Can Breastfeeding During Pregnancy Cause Miscarriages?

Toddler breastfeeding
Getty Images/(c) Jaime Monfort

Everyone's heard the advice that "breast is best" for feeding new babies, but what happens when you get pregnant with a new baby while you're still nursing your older one? Is nursing during pregnancy safe?

Breastfeeding and Miscarriage

Although there are numerous conflicting opinions on the issue of breastfeeding during pregnancy, no research has ever found an increased risk of miscarriage in women who continue breastfeeding an older child during pregnancy.

In the past, doctors used to advise women to stop nursing when they became pregnant again. The concerns were that breastfeeding could deprive the developing baby of nutrients or stimulate uterine contractions (because breastfeeding causes increased oxytocin levels, which also can cause uterine contractions). But there is no conclusive evidence that this occurs and babies born to mothers who breastfed during pregnancy appear to be perfectly healthy.

The consensus is that it's up to the moms to decide whether to keep nursing during a new pregnancy. In a few high-risk conditions, such as placenta previa, doctors may advise increased caution but for most, nursing during pregnancy is probably safe.

What Does Cause Miscarriage?

About 3 of 4 miscarriages occur during the first trimester of pregnancy. These miscarriages are usually attributable to a problem with the fetus. Miscarriages that happen during the second trimester are often attributable to a health problem that the mother is experiencing.

In women aged 30 years or fewer, about 1 of 10 pregnancies end in miscarriage. This estimate doubles among women aged 35 to 39 to 2 of 10 pregnancies resulting in miscarriage.

First-Trimester Miscarriage

About 2 of 3 first-trimester miscarriages are due to chromosomal abnormalities in the fetus. Chromosomes contain all our genetic information in the form of genes. A fetus with an abnormal number of chromosomes can either have too many or too few chromosomes. Often, when there are chromosomal abnormalities, the fetus doesn't have the needed information to develop properly and miscarriage results.

Just because a mother experiences miscarriage due to chromosomal abnormalities of the fetus once does not necessarily mean that the problem will happen again. Furthermore, a miscarriage attributable to chromosomal abnormalities doesn't mean that either the mother's or father's chromosomes are faulty.

Aside from chromosomal abnormalities, miscarriage during the first trimester can also occur because of the following:

  • Placental problems (the placenta nourishes the fetus)
  • Smoking
  • Drug use
  • Obesity
  • Alcohol use

Second-Trimester Miscarriage

As mentioned above, miscarriage during the second trimester is often attributable to underlying health conditions that the mother is experiencing including the following:

Certain infections experienced by the mother may also increase the risk of miscarriage. These infections include the following:

  • Syphilis
  • Chlamydia
  • Rubella
  • Gonorrhea
  • HIV
  • Rubella
  • Food poisoning (listeriosis, toxoplasmosis, and salmonella)

In addition to chronic health conditions and infection, second-trimester miscarriage can also be attributed to the following:

What Doesn't Cause Miscarriage?

As we've already mentioned, breastfeeding during pregnancy is an unlikely reason for the miscarriage. Here are some other factors that don't cause miscarriage:

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