Up until now, most newly pregnant women won’t have noticed anything significantly different about their bodies. Some women may have observed a spotting of blood or small pains around the time of implantation, and a woman using the charting method of tracking ovulation - measuring tiny fluctuations in basal body temperature - may have noticed that her temperature has remained high even though she is due a period (a potential sign of pregnancy).
During week four of pregnancy, your body is very active internally even if you don’t realise it! Several types of hormones are now rushing around your system, preparing all of the different organs and elements of your body for pregnancy and motherhood.The pregnancy hormone known as human chorionic gonadotropin (hCG), released by the placenta, provides you with two important hormones: oestrogen and progesterone. Oestrogen regulates the changes you will be experiencing over the next months in your uterine wall, breasts, and other body tissues, whilst the function of progesterone is to prepare the uterine lining to accept and maintain a fertilised egg during the first few weeks of your pregnancy.
A home pregnancy test measures the hCG hormone levels in urine. The hormone can be detected early on in a pregnant woman’s urine, but not immediately from the moment of conception—meaning that if you test too early, it is possible for the test to be negative even if you are pregnant. Though it is hard to wait when you are excited, do try to hold off on testing until at least the day that you would have expected to get your next period. Typically, it takes at least 10 days post implantation for hCG levels to rise high enough for pregnancy tests to detect. If you are taking fertility drugs, these can also affect the results of an at-home test, so you’ll probably need a blood test to confirm your pregnancy.
At this point, other pregnancy symptoms may well start to become apparent. The increased hormone levels, combined with increased blood volume, can make your breasts feel tender and sore. This is often one of the first physical symptoms of pregnancy that a woman experiences. Higher blood volume may also cause you to wee more often, as your kidneys are working overtime to clean that extra blood. You may feel generally tired, especially if you are also feeling nauseous. Additionally, you may notice your resting heart rate increasing slightly as your heart works harder to pump all of that blood around.
If you are expecting more than one baby, your symptoms will be the same, but are likely to be intensified.
Right now, your embryo is around the size of the full stop at the end of this sentence, and your body is hard at work creating supports that your baby will need over the next nine months, such as the placenta and umbilical cord.