Twin pregnancy week by week

4 weeks pregnant with twins
Read about the difference between identical and fraternal twins and find out what happens when the fertilized eggs attach to the lining of your uterus. Learn about how twins develop.

5 weeks pregnant with twins
Find out whether or not twins can be detected in week 5. If you’re pregnant, your body has already begun to produce the “pregnancy hormone” Human Chorionic Gonadotropin (hCG). You may test positive if you take a pregnancy test at this point.

6 weeks pregnant with twins
Your babies are developing rapidly. The sensitivity for negative side effects of alcohol, tobacco and certain types of medication is great in the days and weeks to follow.

7 weeks pregnant with twins
Your babies are growing at an amazing rate. You may be experiencing pregnancy symptoms. Find out more about how they can affect you.

8 weeks pregnant with twins
If you get a scan during this week you’ll see two miniature babies inside of you with round heads and arms and legs.

9 weeks pregnant with twins
Your babies important organs are formed and developing rapidly. You’ve probably started to gain weight.

10 weeks pregnant with twins
You might feel that your stomach isn’t working right. This is partly due to hormones and partly due to your growing uterus putting pressure on the bowels. Find out what you can do to feel better.

11 weeks pregnant with twins
Your babies faces take more shape, with eyes, ears, noses and mouths. No guarantees, but many women experience that nausea subsides around this week.

12 weeks pregnant with twins
Your babies are nearly fully developed. In many countries you’ll be advised to have a dating scan around this time. Find out what the sonographer will look for during an ultrasound scan.

13 weeks pregnant with twins
You’re now in the second trimester of your pregnancy. Your hormone levels are evening out as your placenta(s) becomes fully operational and starts to create the required progesterone.

14 weeks pregnant with twins
Your children’s hands can grasp at this point and their legs kick but you won’t feel it yet. Many women experience the first signs of life between week 16 and week 22.

15 weeks pregnant with twins
Your babies skin are covered by lanugo hair. Your children will have shed all or most of it before you give birth to them if you don’t give birth very prematurely.

16 weeks pregnant with twins
You’ll experience life soon. It should happen anytime between week 16 and week 22. When you’ll feel it, depends very much on the position of your placenta(s) and whether it’s your first time being pregnant.

17 weeks pregnant with twins
Your babies are at times very active. They can do somersaults – both forwards and backwards. Your uterus is growing continuously as your babies grow.

18 weeks pregnant with twins
Your babies sebaceous glands are starting to produce sebum – oil on the skin. Together with cells, that have sloughed off your babies skin, and shed lanugo hair, this becomes vernix. Find out how the vernix protects your babies.

19 weeks pregnant with twins
You should be offered an anomaly scan when you’re between 18 and 20+6 weeks pregnant. Find out what the sonographer will look for, and remember to let him or her know whether  you’d like to know the sex of your babies.

20 weeks pregnant with twins
You’re in the second half of your pregnancy. You might begin to notice that your navel is “turning inside out” because your uterus has grown bigger.

21 weeks pregnant with twins
Your babies kidneys and urinary tracts are working. Your uterus takes up quite a lot of space in your stomach, and acid reflux and heartburn might bother you. Find out how to cope.

22 weeks pregnant with twins
Your babies are listening inside your womb. They’re mainly able to hear sounds from your body and voice at this point, but sounds from the outside world also get through.

23 weeks pregnant with twins 
You may feel Braxton Hicks contractions. Your uterus will contract and feel tight or hard. Learn about the difference between Braxton Hicks contractions and labour contractions.

24 weeks pregnant with twins
You may notice swelling in your body during pregnancy. Find out why and how to remedy it.

25 weeks pregnant with twins
Your children’s internal organs – except the lungs – are fully developed. The progress of medical care in recent years means that your babies have better chances of survival than ever before if you give birth during this week.

26 weeks pregnant with twins
Women carrying twins often begin their maternity leave or go on sick leave around 26 weeks. Talk to your doctor or midwife about it and find out what they recommend.

27 weeks pregnant with twins
Your babies might not be as long or weigh as much as singleton babies at this point. It’s normal that twins weigh less than average and in general are smaller when they’re born.

