Healthy, well-nourished women who breastfeed while pregnant don’t seem to increase their risk of delivering prematurely, miscarrying, or having a low-birth-weight baby, the authors of a new research review conclude.

But Gemma Lopez-Fernandez of Corporacio Sanitaria Parc Tauli in Barcelona, Spain, and colleagues write in the journal Women and Birth that more research is needed on the implications of nursing during pregnancy for mothers and children’s health.

While many women will decide to wean after getting pregnant, it is not uncommon for women to continue to nurse, Melissa Kotlen, an international board-certified lactation consultant based in New York, told Reuters Health in a telephone interview.

“If you’re healthy, you’re low risk, you’re not on bedrest, there’s really no problem with continuing to nurse while you’re pregnant,” Kotlen said. “Most of these moms end up tandem nursing once the baby’s born anyway.”

But even pediatricians and obstetricians can fall prey to unproven but common beliefs about nursing during pregnancy, Kotlen added, for example that nipple stimulation will trigger the release of oxytocin and bring on labor prematurely, or that nursing during pregnancy will deplete a mother’s nutritional stores.

To investigate these and other potential risks of breastfeeding in pregnancy, Lopez-Fernandez and her team reviewed 19 studies published between 1990 and 2015 and including a total of about 6,300 women.

They found some evidence that women who nursed during pregnancy gained less weight, had fewer fat reserves and lower levels of hemoglobin – the molecule in red blood cells that carries oxygen. But the reviewers note that most research on the issue was done in the developing world.

The investigators found no support for the idea that breastfeeding women were more likely to deliver prematurely or to miscarry. Evidence on the effects of nursing during pregnancy on fetal and infant growth, as well as on the growth of the nursing child, was mixed.

Mothers who become pregnant while nursing should not be overly concerned about their nutritional status, as long as they are eating and drinking well, Kotlen said. “Your body knows exactly what it needs to take in. If you’re pregnant and you’re nursing, your body is going to know very quickly you need to eat a little bit more and you need to drink a little more.”

Lopez-Fernandez was not available for an interview by press time.