The mortality rate for sperm is very high and only a few dozen ever make it to the egg. The rest get trapped, lost (they may head up the wrong fallopian tube) or die along the way. For the few that get near the egg, the race isn’t over. Each one has to work frantically to penetrate the egg’s outer shell and get inside before the others. The egg needs to be fertilised within 24 hours of its release. When the hardiest sperm of the bunch makes it through, the egg changes instantaneously to prevent any others getting in. It’s like a protective shield that clamps down over the egg at the exact moment the first sperm is safely inside. The uterus is a muscular bag with a soft lining. The uterus is where a baby develops until birth. The cervix is a ring of muscle at the lower end of the uterus. It keeps the baby in place during pregnancy. Part of the tip of the head of the sperm releases enzymes to digest the egg membrane to allow fertilisation to take place.

The sperm that survive still have a long road ahead. In all, they need to travel about 18cm from the cervix through the womb to the fallopian tubes. That’s the equivalent of a human being swimming 100 lengths of an Olympic swimming pool! The fastest swimmers may find the egg in as little as 45 minutes. It can take the slowest up to 12 hours. If the sperm don’t find an egg in the fallopian tubes at the time of intercourse, they can survive inside you for up to seven days. This means that if you ovulate within this time window you could still conceive.BabyCentre's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organisations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

NHS. 2019. How can I tell when I'm ovulating? Common Health Questions. www.nhs.uk Opens a new window [Accessed May 2020] Its main function is to allow the exchange of materials such as oxygen and nutrients between the fetus and mother whilst removing waste substances such as carbon dioxide and urea. This relies on a process called diffusion as there is no mixing of maternal and fetal blood in the placenta. Dode MAN, Caixeta FMC, Vargas LN, Leme LO, Kawamoto TS, Fidelis AAG, Franco MM. Dode MAN, et al. J Assist Reprod Genet. 2023 Apr;40(4):943-951. doi: 10.1007/s10815-023-02758-3. Epub 2023 Mar 3. J Assist Reprod Genet. 2023. PMID: 36864182Each ovary is connected to the uterus by an oviduct. . The oviduct is lined with cilia, which are tiny hairs on cells. As part of the menstrual cycle, an ovum develops, becomes mature and is released from an ovary. The cilia move the ovum along the oviduct and into the uterus. Hirsch IH. 2019. Overview of male sexual function. www.msdmanuals.com Opens a new window [Accessed May 2020] From start to finish it takes about 10 to 11 weeks to create a new sperm cell. Both diet and lifestyle can make a difference to sperm quality. The average sperm lives only a few weeks in a man’s body and each ejaculation can set free up to 400 million sperm. This means that men have to make sperm continuously throughout their adult lives. You are not actually pregnant until the blastocyst embryo has attached itself to the wall of your womb, where it will develop into a fetus and placenta. Occasionally, the blastocyst will implant somewhere other than the womb (usually in the fallopian tube). This is called an ectopic pregnancy, and it needs urgent medical attention. The pregnancy will not survive outside the womb and needs to be completely treated or removed. The placenta is an organ responsible for providing oxygen and nutrients, and removing waste substances. It grows into the wall of the uterus and is joined to the fetus by the umbilical cord. The mother's blood does not mix with the blood of the fetus, but the placenta lets substances pass between the two blood supplies:

An opening between the uterus and vagina called the cervix, allow sperm in and menstrual blood out. The vagina, or birth canal, connects the cervix to the outside of the body. NHS. 2018. Trying to get pregnant. Health A to Z. www.nhs.uk Opens a new window [Accessed May 2020]FPA. 2018. Bodyworks. Your guide to understanding reproduction. Family Planning Association. Derby: McCorquodale. www.sexwise.fpa.org.uk Opens a new window [Accessed May 2020] Deans A. 2018. Your new pregnancy bible. The experts’ guide to pregnancy and early parenthood. 4th edn. London: Hamlyn. The Sperm Meets Egg Plan is a step-by-step guide to achieving pregnancy without taking invasive tests, charting temperatures, or making mistakes in predicting your ovulation that result in mistimed attempts at fertilization.

Komondor KM, Bainbridge RE, Sharp KG, Iyer AR, Rosenbaum JC, Carlson AE. Komondor KM, et al. J Gen Physiol. 2023 Oct 2;155(10):e202213258. doi: 10.1085/jgp.202213258. Epub 2023 Aug 10. J Gen Physiol. 2023. PMID: 37561060 The male reproductive system has two testes (singular: testis). These are contained in a bag of skin called the scrotum. The testes have two functions: Before you start trying, you may want to understand more about your fertility and learn exactly how you get pregnant. Conception is the moment when egg and sperm meet. It can take anything from 45 minutes to 12 hours for a sperm to reach your fallopian tubes, which is where conception usually happens. However, sperm can survive inside your body for up to seven days, so conception can happen at any point in the week after unprotected sex, if you’re ovulating. Inside the woman’s body: how an egg is hatched When the nucleus of a sperm and egg fuse together, the egg is fertilised and it develops into a fetus. Each cycle an egg travels from an ovary through the oviduct to the uterus or womb, where it settles.Deanna Roy is the six-time USA Today bestselling author of women's fiction. She is a fierce advocate for all the children in her care, biological, fostered, and adopted, and the mothers, who like her, lost babies to miscarriage. To make female sex hormones, which affect the way bodies develop and also regulates the menstrual cycle. In male reproductive organs, the scrotum holds the testes, which produce sperm and sex hormones, including testosterone. During ejaculation, the sperm pass through the sperm duct and combine with seminal fluid produced by the glands to create semen, which exits the body through the penis.