Birth control is not 100% effective so it is possible to get pregnant while on birth control. Pregnancies conceived while on hormonal contraception such as pills, patch, or ring do just fine. Pregnancies conceived with an IUD do have some risk,, but the risks are small.
It is scary for women who get pregnant while taking hormonal contraception. It is reasonable to worry that the hormones will hurt the baby. Surprisingly, it is extremely rare to see birth defects from hormonal contraceptives used in early pregnancy. This is true with birth control pills, the patch, the vaginal ring, or the shot. My advice is to stop the hormones as soon as the pregnancy test is positive, they are certainly not giving any benefit. Then don’t worry, it is extremely unlikely that they have harmed the baby.
The morning after pill is hormones that are taken after unprotected sex. These are taken as soon as possible, and certainly within 72 hours of the incident. These can keep ovulation from taking place and thus prevent pregnancy. This method is about 75% effective, so there can be a fair number of pregnancies from failure of this method. Women who become pregnant after using the morning after pill are not at increased risk of pregnancy complications or birth defects.
The IUD, also called IUS, is a device that is put in the uterus to prevent pregnancy. Although this is very effective, it is not 100%. Women who get pregnant with the IUD usually have normal pregnancies. It is important to see the doctor as soon as a pregnancy with an IUD is discovered. If a woman is pregnant with an IUD it is recommended to remove the IUD in the first trimester if the strings are accessible to the doctor. There is a small risk of miscarriage, but the risk of leaving it in is much greater. Often the strings are not visible on exam in an IUD related pregnancy. The most common reason for this is that the IUD is not present, it likely came out. This is why the pregnancy occurred. If the IUD is in place and the strings are not accessible or the pregnancy is in the second trimester or farther, it is generally advised to leave the IUD in. This can cause problems but the risks of problems from removal are greater in the second trimester or with missing strings. IUDs can cause infections during pregnancy which can lead to pregnancy loss. Having the IUD injure the baby is not impossible but it is very unlikely.