Huge
My son came home with nits when I was pg with dd2.
We had to treat whole family with potion stuff but was told not safe when pg. GP suggested conditioner & comb, but my hair is v long & thick so impossible.
I found this on Bounty web site which is safe when pg.
Mix 15 drops of eucalyptus oil & 15 drops of tea tree oil with 35 ml of vegetable oil.
Leave on hair for 1/2 hour then wash off. Repeat next day then a week later.
I got the oils from Boots.
It is also worth drying hair with hair dryer on hottest setting as the heat kills the lice.