I'm curious about what medical concerns an otherwise healthy, active and athletic woman who is pregnant at the age of about 35-37 would be?
I've got a female character who's a weekend warrior hiker/rock climber type character who would find out she's pregnant after a bout of nausea at her office. Would she, who's never been pregnant before, have any special medical concerns?
Pre-natal screening lab assistant here! The risk of Down's syndrome increases rather a lot after 35 - by the stats we use in the lab, the baseline risk for a 25 year old woman is roughly 1/1300. At 35 this rises to approx. 1/350, and at 45 it increases to 1/30 (for reference, we consider 1/150 the threshold for 'at increased risk', and usually amnio or CVS would be offered.)
It's worth noting that we don't calculate risks based on maternal age alone - other factors including N.T (nuchal translucency) biochemistry (in first trimester, PAPP-A and Free Beta HCG) and other maternal factors such as weight, whether or not she smokes and previous history of chromosomal anomalies are all considered when we calculate the 'adjusted risk'
Advanced maternal age, in my hospital at least, is considered as >35 years old. Nowadays the risk of complications is greatly reduced but there are some. Older mothers are statistically more likely to suffer with gestational diabetes, and breech presentation is more likely in older mothers, as is postpartum haemorrhage. The risk of stillbirth and premature birth is also slightly higher in older mothers.
This study gives some interesting stats on the above.
(Of course, just because these complications are possible doesn't mean they'll happen - my mum had my brother and I aged 21 and suffered pre-eclampsia, hypertension and delivered prematurely. She had my sister aged 36 and had a relatively easy time. So it's always possible to have a completely normal, event-free pregnancy!)