The YHL for underweight or obese women was about 4.5 years, which was significantly lower than the normal group.

Frisch suggested that underweight women would also have impaired reproductive function owing to a lack of oestrogen produced in adipose tissue.

Both underweight and overweight women had a lower chance of becoming pregnant than women with normal weight, although this effect was greater for the obese than for the lean women.

Normal and underweight women should gain about two to four pounds a month.

Also, the ranges for underweight women carrying twins is unknown.

(The study also found that women of ordinary weight were more likely to get false positives than were underweight women.)

In short order, the modeling agencies that manage the most notoriously underweight women abruptly benched them.

For example, underweight women averaged 4.50 YHL compared to 4.92 for normal women, and the common standard deviation was 1.44.

Meanwhile, underweight women were also more likely to set their target pregnancy weight gain too low.

In addition, 51% of underweight women reported a target weight gain below the guidelines versus 10% of normal-weight women.