Whether you’re trying for a baby or not, wondering if you might be pregnant can be a stressful time. You might be aware of classic pregnancy symptoms like nausea and a missed period, but how can you tell if you’re pregnant after what’s considered to be your first week of pregnancy? Spoiler alert: The truth is that you can’t, because pregnancy symptoms don’t actually exist this early on. That's because conception hasn’t taken place at this stage, meaning you’re not actually pregnant yet, which can be more than a little confusing!
Keep reading to learn more about what’s likely to be happening in your body at 1 week pregnant, with insight from Dr. Jenna Flanagan, academic generalist obstetrician and gynecologist, Massachusetts, US.
Your pregnancy at 1 week
Let’s start with a look at how the weeks of your pregnancy are counted. Technically speaking, at 1 week pregnant, you’re not actually pregnant yet. This means that you can’t tell if you’re pregnant in your first week of pregnancy — you would only be considered 1 week pregnant in hindsight.
Confused? We hear you. Let’s break this down a bit. Gestational age and fetal age are actually two different things. Your gestational age — or how long you’ve been pregnant — is calculated from the start of your last period. In comparison, the fetal or conceptional age is the actual age of your baby. So when we talk about being 1 week pregnant, we’re referring to your gestational age.
“Pregnancy is dated by the first day of the previous menstrual cycle prior to diagnosis of pregnancy,” explains Dr. Flanagan. “Therefore, the first week of pregnancy is before ovulation. This is the first week of the follicular stage (the phase of the menstrual cycle when an egg is maturing), which happens before an egg is released from the ovary and fertilization happens.”
Counting your pregnancy week by week in this way can definitely feel confusing at first. But don’t worry, if you do become pregnant, it will feel more natural as you go on. And don’t forget that you can also figure out when your baby might arrive using our handy due date calculator.
It’s worth noting that if you have irregular cycles (which means your cycle length varies by more than seven to nine days), then dating your pregnancy from your last period can be tricky. As Dr. Flanagan explains, “If the cycles are irregular, often dating by the first day of the last menstrual cycle can be inaccurate or misleading.” Why? “Because ovulation occurs at vastly different times in people who have irregular cycles,” she says.
Don’t worry, though. This simply means you may need to confirm your exact pregnancy dates through an early ultrasound scan once you’re a bit further along in the first trimester. “Blood hormone levels can give a general idea of which week of pregnancy you’re at,” explains Dr. Flanagan. “But an early ultrasound can then confirm the dating of the pregnancy. This typically occurs between 5 to 7 weeks.” However this ultrasound can also be done slightly later, up to 13 weeks of pregnancy.