Hope I will be able to sort your problem out.
Every newly married couple faces this issue of confusion.The failure rates of condom usage is rated to vary from 2-15% if the couples have regular sex for a year.Now,if you want to avoid it,then its important that you know the safe period and calculate the safe days.
Eggs producing phase known as Ovulation in medical terminology,approximately occurs in the middle of the cycle, i.e. duration of the menstrual cycle - 14 days (taken as a standard) and 7 days prior or 7 days after the day of ovulation is considered dangerous days(chances of pregnancy
So,avoiding the week before and a week after the ovulation is considered safe period and can avoid pregnancy even if the condom is not used.
First, you should know the duration of the cycle,which varies from one women to the other(taking into consideration that all months have 30 days).Its better that you are given an example i.e. first day of the last period(eg.1.02.13) to the first day of the present period(2.03.13),the interval is the known as duration of the menstrual cycle. So,in this case the duration would be 31 days.
Now,consider another month of previous menstrual cycle e.g(5.12.12) and (1.01.13).In this case the duration is 26 days.
So,your wife's cycle duration varies from 26-31 days.
Now,longest duration subtracting 10(standard) i.e 31-10 which is equal to 21.
No, shortest duration subtracting 18(standard)i.e 26-18 which is equal to 8.
Therefore, the 8th-21st day from the first day of periods is dangerous period.Avoiding these days,sexual intercourse is safe.
Morever,I would ask you husband to practice what is known as "COITUS INTERRUPTUS".It is the withdrawal or pull-out method(a method of birth-control) in which a man, during intercourse withdraws his penis from a woman's vagina prior to orgasm and ejaculates outside the vaginal(better if ejaculates completely outside the genital area of a woman).If this is well practised the intimicacy can be done regularly.
Hope,I could explain you well.Hope to be reviewed.