Here's a list of abbreviations/acronyms commonly used on parenting sites. Please feel free to add any I've missed!
AC - Assisted Conception
AF - Aunt Flo (periods)
AFAIK - as far as I know
AFK - Away from keyboard
AI - Assisted or Artificial Insemination
AID - Artificial Insemination with Donor Sperm
AIH - Artificial Insemination with husband's or partner's sperm
AP - Attachment Parenting
ART - Assisted Reproductive Technolgy
BBT - Basal Body temperature
BD - baby dancing (sex)
BFN - big fat negative (pregnancy test)
BFP - big fat positive (pregnancy test)
BTW - by the way
BW - blood week (periods)
CC - Controlled Crying
CD - cycle day
CIO - Cry it out
CM - cervical mucus
CVS - Chorionic Villus Sampling
DA - dairy allergy
DH, DW, DP, DS, DD, DF, DB, - dear husband, dear wife, dear partner, dear son, dear daughter, dear fiance, dear boyfriend
DSD, DSS - dear step daughter, dear step son
DI - Donor Insemination
DPO - days past ovulation
DXP - Dear ex partner - for those who still have a close and caring relationship with their former partner/parent of their children
EA - egg allergy
EBM - expressed breastmilk
EP - Ectopic Pregnancy
ER - Egg Retrival
ET - Embryo Transfer
EW or EWCM - Egg White or Egg White Cervical Mucus (description of cervical mucus at ovulation time)
FET - Frozen Embryo Transfer (or fertilised egg transfer)
FSH - Follicle Stimulating Hormone
FWIW - for what it's worth
FYI - for your information
*g* - grin
GIFT - Gamete Intrafallopian Transfer
GD - Gestational Diabetes
GYN - gynaecolgist
HPT - home pregnancy test
HTH - hope this helps
ICSI - Intracytoplasmic Sperm Insertion
IMO - in my opinion
IMHO - in my humble opinion
IUI - Intrauterine Insemination
IVF - In Vitro Fertilisation
IYKWIM - if you know what I mean
JMHO - just my humble opinion
LI - lacotce intolerance
LOL - laughing out loud
MCS - May contain swearing
MIL, FIL, BIL, SIL - mother, father, brother, sister-in-law
M/C - miscarriage
M/S - morning sickness
O - Ovulation
OB - Obstetrician
OHSS - Ovarian Hyper Stimualtion Syndrome
OI - Ovulation Induction
OPK - ovulation predictor test kit
OPU - Ovum (Egg) Pick Up
PA - peanut allergy
PG - pregnant
PCOS - Poly Cystic Ovarian Syndrome
POF - Premature Ovarian Failure
POF - Premature Ovarian Failure
PMSL - pi$$ myself laughing
ROFL - rolling on floor laughing
ROFLMAO - roll on floor laughing my a$$ off
SAHM - stay at home mum
S/B - Still birth
SD - step daughter
SS - step son
SO - significant other
TIA - thanks in advance
TMI - Too much information
TTC - trying to conceive
U/S - Ultrasound
WAHM - work at home mum
WCS - Will contain swearing
2WW - 2 week wait (wait after ovulation when TTC)
TYPING IN ALL CAPITALS SIGNIFIES YELLING/SCREAMING