Conception 101
Conception happens when an egg meets sperm in the fallopian tube (fertilization), but pregnancy only starts if the fertilized egg (embryo) successfully implants in the uterus. About half of embryos never implant. To get pregnant, you need ovulation, fertilization, and then implantation — timing is everything. Home pregnancy tests detect a hormone (hCG) after implantation, so wait until your period is late for the most accurate result. If you don’t want to get pregnant, use regular birth control or condoms. If you have unprotected sex, the Julie Morning After Pill (or other forms of OTC levonorgestrel like Plan B) can help prevent pregnancy if taken within 72 hours — the earlier the better
“Conception" gets thrown around a lot when it comes to pregnancy, but it has a very specific meaning in the medical world. It’s just one part of the multi-step process of becoming pregnant, which starts with ovulation and ejaculation and concludes with a successful implantation.
Read on to learn what conception is, the additional steps that lead to pregnancy, and when to take a pregnancy test.
What is conception?
Conception is the term used to describe the merging of the egg and sperm in the fallopian tube, also known as fertilization. In order for this to happen, an egg has to be released from an ovary during ovulation and sperm must travel through the vagina and uterus.
After conception, the now-fertilized egg (called an embryo) must successfully implant in the uterus for a pregnancy to begin. However, there are a variety of reasons why implantation does not happen, and the embryo will pass out of the uterus on its own. About 50% of embryos don’t implant in the uterus. It’s also possible for the embryo to briefly attach and then detach shortly thereafter, something called a chemical pregnancy. This may look like a slightly delayed period with a little more bleeding than normal.
How does a pregnancy start?
Pregnancy begins when the embryo successfully implants in the uterus and then continues to grow and develop. Timing is everything when it comes to pregnancy. Here's the breakdown of the steps that are essential for a pregnancy to happen:
- Ovulation. Ovulation takes place in between your periods and refers to the process where a mature egg is released from the ovary into the fallopian tube. Once released, the egg can survive for 24 up to hours. If you have a 28-day cycle, ovulation generally occurs around day 14, but since each cycle is different, the exact day of ovulation can differ for any number of reasons. If you track your menstrual cycle, you may have a rough estimate of what days you're ovulating. There are some symptoms that can help you tell if you’re ovulating, such as cramping, changes in body temperature, or cervical mucus.
- Fertilization. Fertilization is the fusion of an egg and sperm within the fallopian tube. Following ovulation, an egg travels to the fallopian tube, where it stays for 12 to 24 hours. Sperm reaches the fallopian tube by traveling through the vagina, cervix, the uterus, and finally into the fallopian tube. Each single ejaculation contains millions of sperm and it only takes minutes for the sperm to travel from the vagina to the fallopian tube.
- Implantation. Implantation is when the embryo attaches to the uterus. This usually happens about 7 days after fertilization. At this point the cells of the embryo have divided (through a process called mitosis).
When to take a pregnancy test
At-home pregnancy tests work by detecting a hormone present in your urine known as human chorionic gonadotropin (hCG). Also known as the "pregnancy hormone," hCG levels increase after the embryo has implanted onto the uterus. Levels are low at first, and home tests differ in how early they can detect a pregnancy based on how sensitive they are. The most sensitive urine pregnancy tests can detect hCG in the urine 3-7 days after implantation (as early as 10 days after conception). If taken too early, it may show an incorrect result. For a more accurate result, wait to take the test until you notice your period is late.
What if I don't want to get pregnant?
If you have sex regularly and don't want to get pregnant, use a regular form of birth control like the daily pill, IUD, ring, shot, implant, or patch. Barrier methods like condoms can also help prevent pregnancy and help to protect you from giving or contracting STIs.
If you had unprotected sex and want to prevent conception and pregnancy, use the morning-after pill, as soon as possible. The Julie Morning After Pill™ (levonorgestrel) tablets and other morning-after pills can help prevent pregnancy up to 72 hours after unprotected sex, but they’re most effective the sooner you take them. Morning-after pills are available online and in-stores at Target, CVS, Walmart and Amazon or get it delivered now through GoPuff, UberEats, Instacart and Doordash. They're legal in all 50 states and FDA-approved. No ID, credit card, parent, or insurance is required to purchase — ever.
While we love to share useful and helpful information, the above shouldn’t replace the advice of your healthcare professional. For questions about birth control and other women’s health issues, please talk to your doctor.
Julie wants to keep young women in the driver’s seat of their own stories and provide them with the tools necessary for a happy, healthy sex life.
We know (and have lived!) through the ups and downs of young adulthood firsthand, and we aim to normalize the events, conversations, and questions that come during this period to help destigmatize sexual health. We believe women should live life with total freedom — starting with their ability to choose how, when, and if they become pregnant.
We know that women can make the best choices for themselves when equipped with the right information. We don’t take sexual education lightly and are committed to sharing accurate and factual information through rigorous planning and QA processes. In fact, all Julie content is reviewed by at least two board-certified doctors on our medical board. Learn more about them here.
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Tessa Commers, MD, FAAP, MS is a board-certified pediatrician based in the Seattle area with a particular interest in adolescent health and sexual education. In addition to clinical practice and serving as Head of Medical at Julie, Tessa also founded AskDoctorT — an education platform with over a million followers across Instagram, TikTok, and YouTube — aimed at improving adolescent health literacy and body confidence. She also hosted and wrote the puberty podcast “That’s Totally Normal!” and has contributed to peer-reviewed publications and educational initiatives focused on child and adolescent wellbeing.
Education: Children’s Mercy Hospital, Kansas City – Pediatric Residency; University of Nebraska Medical Center – Doctor of Medicine (MD); University of Nebraska Medical Center – Master of Science (MS, Genetics, Cell Biology and Anatomy); New York University – Bachelor of Arts (BA)
Cordelia Nwankwo, MD, FACOG is a native of Dallas, Texas. She graduated from Texas A&M University with a Bachelor of Science in Biomedical Engineering. She then earned her medical degree from The University of Texas Southwestern Medical School. Dr. Nwankwo completed her training in Obstetrics and Gynecology at UT Southwestern Medical Center and Parkland Hospital. She currently is in private practice in Washington, DC. Dr. Nwankwo’s goal as a provider is to make sure every patient feels heard and able to achieve optimal health.
Education: UT Southwestern Medical School – Doctor of Medicine (MD); Texas A&M – Bachelor of Science (BS)
