Week 1 Pregnancy Symptoms: What To Watch For (2023)

If you want to pinpoint the exact moment of pregnancy, it’s important to think about both fertilization and implantation. “A woman typically ovulates every month and in a normal case, fertilization occurs when the egg is picked up by the fallopian tube and the sperm makes its way through the uterus [to the] fallopian tube, and they meet there,” explains Salena Zanotti, M.D., an OB-GYN in Avon, Ohio.

The peak fertile window—in which fertilization is most likely to occur—is usually six days preceding ovulation up to the day of ovulation, according to the American Society for Reproductive Medicine.

“The human oocyte—the egg—has a lifespan between 12 to 24 hours, which is remarkably short,” says Tameka Zore, M.D., an OB-GYN, reproductive endocrinologist and a medical advisor at Modern Fertility. “Sperm have been shown to live in the female reproductive tract for up to three days, and some studies suggest possibly a couple days longer.” This means fertilization could occur days after sex.

While fertilization may serve as the introduction between an egg and sperm, pregnancy doesn’t actually start until implantation.

Implantation describes the moment when the fertilized egg travels down the fallopian tube to the lining of the uterus, which is where it will remain throughout pregnancy until delivery, explains Dr. Zanotti. This marks the official start of pregnancy.

“A series of complex biochemical processes need to occur to allow proper fertilization and implantation,” says Dr. Zore. Typically, she says implantation happens eight to 10 days after ovulation, but it can range anywhere from six to 12 days after ovulation.

With fertilization and implantation both complete, the pregnancy journey has officially started. So, what are the earliest signs to be aware of?

Missed Period

One of the earliest signs of pregnancy is a missed period, says Dr. Zore; this is often what prompts someone to take a pregnancy test. However, it’s important to know that this missed period may happen after the first week of being pregnant. Most people miss their period two weeks after conception since implantation tends to occur two weeks after ovulation—and therefore about two weeks before the next period starts.

The ovaries make estrogen and progesterone throughout the menstrual cycle to build up and stabilize the uterine lining. Pregnancy hormones will stimulate the ovaries to continue to make estrogen and progesterone so if someone is pregnant, they will not experience bleeding or a period. If there is no pregnancy to continue to encourage the ovaries to make these hormones, then the lining will shed and the person will get a period.

Breast Tenderness

Besides a missed period, Dr. Zanotti says that another one of the very earliest signs of pregnancy that can occur during week one is breast tenderness. “What happens during implantation is that cells are starting to form to become the placenta, and then you start getting more of the hormone human chorionic gonadotropin (hCG), which is produced by the placenta,” she says.

Once there’s hCG in one’s system, someone can start experiencing early pregnancy symptoms, including breast tenderness, she explains. Some people may experience breast tenderness in a specific spot, while others feel sore all over their breasts or under their armpits. According to a study in the Journal of Clinical Nursing, 76% of people experience breast tenderness during the first trimester^[1]Nazik E, Eryilmaz G. Incidence of pregnancy-related discomforts and management approaches to relieve them among pregnant women. Journal of Clinical Nursing. 2013;23(11-12):1736-1750. .

Nausea

“A lot of women experience nausea or an aversion to food,” Dr. Zanotti says, naming another early pregnancy symptom. To her point, nausea and vomiting was the top symptom people in the Journal of Clinical Nursing study experienced, with 88% of people experiencing this symptom^[1]Nazik E, Eryilmaz G. Incidence of pregnancy-related discomforts and management approaches to relieve them among pregnant women. Journal of Clinical Nursing. 2013;23(11-12):1736-1750. .

Just like breast tenderness, Dr. Zanotti says the reason for nausea is connected to the rise in hCG. People who experience nausea and vomiting during the first trimester tend to have higher levels of hCG than those who don’t experience these symptoms. While nausea and vomiting are no fun to deal with, these are normal symptoms of pregnancy and not cause for concern.

Fatigue

Both doctors say that fatigue is another common and normal symptom of pregnancy, including in the very early days. This is due to a change in hormone levels, not just with hCG but also progesterone. Progesterone levels rise significantly in early pregnancy. This stark change causes the heart to beat faster to help supply the developing placenta and fetus with more blood. But it can also make you feel more fatigued as a result.

Cramping

Since becoming pregnant puts a pause on getting your period, that means no uncomfortable premenstrual cramping, right? Not exactly. Both doctors say that experiencing cramping during early pregnancy is common. “Cramping in early pregnancy can be normal due to early expansion, including growth of the uterus in pregnancy,” says Dr. Zore. “Other causes can be due to gastrointestinal symptoms such as constipation, gas or bloating.”

If cramping is causing you severe pain or is accompanied by bleeding, Dr. Zore says it could be a sign of either miscarriage or ectopic pregnancy and it’s important to see your doctor.

Bleeding

Experiencing bleeding in early pregnancy can be stressful. There are several different reasons why this can occur, according to Dr. Zanotti. “The number one thing we worry about with bleeding in early pregnancy is a miscarriage,” she says. “Bleeding can be a sign of an abnormal pregnancy, which is called an ectopic pregnancy and happens when the pregnancy does not implant in the uterus.”

But this is not the only cause of bleeding in early pregnancy. “Sometimes, bleeding occurs from the implantation,” she adds. She explains that this is because when implantation occurs, it disrupts the lining of the uterus, causing light bleeding. If you have bleeding in pregnancy, review it with your own doctor to know what’s happening in your pregnancy.

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While all the week one pregnancy symptoms highlighted here offer good insight as to what could be happening in your body, the only way to know for sure if you’re pregnant is to take a test. “The best time to take a pregnancy test is generally at the time of the expected missed period,” says Dr. Zore.

Both doctors also say that some pregnancy tests can detect levels of hCG even earlier than this, five or six days before a missed period. “However, the sensitivity of most tests will be better the closer you are to the missed period, as hCG levels continue to rise,” adds Dr. Zore.

Even if you don’t experience any week one pregnancy symptoms, it’s still a smart idea to take a test if you think there’s a chance you could be pregnant. “A lack of symptoms can be normal,” says Dr. Zore. “It may vary when it comes to how far along a person is into pregnancy before they notice symptoms—if they notice specific symptoms at all.”

It’s important to note that some fertility medications will cause a false positive pregnancy test so if you’re in treatment, talk to your clinic about testing and what it can mean for you.

While bleeding is not a sure sign of miscarriage, Dr. Zanotti says it’s still a good idea to see a doctor if you have had a positive pregnancy test and then experience spotting or bleeding. “We want to know the reason for the bleeding,” she explains.

Even if you don’t experience bleeding during pregnancy, it’s important to make a doctor’s appointment after receiving a positive home pregnancy test result. It’s recommended to schedule the first prenatal appointment eight to 10 weeks from your last period. At this appointment, you will be able to find out your due date and your doctor will likely run blood tests.

“Certain blood types need to be managed differently,” adds Dr. Zanotti. For example, different blood types have different characteristics, and if the blood type between the pregnant person and baby are not compatible, it could have an impact on the immune system. Your doctor can also give tips on managing the pregnancy symptoms touched upon here as well as ones that are likely to come later.

Again, it’s worth reiterating that every person and every pregnancy is unique; there is not one universal pregnancy experience—and that includes what someone feels or doesn’t feel in that very first week. If you have any questions or concerns, talk to your doctor who can offer more insight.