http://www.babycentre.co.uk/a1013991/getting-pregnant-in-your-40s
From another link:
Risks to your baby
About one-third of all pregnancies in women ages 40 to 44 end in miscarriage. There are several reasons: The eggs may be defective to start with, the uterine lining may not be thick enough, or the blood supply to the uterus may not be rich enough to sustain a pregnancy. The risks of placenta previa (in which the placenta lies low in the uterus, partly or completely blocking the cervical opening and creating a high risk of hemorrhage) and placental abruption (in which all or part of the placenta separates from the uterine wall) are also increased. Babies born to women in their 40s are also more likely to have lower birth weights (under 5 1/2 pounds).
Risks of chromosomal birth defects rise steadily with each year into your 40s. If you give birth at age 40, your baby has a 1 in 106 chance of being born with Down syndrome and a 1 in 66 chance of being born with any chromosomal abnormality. But by age 44, those risks rise to 1 in 38 and 1 in 26, respectively.
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It is not a decision to be taken lightly, but then you already know that.
Hope you get it sorted between you.