Intrauterine pregnancy is when a fertilized egg implants and grows in the correct place – your uterus. Not all early pregnancies develop typically. An ultrasound is the only way to confirm that implantation occurred in the right place.

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Pregnancy is a remarkable journey starting with the fertilization of an egg and implantation. Every early sign and symptom of pregnancy can be exciting but also raise many questions.

How do you know if your pregnancy is developing in the right place? Ultrasound is your answer.

There are many aspects of intrauterine pregnancy to explore, including stages of pregnancy, what you can expect, and the risks during early pregnancy.

An intrauterine pregnancy is when a fertilized egg travels down the fallopian tube and implants in the lining of your uterus. Here it grows and develops from an embryo to a fetus and, finally, a baby.

If the pregnancy is not in your uterus, it’s ectopic. According to the American Society for Reproductive Medicine, an ectopic pregnancy occurs in 1–2% of all conceptions.

Ectopic pregnancies cannot survive. If a pregnancy becomes ectopic, you will need immediate medical treatment. Treatment for ectopic pregnancy is generally medication or surgery.

If an ectopic pregnancy progresses too far, the embryo can grow too big, causing a fallopian tube to rupture. This is a medical emergency because there may be significant internal bleeding. Early treatment can prevent more serious complications.

Learn more about ectopic pregnancy, how one is diagnosed, and the treatment options.

Early pregnancy comes with many signs and symptoms, including:

None of the symptoms confirm that your pregnancy is in your uterus and not ectopic. Symptoms of an ectopic pregnancy to watch for include:

Blood tests detect the pregnancy hormone hCG and can tell if you’re pregnant as early as 6–8 days after ovulation. Blood tests can give a positive or negative result or an amount of hCG hormone.

Urine pregnancy tests detect the hCG hormone as soon as 1 day after you miss your period. These tests become more accurate the longer you wait.

An ultrasound done with a probe in your vagina called a transvaginal ultrasound will show a fluid-filled sac (gestational sac) around the embryo in your uterus as early as 4 1/2 to 5 weeks from the first day of your last menstrual period (LMP).

Ultrasound is the only way to confirm that you have an intrauterine pregnancy.

Experts calculate pregnancy in days and weeks. A full-term pregnancy is 40 weeks or 280 days from the first day of your LMP. During the first 2 weeks, you’re not even pregnant.

Most people use months or trimesters to describe the stages of pregnancy.

First trimester

The first trimester is from the first day of your LMP through 12 weeks. Your egg fertilizes and implants in your uterus during this time. All the major organs develop.

You can expect the following signs and symptoms:

You may even lose a few pounds.

Second trimester

The second trimester lasts from 13–27 weeks. Your fetus grows and develops rapidly.

You may experience the following:

Third trimester

The third trimester is measured from 28 weeks until delivery, around 40 weeks. During this time, your fetus gains weight, and their organs mature.

You can expect:

An intrauterine pregnancy is the desired and most common type of pregnancy. But some pregnancies cannot survive or are called nonviable.

If you have any of the following situations, the pregnancy is nonviable and requires medical attention:

  • Chemical pregnancy: A chemical pregnancy happens when a fertilized egg does not implant properly.
  • Blighted ovum: A blighted ovum happens when a fertilized egg stops developing after a gestational sac forms in the uterus.
  • Ectopic pregnancy: An ectopic pregnancy happens when a fertilized egg implants outside the uterus, most often in a fallopian tube.
  • Spontaneous abortion or miscarriage: A spontaneous abortion or miscarriage happens when an intrauterine pregnancy stops developing, and your body expels it from the uterus before 20 weeks.
  • Missed abortion: A missed abortion happens when an embryo or fetus is without heart activity, and a miscarriage does not spontaneously happen.
  • Molar pregnancy: In a molar pregnancy, a tumor develops in the uterus early in pregnancy because of a genetic error.
  • Stillbirth: A stillbirth is the loss of a pregnancy after 20 weeks.

While not all of these are preventable, you can work closely with your OB-GYN on your pregnancy care to ensure you’re doing everything possible to maintain a healthy pregnancy.

Most pregnancies, 90% once confirmed, lead to the birth of a baby. If you suspect you may be pregnant, it’s important to consult a healthcare professional. Prenatal care is a vital part of having a healthy intrauterine pregnancy and delivery, and early prenatal care is a great way to start your pregnancy.

However, pregnancy loss is possible. Around 10% of all pregnancies may end in loss, and up to 26% of pregnancies, including ones not yet confirmed, may end in miscarriage.

If I’ve had an ectopic pregnancy before, what are the chances of it happening again?

Ectopic pregnancies can happen again, but there’s no sure thing. Evidence suggests that if you’ve had one, your chance of it happening again is 10–27%.

If you’ve had an ectopic pregnancy, reach out to your doctor if you’re concerned about a future one.

What can I do to increase my odds of having an intrauterine pregnancy?

Most importantly, prevent or treat sexually transmitted infections (STIs) like chlamydia. Infections can cause scarring in your fallopian tubes.

Not smoking will also increase the likelihood of implantation occurring in your uterus.

Can I have a healthy pregnancy after having a pregnancy loss?

Yes, most women who have had a pregnancy loss can go on to have a healthy intrauterine pregnancy.

Factors such as the cause of the previous pregnancy loss and underlying health conditions affect the likelihood of a successful future pregnancy. Each person’s situation is different.

Intrauterine pregnancy occurs when a fertilized egg implants inside of your uterus. An ultrasound will confirm that your pregnancy has indeed happened in your uterus.

With healthy implantation, the embryo develops and grows. Pregnancy has three stages called trimesters. Each trimester has joys and challenges.

Because of the many risks associated with pregnancy, it is vital to have regular prenatal care.