28 weeks pregnant with twins
We still don’t fully comprehend how babies experience life in the womb. But scientists have discovered that babies are far more developed than previously thought. Find out how to communicate with your children before birth.

29 weeks pregnant with twins
You’re now in the third trimester of your pregnancy. By now,you should be able to feel your babies move every day. Read about how to react if you don’t or if you feel that one or both of your babies are less active than usual.

30 weeks pregnant with twins
Your babies lungs are almost mature. Your babies are practicing breathing. You may have very vivid dreams at this point in your pregnancy.

31 weeks pregnant with twins
Your babies can distinguish light from dark, feel, hear and taste what you’re tasting. You may feel that there’s not enough room in your belly and you may be bothered by acid reflux.

32 weeks pregnant with twins
Your children are often in a sought of “dozed-off” state between sleeping and being awake. There’s brain activity both when the babies are sleeping and when they’re awake.

33 weeks pregnant with twins
Your babies are practicing nursing inside your womb. They’re sucking on their fingers and toes. The space in your womb is tight by now.

34 weeks pregnant with twins
Premature labour is a risk when you’re expecting twins, so your doctor and midwife will monitor you closely. Read about early signs that you’re going into labour.

35 weeks pregnant with twins
If you give birth in this week, your babies may not need any medical treatment. They may be able to go straight to the maternity ward with you.

36 weeks pregnant with twins
Most babies born in this week have mature lungs. This means that your babies won’t need special help breathing if they’re born now.

37 weeks pregnant with twins
You may be fed up with being pregnant. You want to meet your babies. Hold on – next week is the official date for when your pregnancy is considered at term.

38 weeks pregnant with twins
Your babies are considered born at term, if you give birth in this week.

39 weeks pregnant with twins
Your children’s bones are still soft. It’s a good thing as it helps your babies through the narrow birth canal.

40 weeks pregnant with twins
Your doctors have probably insisted for weeks that you get an induction or c-section. Find out why.

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In this article

• Pregnancy test at 4 weeks
• Twin pregnancy symptoms at 4 weeks
• Baby size & development at 4 weeks
• How identical and fraternal twins develop
• 4 weeks pregnant with twins belly
• 4 weeks pregnant with twins ultrasound
• Twin pregnancy diet
• Gestational diabetes in twin pregnancy
• What you need to buy

What you need to buy

There’s not much you need to buy yet, but taking a folic acid supplement is crucial. Ideally, you should begin taking folic acid at least a month prior to you getting pregnant, and it’s very important that you start immediately, if you haven’t. Folic acid is a B vitamin and it’s standard for pregnant women and women who plan to become pregnant. Folic acid helps prevent neural tube defects. Neural tube defects are serious birth defects of the spinal cord and the brain. You need to take folic acid for the first 12 weeks of pregnancy. There are folic acid in prenatal multivitamin tablets as well.

Pregnancy test at 4 weeks

You may be able to get a positive pregnancy test result, when you’re 4 weeks pregnant with twins, but don’t count on it. You can buy pregnancy tests that promise early results up to six days sooner than your missed period. However, the longer you wait, the more conclusive the test result will be. The levels of the pregnancy hormone hCG need to be high enough to be detected by pregnancy tests. The pregnancy hormone tells your ovaries to stop releasing eggs. It also triggers increased production of estrogen and progesterone. These hormones keep your uterus from shedding its lining and stimulate the growth of the placenta(s). You won’t ovulate while you’re pregnant.* This also means that you won’t get your period.

*It’s possible for a woman to continue ovulating after becoming pregnant, but it’s very rare. It’s called superfetation if a woman becomes pregnant while already pregnant. Read more about it in different types of twins.

Twin pregnancy symptoms at 4 weeks

• Some women might notice spotting – or slight bleeding – for one or two days around the time of implantation. This is called implantation bleeding. It happens when the fertilized eggs attach to the inside of the uterus. After implantation, the lining of the uterus gets thicker, and the cervix is sealed by a plug of mucus. It will stay in place until the twins are ready to be born.

• Some women report feeling nauseous very early on when they are pregnant with twins. This is probably due to the hormonal changes you’re experiencing.

• Some women experience cramps similar to when you’re getting your period. It’s not necessarily a bad sign. Wait a couple of days to see if you get your period and, if not, take a pregnancy test.

