Underweight while pregnant: 4 ways it can affect baby

Weight of the mother is important during pregnancy. If you are underweight during pregnancy, it may affect your baby.

Whether you are pregnant or not, weight matters. You should neither be underweight nor overweight to be healthy. If you are underweight and planning to get pregnant, you need to gain more weight. Being underweight can affect fertility, potentially reducing the likelihood of conceiving. If you do get pregnant, don’t be underweight. That’s because when a pregnant woman is underweight, it can pose risks to the well-being of the baby. When you plan to gain weight, make sure it is within a healthy range. This way you will be able to support the growth and development of your baby. Read on to know more about how being underweight during pregnancy can affect your baby.

How much should you weigh when you are pregnant?

During pregnancy, a woman’s weight can vary significantly depending on factors such as pre-pregnancy weight, height, and overall health. If before pregnancy you are underweight, that means your Body Mass Index (BMI) is less than 18.5 then you should gain 28 to 40 pounds, according to the US Centers for Disease Control and Prevention’s weight gain recommendation for women pregnant with one baby. And if you are pregnant with twins, gain 50 to 62 pounds, recommends the CDC.

A woman measuring waist
Being underweight can impact fertility. Image courtesy: Freepik

Is it harder to get pregnant if you are underweight?

When it comes to chances of getting pregnant, a woman’s weight plays a significant role. Here is a breakdown of how being underweight can impact fertility.

1. Menstrual cycle disruption

Irregular periods make it difficult to predict ovulation accurately, which is essential for conceiving. Without regular ovulation, the chances of getting pregnant may be significantly reduced, says obstetrician and gynaecologist Dr Archana Ramesh.

2. Hormonal imbalances

Low body weight can lead to decreased estrogen levels, which are crucial for the development and release of mature eggs during each menstrual cycle. Insufficient estrogen levels can disrupt the ovulation process, making it harder to conceive.

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3. Risk of pregnancy complications

Even if pregnancy occurs, being underweight during pregnancy increases the risk of complications such as preterm birth.

4. Nutritional deficiencies

Underweight women are at risk of nutritional deficiencies, including essential vitamins and minerals crucial for reproductive health. Nutrient deficiencies can negatively impact fertility by affecting hormone production, egg quality, and overall reproductive function.

How does being underweight during pregnancy affect the baby?

A 2015 study published in the Proceedings of the National Academy of Sciences found 42.2 percent of women in India to be underweight when they started their pregnancy journey.

Being underweight during pregnancy is not good, as it can have significant implications for both the mother and the baby, impacting various aspects of health and development.

1. Low birth weight

Babies born to underweight mothers are at higher risk of being born with low birth weight, which is associated with various health complications. Low birth weight babies may experience difficulties with temperature regulation, feeding and immune function, increasing the likelihood of hospitalisation and long-term health issues.

2. Preterm birth

Underweight pregnant women are more prone to delivering prematurely, before completing the full term of pregnancy (37 weeks). Preterm birth increases the risk of complications such as respiratory distress syndrome, jaundice and infections, as the baby’s organs may not be fully developed to function outside the womb, explains the expert.

A pregnant woman touching her belly
Underweight pregnant women may deliver babies with a weak immune system. Image courtesy: Freepik

3. Weak immune system

Underweight pregnant women may have compromised immune function, which can affect the baby’s immune system development. Babies born to underweight mothers may have weakened immune systems, making them more susceptible to infections and illnesses during childhood.

4. Nutritional deficiencies

Maternal undernutrition during pregnancy can result in inadequate nutrient supply to the developing fetus. Nutritional deficiencies in the womb can impair the baby’s overall health and increase the risk of conditions such as anemia, poor bone development, and organ dysfunction.

What should underweight women do to gain weight for pregnancy?

Underweight women preparing for pregnancy should focus on adopting a balanced and nutrient-rich diet to support healthy weight gain. This means increasing calorie intake by incorporating wholesome, calorie-dense foods such as nuts, seeds, avocados, healthy fats, lean proteins, whole grains, and dairy products into their meals. Consuming frequent, smaller meals throughout the day can also help in boosting calorie intake. Prioritise nutrient-dense foods rich in vitamins, minerals, and essential fatty acids for fetal development.

Gaining weight before pregnancy allows women who are underweight to achieve a healthier weight, improving their chances of conceiving and supporting a healthier pregnancy, says Dr Ramesh. It also provides an opportunity to optimise nutritional status and address any underlying health concerns before conception occurs.

Gaining weight during pregnancy is also essential for supporting the growth and development of the baby. Adequate weight gain during pregnancy is associated with better birth outcomes and reduces the risk of complications such as preterm birth and low birth weight.

The best approach is for women to strive for a healthy weight before conception and to continue to gain weight steadily throughout pregnancy.