As long as your sperm enters the vagina, your partner can still become pregnant.
However, if you ejaculate before penetration, your partner won’t be able to conceive - this might occur frequently if premature ejaculation is a problem for you.
The pressure of trying to have a baby may be causing you anxiety and stress, which can make your premature ejaculation more severe.
If you and your partner are trying to conceive and premature ejaculation is getting in the way, speak to your doctor for advice and suitable treatments.