There is no evidence to suggest that stopping sex is necessary in pregnancy, nor that sex will cause a miscarriage or other problems in early pregnancy. Whether or not you have sex will obviously depend on how you feel – sometimes you may not feel like having sex because of other things like sickness or nausea. It is obviously your decision and you should discuss this with your partner.
If you have had some bleeding in early pregnancy, you will understandably be more worried. Again, there is no evidence that having sex will cause you to miscarry, but you may be advised by professionals to abstain from sex until the bleeding has settled down and stopped. This is really so that you do not have more bleeding and cause yourself to worry. Sometimes the bleeding can come from the neck of the womb (cervix) and leaving sex for a few days will let that settle down. If you bleed every time after sex, you should contact your GP and ask to be seen.