My first child DS was born on 12.02.08
TTC since 02.2009
Diagnosed with PCOS 06.2010
Started Metformin 500mg 4x a day =2000mg 06.2010
One cycle Clomid on 08.2010
BFN 09.05.2010
Diagnosed with 21 Hydroxylase Deficiency 09.15.2010
Started Prometrium 10.01.2010
Saw a Genetic Counselor 10.14.2010
BFN 11.01.2010
Started 2.5mg Femara 1x a day 12.21.2010
BFP 01.27.2011
EDD 09.27.2011
First US scheduled 02.08.11 - EXCITED!
4th US and walk through for CVS procedure scheduled for 03.03.11
2nd child DD born on 09.14.11!
BFP 10.27.12 - unexpected/unplanned conception

EDD 07.12.13
CVS scheduled for 12.26.12
12.28.12 found out baby is a girl

expecting DD #2
Started bleeding on 12.28.12
Lost DD #2 due to no heart beat on 01/22/13 delivered naturally
01/24/13 D&C to remove placenta for not descending
Started 200mg Prometrium for 10 nights 02.22.13
Finished Prometrium on 03.03.13
Started 5mg Femara for 5 days on 03.04.13 BFP 05.03.13 EDD 01.07.14 3rd child DS born on 01.06.14! Surprise BFP 06.03.15 EDD 02.07.16
Re: Coughing ONLY at night, persistant sudden cough
DS had a cough like that start around 19 months. Took him to the dr and nothing wrong with him. He was only coughing at night and would wake him self up. It was horrible. It finally went away around 20.5 months. He never acted like anything was wrong either. We tried honey, vaporizor, vicks, and elevating him but nothing work. It just stopped one day. I wish I kenw how to help you.
I would ask your doctor if they would be comfortable with any sort of cough suppressant, or, a nebulizer before bed? Some pediatricians allow small doses of benedryl or even robitussen (very small doses) and either of those could help with the coughing, and also make her a little drowsy/less likely to wake.
I know some people are very anti-meds, but if you're open to all options this could be one. (especially if you feel like you've already tried everything else)
Another thought - when was the last time you changed your air filters and/or had your vents cleaned? Maybe she is reacting to dust/mold or something.
Also, are you running a humidifier?
My son had a night time cough starting at about 2 weeks of age. We ended up seeing a pediatric pulmonologist who did a BUNCH of tests. In the end, it was reflux causing the cough. He's been on Zantac for well over a year now and is doing great! No more cough.
They did think it was asthma at first. The symptoms can be VERY similar.
I wanted to add the things the pulmonologist was considering, just in case it would help.
Asthma
Reflux
Swallowing issues / dysphagia
Allergies
Structural abnormalities in the ENT system
Structural abnormalities in the GI system