Is diastasis recti a sure thing to happen with a twin pregnancy, even if abs were tight and weight was 122? or in subsequent pregnancies where mom is thin to normal weight prepregnacy.

Diastasis recti: Diastasis recti is the partial or complete separation of the rectus abdominis, or “six-pack” muscles, which meet at the midline of your stomach. It is very common during/following pregnancy esp multiples. The enlarging uterus stretches the muscles in the abdomen. Try consistent physical activity, weight management, and core strengthening exercises (including crunches) to prevent problems.

Diastasis Recti: One study found that around 60 % of women may experience diastasis recti during pregnancy or postpartum. REF: https://www.healthline.com/health/diastasis-recti#TOC_TITLE_HDR_1 . At age 43 your risk for this is increased (over 35) and because you are having twins. Subsequent pregnancies, having a short torso or being petite also increases risk.