Baby size and development at 4 weeks

Your babies (or baby)* are like two tiny balls – called blastocysts – and are already consisting of several hundred cells that are multiplying. The part that will develop into the placenta(s) has started producing the pregnancy hormone human chorionic gonadotropin (hCG). The blastocysts are receiving oxygen and nutrients from their yolk sac(s) until the placenta(s) is ready to take over.

*If you’re having identical twins, the egg may not have split yet.

When you’re 4 weeks pregnant with twins, the fertilized eggs reach your uterus. With fraternal twins, two eggs have been released from your ovaries and have fertilized by two separate sperm cells. Identical twins stem from an egg splitting in two after fertilization. The eggs will now attach to the lining of your uterus. This is called implantation.

How identical & fraternal twins develop

Fraternal twins have their own separate placentas, amniotic sac and outer membrane. If an egg splits within the first three days after ovulation, identical twins will have their own placenta, amniotic sac and outer membrane similar to fraternal twins. This type of twin pregnancy is called a dichorionic-diamniotic (di-di) twin pregnancy. If the split happens later, the twins will share an outer membrane and placenta. In most cases, they each have their own separate, inner membrane. This is the case for two thirds of identical twins, so it’s the most common type of identical twin. This is called a monochorionic-diamniotic (mo-di) twin pregnancy. It’s possible for identical twins to share an inner membrane (amniotic sac) too, but it’s very rare and only happens in about one percent of identical twin pregnancies. This is called a monochorionic-monoamniotic (mo-mo) twin pregnancy. Twins who share a placenta are more at risk of twin pregnancy complications, so it’s very important to get a chorionicity scan early on.

4 weeks pregnant with twins belly

Your babies aren’t big enough for you to be showing at 4 weeks pregnant with twins. If you belly looks or feels a little bit larger than usually it’s probably due to blowing relating to the hormonal changes. Have a look at week by week twin pregnancy belly pictures from a lot of different twin pregnancies.

4 weeks pregnant with twins ultrasound

When you’re 4 weeks pregnant with twins, you won’t be able to detect the pregnancy by the use of ultrasound. When six full weeks have passed (after week 6+0) you should be able to detect all kinds of twins using ultrasound. The ultrasound picture above is of identical twins who share a placenta at 6+2 weeks. Read more about twin ultrasound and what you need to pay attention to.

Twin pregnancy diet

Eating healthy, nutritious food is important for you and your babies during pregnancy. You especially need to make sure that you get enough protein and calcium. You can get calcium and protein through dairy products, eggs, lean meat, lentils, peas, beans, chickpeas, soybeans, peanuts and vegetables such as kale and spinach. It’s very important that you cut down on sugar. Both in terms of candy and sugary drinks but also ready meals with added sugar. You increase the risk of getting gestational diabetes if you eat foods that are high in sugar.

Gestational diabetes in twin pregnancy

Gestational diabetes is a condition in which a woman without diabetes develops high blood sugar levels during pregnancy. It can not only affect your health but also the health of your babies. It makes you and your babies more at risk for type 2 diabetes, and your babies are more likely to be born too large. This makes them at risk of sustaining birth injuries or require a c-section delivery. They are also more at risk of being born prematurely, having low blood sugar and trouble breathing. You will be at risk of high blood pressure and preeclampsia. Luckily there are steps you can take to prevent or control gestational diabetes and reducing the risk of type 2 diabetes. Eating healthy foods and exercising can help reduce the risk of future type 2 diabetes. Of those women with a history of gestational diabetes who reach their ideal body weight after delivery, fewer than 1 in 4 eventually develop type 2 diabetes.

A total of 642 twin fetuses – with a total of 3078 ultrasound observations – were included in the study. Researchers developed a twin fetal weight chart for dichorionic twins in the second half of pregnancy. They also developed a twin fetal weight chart for monochorionic twins.

What does the study show?

The study showed, as expected, that monochorionic twins were consistently smaller than dichorionic twins. It also reaffirmed that twins generally are smaller than singletons.

The study showed twin fetal growth accelerates in the second trimester and continues in a linear pattern in the third trimester until term. This reduction in fetal growth is significant, particularly in the third trimester, compared with singletons.

