1. It may only take one sperm to fertilise an egg, but when you have sex around 100,000 of your partner's little swimmers surf into your cervix to for their shot at baby-making glory.
2. 24 hours is the time it takes for the sperm to enter the egg and fertilise it.3. About two percent of all pregnancies involve twins. Identical twins occur when one egg is fertilised by one sperm, then divides into two separate zygotes (the cell that becomes a baby). Non-identical twins are conceived when two separate eggs are released and fertilised by two separate sperm. Non-identical twins run in families, but identical twins appear to be completely random.
4. Boy or girl? Your fella is the one who decides. All eggs carry a single X (female) chromosome, while sperm carry either an X or a Y (male) chromosome. If an X sperm fertilises your egg, it's a girl; if a Y makes it in, you're having a boy.
5. At just six weeks pregnant, your baby has a heartbeat but is still only the size of a lentil.
6. Are your jeans feeling tight? At six weeks, your uterus has already expanded from the size of a plum to the size of an apple.
7. At eight weeks, your baby is officially classed as a fetus, which means 'little one' in Latin. Aww!
8. At 10 weeks, your baby can already respond to touch. If you press your tummy, she'll wriggle away. Not that you can feel it yet.
9. All of your baby's major organs – including heart, lungs, kidneys, brain and intestines – are formed and fully functional by 10 weeks. Now she just has to do some serious growing.
10. At 12 weeks, 20 teeth have formed in your baby's gums.
11. Your baby has her own unique fingerprints at just 13 weeks.
12. Your baby has peachy fuzz on her head from as early as week. She also has eyebrows and eyelashes, and is covered all over in lanugo – downy hair that helps to keep her warm.
13. At your 20-week scan, you'll see a proper little person, fully formed and more or less in proportion. Her trunk and limbs will grow more slowly from this stage onwards, but she will start laying down fat at an amazing rate, in preparation for being born.
14. A 21-week-old baby is the weight and length of a banana.
15. At 24 weeks, your baby's brain development is really taking off. She can tell the difference between your voice and your partner's, and research indicates that if you repeatedly play a piece of music while she's in the womb, she'll remember it after the birth.
16. Week 24 is one of the major milestones of pregnancy. At this point, your baby is classed as 'viable' – in other words, she would stand a good chance (around 39%) of surviving if she was born now.
17. Feeling a regular tapping sensation? It's probably just your baby having hiccups.
18. Did you know your unborn baby drinks (and then pees) the amniotic fluid? The whole amount is recirculated and replenished every three hours, so make sure you drink plenty of water to keep it topped up.
19. At 27 weeks, your unborn baby's eyes open, and in addition to distinguishing light from dark she learns to focus – although she'll only be able to see objects up to about 15cm away after birth.
20. At 40 weeks your placenta is the size of a large dinner plate, 2–3cm thick, weighs 650g and counts as a whole extra organ.
21. Counting down to your due date? Only five per cent of babies arrive on time so be prepared for your little one to arrive early or late.