a few changes in your circulation. This may make you feel lightheaded. If you feel lightheaded during your twin pregnancy, try to move around with caution and lie down on your side, if possible.

- Between 18-22 weeks is when you’ll start to feel the movements of your babies for the first time. In some twin pregnancies, it happens earlier than this too. This process is called ‘quickening’. Each pregnancy is unique, so if you haven’t felt the babies move yet, do not be afraid. If you are concerned, talk to your doctor. Once the baby starts to move, your doctor may ask you to count the movements made by your little ones.

Development of twins

- Your twins will develop the sucking reflex, which enables them to breastfeed after being born. If a hand floats up to their mouth, they might suck their thumb. - Your babies may begin to hear by 18 weeks. Ears will start to develop at the side of their head too.

- At this period of pregnancy, your baby’s skin starts to get a greasy coating called vernix. This coating helps protect your baby’s skin from the amniotic fluid.

- Your baby’s skin will also start to develop a fine, downy protective layer of hair. This is called the lanugo. Lanugo helps the vernix adhere to the skin of your babies, which protects them from the amniotic fluid.

Twin Pregnancy: 23-27 Weeks

Symptoms of the mother

- Your body goes through hormonal changes and a faster metabolism during pregnancy. This results in your body to generate more heat than before, resulting in hot flashes. Wearing loose, breathable, and comfortable clothes and hydrating yourself during your twin pregnancy, ensures that you are staying cool.

- As an expecting mother, every time you go in for a prenatal checkup, along with other your blood pressure will be monitored. This is to make sure that the to-be mom is safe and sound and also on the lookout for preeclampsia. Preeclampsia is a blood pressure disorder that is slightly more common in twin pregnancies as compared to singleton pregnancies. If you notice, swelling of hands and face, constant headaches, change in vision, or difficulty in breathing well, you need to contact your doctor right away.

Development of twins

- Your twins will start responding to sound. Your babies will react to familiar or loud sounds. This may include a song or a parent’s voice. They react to the sound by moving around in the belly.

- Between 23-27 weeks, the twins would have started to form ridges on their palms and soles of their feet. These ridges later become your baby’s footprints and fingerprints.

- At around 26 weeks, your twins will start producing ‘surfactant’. This helps the air sacs of the infant stay inflated. This is an important development in your babies as it enables them to breathe outside the womb.

- Your twins will also be to make grasping motions with their hands in this period.

Third Trimester: Symptoms and Development

The symptoms and the pain may be getting intense in the third trimester, but we are almost at the crossing line!

Twin Pregnancy: 28-32 Weeks

Symptoms of the mother

- The expecting mother may pain in her hip and pelvic region in the third trimester. This pain is likely to go away after your babies are born. If your feet or leg feel numb, it is advisable to call your doctor immediately.

- In the third trimester of your twin pregnancy, your body starts to prepare for the delivery of the baby. The mother may start feeling contractions. This doesn’t necessarily mean you are going into labour. These practice or false contractions are called ‘Braxton Hicks Contractions’. The main difference between real contractions and Braxton Hicks Contractions is that your cervix doesn’t dilate during the latter. You can consult your doctor to help resolve any doubts you may have. Braxton Hicks contractions occur at irregular periods and do not increase in intensity like real labour contractions.

- An expecting mother may develop hemorrhoids in her third trimester. This is because of the extra blood flow to the pelvic region, along with the pressure of a larger uterus. Hemorrhoids are painful veins around the rectum. Consuming a high fiber diet along with warm baths can help relieve the pain and discomfort.

Development of twins

- At around 28 weeks, your twins will be able to open and close their eyes. They may also be able to sense the change in light. Most of their time is spent in rapid eye movement (REM) sleep, with their eyelids shut.

- At 32 weeks, your twins may start to shed their lanugo.

- Your baby’s brain will now be developed enough to control body temperature. This ensures that the babies are less reliant on amniotic fluid for warmth.

- The bones of your twins will start to harden, however, the skulls of babies are still soft, so they can pass through the birth canal more easily in case of a vaginal delivery.

Twin Pregnancy: 33-36 Weeks

Symptoms of the mother

- Your legs and feet may be swollen due to fluid retention. To help reduce the swelling you can elevate your feet. If you have sudden or severe swelling in your feet, it could be a sign of preeclampsia. Contact your doctor if you have concerns regarding your swelling.

- Carrying twins can be difficult! You are bound to experience fatigue and tiredness. Make sure you take naps throughout the day and try to engage in light exercises that will help you be mobile.

- If you notice a swelling in one leg, which is accompanied by pain in the calf region and redness and warmth around the calf area, it may be a case of deep vein thrombosis. It is not very common in twin pregnancies, but it could occur if the expecting mother is placed on bed rest. There isn’t anything to worry about, contact your healthcare provider to get advice on how to reduce the pain.

Development of twins

- Your baby’s vital organs continue to develop. Their lungs are in preparation to breathe outside the womb. Your twins’ circulatory and musculoskeletal systems are almost completely developed.

- Your little babies will continue to put on fat and gain weight. Most twin babies are smaller than singleton babies when born. Each baby will weigh around 3 kgs on average.

Twin Pregnancy: 37-40 Weeks

Symptoms of the mother

A very common symptom in the last few weeks among expecting mothers is snoring. There is nothing to be ashamed about if you’ve been snoring. It happens due to changes in breathing at the end of your pregnancy. You can try using nasal strips or a humidifier to help you breathe better.

- With two babies in your belly, it can be challenging to move around. Make sure to take things slowly and relax frequently.

Development of twins

- Your twins are now getting ready to come into the world. They will move into an optimal position for vaginal delivery. Either both the babies will have their head towards the vagina or only one of the twins has their head down or both have their feet towards your vagina. Your doctor will check their position and give know what to do, no matter what.

- Your babies continue to develop in the last few weeks of being in the womb. The vital organs are developed enough for life outside of the womb. But some organs, like the brain, continue to grow for many years.

Labour during twin pregnancy

As compared to singleton pregnancies, twin pregnancies can be slightly more ‘high risk’. There is a possibility of preterm birth, which is a common phenomenon in twin pregnancies. More than 50% of twins are born before 37 weeks. Your doctor will be working on getting the best outcome for you and your baby, so both the parties are safe and sound. In some cases, your healthcare provider may recommend inducing labor before your due date to avoid complications. In the case of a twin pregnancy, there is a higher chance of the mom 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 doctor 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. Twins come with their share of challenges, but they're a treat. You’ve surely hit the baby jackpot!

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