It concluded that dichorionic twins deviates from singleton reference charts at approximately 32 weeks. Monochorionic twins deviates at 28 weeks. These deviations are one of the reasons why a singleton fetal weight chart shouldn’t be applied to twins.

The normal declaration of growth in twins can seem like an issue, even if it isn’t.

How do I read a twin fetal weight chart?

Fetal growth is better monitored with a doctor.

A twin fetal weight chart shouldn’t be used in isolation without all the other important pregnancy monitoring visits. Also be aware that there’s nothing wrong with your children being below the median weight. 

The median weight is the value for which 50 percent of the fetuses are bigger, and 50 percent are smaller. It  separates the higher half from the lower half.

To give you a better sense of how small or big your babies are, we’ve also included the 10th and 90th percentile.

What’s the 10th and 90th percentile?

If your babies estimated weights are equal to or less than the weight indicated as the 10th percentile, it means that your babies are among the smallest 10 percent. 

If your babies estimated weights are equal to or above the weight indicated as the 90th percentile, your babies are among the biggest 10 percent.  

If you’re worried about the growth of your babies, it’s important that you consult your doctor or healthcare provider.

Growth of twins is an important characteristic to be monitored along with other variables like The Fetal Non-Stress test (NST monitoring).

Estimated fetal weight in dichorionic twins

Estimated fetal weight in monochorionic twins

Only provisional guidelines regarding the optimal twin pregnancy weight gain were released, because the research on twin pregnancy weight gain was limited.

The amount of weight to gain is dependent on a woman’s pre-pregnancy body mass index (BMI). To meet the recommendations of the report, women need to gain within the weight gain ranges for their BMI category.

Unfortunately, there wasn’t enough data to provide sufficient information to develop provisional guidelines for underweight women pregnant with twins.

*In 2009 the NAM was called the Institute of Medicine (IoM).

Regardless of your weight and BMI, be sure to discuss your weight and weight gain with your doctor.

More women have twins

While some raise caution at the fact that excessive weight gain during pregnancy may be harmful to the mother and her babies, others have speculated that the provisional twin pregnancy weight gain recommendations may not be high enough to prevent low birth weight.

A small study questioned the twin pregnancy weight gain limits for normal-weight women. Over a five-year period, 170 patients in a New York City private obstetrics practice gave birth to twins at or near full-term.

Mothers who gained more than recommended did not have higher rates of gestational diabetes, high blood pressure or pre-eclampsia than women who put on less weight.

The more weight a mother gained, the more likely her babies were to be born weighing above five and a half pounds (2540 grams). Because of this, the clinic does not limit the amount of weight their patients gain IF they are a normal weight when they are entering pregnancy.

Today, a greater percentage of women are entering pregnancy overweight or obese.

Have a look at a Canadian study that explores outcomes for babies and mothers, who’ve gained weight below, within and above the NAM provisional guidelines.

Week by week guide
Have a look at our extensive twin pregnancy week by week guide. Find out how your babies are developing and what your body is going through. Look at pictures of other pregnant mothers and get pregnancy and birth tips.

Full term for twins
Find out what full term for twins means and what the probability is of giving birth at term. Find out when doctors believe that twins should be delivered.

How are twins formed
Do you know that there are more types of twins than identical and fraternal? Learn how twins are formed and find out about different kinds of identical twins. You need to be on the lookout for twin pregnancy complications and some complications relate to what type of twins you’re having.

Pregnancy complications
Read about the complications you might have to face being pregnant with twins. Find out how to treat them and how to know if you’re in preterm labour.

Pregnancy announcement
Look at pictures of how other families have announced twin pregnancies and find out how you can do a twin gender reveal.

Twin to Twin Transfusion Syndrome
Learn about this rare – but serious – disease, that only affects identical twins who share a placenta. Read stories about TTTS survivors.

Twin birth and pregnancy stories
Find out what other mothers felt and experienced being pregnant with twins. Read about premature birth, the first few weeks or months in the NICU and going home.

Not sure whether you’re pregnant with twins?

Learn about twin pregnancy symptoms. Find out how early can you detect twins and what you can do if you’d like to be pregnant with twins.