According to Scientists, Boys are More Demanding Than Girls Even Before They are Born

According to research, knowing the sex of a baby during pregnancy can lead to better life chances. Pregnancies with male babies are more likely to have complications, possibly because they grow faster in the womb and need more nutrients and oxygen than the mother can provide through the placenta—the temporary organ that attaches to the uterine wall during pregnancy to support the growth and development of the fetus. After studying pregnancies in laboratory mice, scientists have found that the sex of a fetus, along with factors such as maternal obesity and stress, can affect the functioning of the placenta.

Knowing the Sex Could Help Identify Pregnancy Complications

About one in ten women experience pregnancy complications such as fetal growth restriction and preeclampsia—a life-threatening high blood pressure condition for both mother and baby—which are difficult to predict and treat. Research from the University of Cambridge suggests that creating individualized treatment plans and encouraging pregnant women to make lifestyle changes based on the sex of their unborn child could have lifelong health benefits for their children—and could spell the end of the tradition of waiting until the baby is born to find out whether it is a boy or a girl.

“Often, parents don’t want to know the sex of the baby because they want it to be a surprise. But knowing the sex would help determine whether a pregnancy is at higher risk than another, as we know that certain pregnancy complications, such as preeclampsia and fetal growth restriction, can occur more frequently in women carrying male babies than in women carrying female babies,” said Dr. Amanda Sferruzzi-Perri, a fellow at St. John’s College, who conducted the research with her team from the Department of Physiology Development and Neuroscience at the University of Cambridge at the Centre for Trophoblast Research.

“We don’t know for sure why this is, but it could be related to the fact that male babies grow faster in the womb. So it could be that their need for nutrients and oxygen, which are supplied by the mother via the placenta, is slightly restricted, meaning that the male fetus may not be getting everything it really needs to develop fully. They may be less resilient to stress or poor conditions during pregnancy than, for example, female fetuses, which have lower requirements.” Dr. Sferruzzi-Perri’s research team has published its findings in an article published in the journal Biology of Reproduction. A second study, written in collaboration with colleagues from institutions around the world, shows how maternal obesity alters the structures of the placenta and affects the growth of the baby, including changes based on the sex of the fetus. It was published in the journal “Acta Physiologica.”

The Way the Placenta Adapts Depends on Whether the Baby is Female or Male

Fetal growth depends on the function of the placenta, which requires energy from mitochondria—special compartments in our cells that help convert energy from food into energy that cells can use as fuel. The researchers found that in a normal mouse pregnancy, the placenta responds differently depending on whether it is supplying a female or male fetus, and that it functions better with the lightest female fetuses than with the heaviest male fetuses.

“The placenta has the amazing ability to change its shape and function,” said Dr. Sferruzzi-Perri. “This is evident at several levels, from the way cells form in the placenta to their genes and proteins to their mitochondria. All of this can change in response to different types of signals, whether it’s a mother eating a diet high in sugar and fat or a pregnancy involving sibling rivalry when more than one baby is on the way. However, in my opinion, the most novel aspect is that the way the placenta adapts appears to depend on whether the baby is female or male.” The studies show how important it is to develop gender-specific therapies for placental insufficiency and fetal growth disorders, as well as personalized lifestyle interventions or therapies for overweight pregnant women. The data the researchers obtained in the laboratory really showed them that the sex of the baby must be taken into account when monitoring a pregnancy. Therefore, treatments should perhaps be tailored to the sex of the baby.

Scientists already know that the risk of diseases such as type 2 diabetes and cardiovascular disease in men and women depends on gender—men tend to have a higher incidence of both diseases. The researchers investigated this in mice under certain environmental conditions, such as diet-induced obesity, which is very common worldwide, even in developing countries, where urbanization has given women easier access to foods high in sugar and fat than in the past. In the UK, more than half of pregnant women have a body mass index above the normal healthy range. This is concerning because maternal obesity increases the risk of pregnancy complications such as miscarriage, gestational diabetes, preeclampsia, and stillbirth. Abnormal birth weights can also lead to neurological developmental disorders and immune disorders in childhood, as well as obesity, diabetes, and heart disease in adulthood.

Improving Outcomes for Mothers and their Babies

More and more knowledge is being gathered about what should be measured in pregnant women, such as their baseline body mass index, growth, pregnancy weight, and even the sex of the fetus. Doctors routinely consider sex when looking at ultrasound images, as sex is an important factor in fetal growth. However, until now, it has not been clear how this can be determined and how it relates to the mother’s environment or the course of pregnancy. These studies therefore provide doctors with more information to make more informed decisions about the course of pregnancy.

Currently, there are very few options for treating women with pregnancy complications other than bed rest, nutritional counseling, or premature delivery, as medications can cross the placenta and affect the fetus’s highly sensitive organs. Scientists are now trying to develop treatments that only affect the placenta. These therapies would improve the functioning of the placenta, promote its development, and even increase energy production at the mitochondrial level to support fetal growth. Much of this basic research confirms experts’ belief that the placenta is essential for a healthy pregnancy and that the sex of the fetus plays an important role. By looking at the different types of genes, proteins, and cellular mechanisms, they could identify targets that act as biomarkers and are specifically targeted to the placenta to improve outcomes for mothers and their babies.