To preface, Dr says I'm OK and my body type is more likely to gain in T3.
I began underweight (reason for having to do IVF) and gave up distance running (actually, all running) and hard workouts. Gained 7 lbs (4# in T1 and almost 3# in the past month) and I'm 17 wks. DH thinks I need to be eating more and showing by now. We see a little bump (looks more like I had a large dinner), but others don't yet. HB on home dopler is 150-160. I def eat when I'm hungry, though, right now, if I snack, it's mostly a nectarine or strawberries, and I'm usu a sweets person, so I throw a couple bites of ice cream in there daily. I guess some of the nagging and people saying I don't look pregnant is worrying me our 20 wk u/s will show development is slow.
Any advice? Thanks!
March 2011: Off Nuva, cycle back to "normal" for me: No periods since 15 years old.
June 2011:Provera&50 mg Clomid; Progesterone:0.7
July 2011:Provera&100mg Clomid; Progesterone:3.29
Met with RE:No Clomid response, begin injectables Sep
5 mg Letrozole and Ovidrel in the interim month. Cut out running (was a distance-runner), cycling, eliptical. Restricted to weight-training, walking, pilates. Brain MRI normal. Being physically over-stressed is the reason the body stopped producing prog.
Late Sep 2011: Menopur, Ovidrel,& IUI (10.10.11):BFN-Great injectable response: 2 mature, 6 near mature, many smaller; Problem: 9 cysts! Dr: IUI too uncontrolled for number of viable eggs & age. On to IVF! IVF ER 12.6: 37 mature eggs, 27 fertilized, froze all to avoid overstimulation; FET 1.22 (2 Grade 1)=BFN; FET 2.22 (3 Grade 2)=BFP! Beta 10dp3dt=291; 12dp3dt=644; HB 3.26!! 174 bpm: Vanishing twin almost completely absorbed 10wks

Re: Weight gain while beginning underweight
Before I got pregnant my BMI was at 19, I did not gain any weight until after 20 weeks, at my AS my belly was still very flat to the point that the tech joked with me about if we would find a baby in there. Baby measured in the 50th percentile at the scan.
I finally started looking pg not to much to eat between 24 and 25 weeks. You will show when you show, just think of the $ you will save only needing one season of maternity clothing!
~after 34 cycles we finally got our 2nd little bundle of joy~

My IF blog
I was underweight to start with too. I actually got pregnant somewhat unexpectedly because I hadn't been getting periods for a while so we weren't being careful. I managed to put on enough weight that I finally had ONE period and the next month I was pregnant. Anyway, I think at 17 weeks I had gained somewhere between 7 and 10 pounds. I had a little bump at that point, but it's perfectly normal not to show until later.
I have been using this chart, which someone else had posted on one of the bump boards a while back, to track my weight gain: https://www.indiacurry.com/women/pregcalc.htm
I have found it very useful because you can see whether you are on track to gain the minimum, average, or maximum amount of weight gain recommended based on your pre-pregnancy BMI. For women who start off underweight, the recommended range is 28-40 lbs. At 17 weeks, a gain of 7 lbs. puts you on track to gain 28 lbs. So, it looks like you are still within the normal range for this point in the pregnancy.
However, because you were underweight enough that it was affecting your ovulatory function, it is probably more important for you to make sure you don't gain too little. Whereas most women can afford to gain a little less than what's recommended without any negative outcomes, you don't have the same wiggle room. If you continue to gain steadily (about a pound a week), you will be just fine. But if that doesn't happen, you might want to make a more concerted effort to increase your calorie intake, whether you feel hungry or not.
If you were a runner, your abs are likely very strong. Strong abs = you don't show as soon. I didn't show with my first until I was 27 weeks, and that was only one that WE could see. Other people couldn't tell I was pregnant until 30 weeks.
I started out underweight as well. I gained about 30 lbs total, most of that being in the last trimester. If your doctor is not concerned, stop listening to idiots that have no idea what they are talking about.
i started underweight too. once i hit 22 weeks i finally gained a few pounds. it'll come be patient
start weight: 113
current: 125
I second that if your doctor isn't worried and the baby is measuring fine then I wouldn't worry about it. I've started out underweight with all my pregnancies. More so the first two.
With my first I only gained 12 lbs and 6 lbs and 3 oz of it was the baby. I didn't start till 6 months pregnant.
With the second my Dr. told me in the first trimester to put done weight on and I did. I gained 35 lbs by eating all my meals, snacking a lot and having desert in bed just about every night. I was showing by 12 weeks.