As of today, PF readers can start saving 15% on any purchase from Isabella Oliver Maternity or, from their contemporary wear collection, Isabella Oliver 365, when you use promotional “PFSPRING” at checkout. I have been singing the praises of Isabella Oliver maternity since I first started this blog two and half years ago.  But if you haven’t been part of my early audience (which was wholly comprised of people related to me and sex spammers from Russia), you may have missed out on some of my recommendations.  The good think about IO is that while they introduce new and fun styles every season, they also know what works and continue to bring back their tried and true maternity styles season after season.  The colors may change, but the fit–the most important part of maternity fashion–stays the same.

So in honor of the start of this Spring 2010 promotion, below are the basic spring maternity items you simply must buy from IO.  Don’t worry, I am working with a budget here–even if you buy every item below and use the PF promotion, you won’t spend more than USD $500. These pieces will be the crux of your maternity wardrobe and you’ll have them forever.

1. First of all, you need to buy one of IO’s signature Ruched Camisoles or Ruched Tank Tops.  You will come to depend on these tops as you increasingly need to “layer” and not only are they made from thick, durable cotton, but they have built-in shelf bras.  You’ll still have to wear a bra, but the extra support is nice during the day and they are absolutely ideal to sleep in.  Keeping our budget in mind, I’d opt for the camisole if you are less busty, but go for the tank if you are more well-endowed, as it does have nice, wide straps. The cami is USD $55 here and the tank top is USD $69 here.

2. Don’t even stop to think about it and immediately buy yourself a pair of the Garbo trousers in black here for USD $149.  These pants are simultaneously flattering and incredibly forgiving.  You can wear them out at night with a dressy blouse, to the office, or you can wear them to Starbucks with your flats and a T-shirt. I bought them when I was pregnant with the twins and I bought them again during my most recent pregnancy after I clumsily tore them with my heel.

3. Every pregnant woman needs a black wrap dress and Isabella Oliver’s Tie Knot Dress hits all the requirements for the go-to maternity wrap dress.  The dress is knee-length and has 3/4 sleeves, making sure pregnancy’s dreaded “problem areas” are well-covered. The sash is quite long so you may easily tie the dress in the front, on the side, or in the back.  It is machine washable.  Best of all, it is not a real “wrap dress,” i.e., it actually slips over your head so there is no danger of it “unwrapping” when you least expect it.  It is available here in black and indigo for USD $179.

4. Calculating with our PF discount, we still have about $175 to spend and I, as expected, will be going just a wee bit over budget by insisting that you buy the IO Trapeze Trench. If you are pregnant, you really must buy a maternity coat from Isabella Oliver.  IO has always impressed me in its recognition that pregnant women need maternity coats.  They don’t need empire-waisted coats or roomy coats or coats without buttons–they need real honest-to-goodness coats that are designed for people with small bodies but enormous bellies.  The Trapeze Trench comes in tan and white and couldn’t be more on-trend this spring.  Please don’t try to make it to summer in your non-maternity trench coat.  It won’t button and it will just barely tie and it just won’t look very nice.

There you have it.  My must-have IO list for just about USD $600 when combined with your PF discount.  I own all of these pieces, I’ve worn them for years, and I still have them all.  They’d be the first items I’d go looking for if need be.  You can’t go wrong with any of them, happy shopping and enjoy the discount!