does not hurt your fetus or causes any harmful effect if it is done in healthy & hygienic way. Doing masturbation is good for health and pleasure if it is done in quite control.
Do weekly check up for assessment of pregnancy
and fetus well being. Continue Iron/Calcium tabs.
Maintain genital hygiene and wash properly after each masturbation/sexual activity. Don't use any chemical lubricant as it may cause irritation. Avoid stress