When talking about breastfeeding in pregnancy, we come across contradictory messages that rarely have a scientific basis. This leads the mother or breastfeeding person to have doubts when planning a pregnancy during lactation or fears if she is already pregnant.

Lack of research on pregnancy during breastfeeding

The first thing to note is that scientific publications on the subject are notably absent. In addition, most of the publications that are less than 10 years old are literature reviews and therefore, there has been no basic research with robust results to be able to clarify the dilemma about the risks of lactation during pregnancy in a conclusive manner.

Is it safe to breastfeed during pregnancy?

In the scarce scientific literature, in general, it seems to be safe. There could be an increase in first trimester miscarriages, which are of difficult implantation when breastfeeding is exclusive and before 5 months of age of the breastfed baby.

This difficulty of implantation could be due to a luteal phase that is not yet well established due to both luteal and progesterone insufficiency, which are usually hormones that are activated a little later than estrogens when the menstrual cycle is established again during the time of lactation.

Some reviews point out that during the first 5 months after childbirth, while still exclusively breastfeeding, the possibility of a first-trimester miscarriage could be as high as 35%, while after this period, it would be around 15%, which is the same as in situation of a not breastfeeding. Therefore, breastfeeding does not increase the risk of spontaneous miscarriage.

The safety of breastfeeding during pregnancy has also been questioned because of the presence of oxytocin, which could be related to uterine contractions. We know that uterine oxytocin receptors develop during pregnancy. During the first months, they are usually not activated. In addition, other physiological situations, such as orgasms, can also activate oxytocin and have not been associated with an increased risk of miscarriage.

As the uterus develops in pregnancy, these receptors may begin to be activated, and occasionally, the pregnant woman may feel mild contractions during the feed at the breast that disappear spontaneously afterward.

In no case has breastfeeding been related to increased intrauterine death, low birth weight, or premature birth.

On the other hand, breastfeeding during pregnancy has not been related to an increase in gestational diseases such as hyperemesis gravidarum, preeclampsia, eclampsia, or cholestasis of pregnancy.

In their conclusions, research teams repeatedly mention the energy expenditure involved when breastfeeding and being pregnant at the same time and point out the need for further research to know whether, at a nutritional level, modifications should be made if breastfeeding and pregnancy coincide. Even so, the signs that could be a consequence of this nutritional restriction do not appear in the study, such as an increase in small-for-gestational-age (SGA) babies, babies with intrauterine growth restriction (IUGR), premature birth, insufficient weight gain of the pregnant woman, or an increase in iron deficiency or other nutrients.

Surely, this data indicates that breastfeeding during pregnancy is safe for both the unborn child and the pregnant woman.

Even so, more research on human lactation is always welcome.

What if fertility treatment is needed?

There is no research on breastfeeding in normal pregnancies, so when difficulties at the beginning of pregnancy come into the equation, the absence of research is even more noticeable. In addition, there is a context of significant impact on the mental health of the mother and family.

Dr. Gaggiotti and Dr. Alvaro, physicians specializing in Assisted Reproduction at the Fundació Puigvert-Hospital de Sant Pau in Barcelona, explain more about this topic in the article “Breastfeeding and Fertility Treatments.”

Breastfeeding during pregnancy

During pregnancy, lactation may change. Many women will notice, as the first symptom of pregnancy, some pain or discomfort in their nipples during suckling. This is a symptom that usually appears very early. If the breastfed child is old enough, it may also say that the milk tastes different.

Although sometimes there is a decrease in milk production from the first weeks of pregnancy, it is usually not until weeks 16-18 when there is a sharp drop in milk production. This is because, from that week on, the placenta begins to produce large amounts of estrogen. Placental lactogen, a hormone that is also secreted by the placenta, peaks between weeks 24 and 28 of pregnancy and also results in a decrease in milk production.

The pregnant woman will produce precolostrum and then colostrum, but probably in greater quantities than if there had been no lactation during the pregnancy.

As previously mentioned, when the pregnancy is advanced, it is likely that the woman notices mild limited contractions during suckling, but no link to an increased risk of prematurity could be established. However, an individual assessment of each case is essential.

Some children who are breastfed during pregnancy will wean spontaneously. The incidence of weaning is uncertain due to the lack of research. But it is probably higher if the child is smaller because it needs more milk.

When breastfeeding during pregnancy, it should be assessed whether maternal milk production is enough for the age of the breastfed child. If the infant is less than one year old, artificial formula milk supplementation may be necessary, especially if the pregnancy reaches 16 weeks during this first year. If the breastfed child is beyond one year of age or has already enough complementary solid food, supplementation may not be necessary.

Once the pregnancy is over, milk production will rise again so that there will be enough milk production for both children. This situation is called tandem breastfeeding. The mother needs to have the information to be able to manage this, as well as be informed on the possibility of breastfeeding aversion, which is an emotion that can appear when breastfeeding during pregnancy or tandem breastfeeding.

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