Can you Take Phentermine while Pregnant? (what happens?)

January 8, 2024 |

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This article will give you an insight into the use of phentermine in pregnancy and its potential effects on the baby.

Phentermine can effectively help you lose unwanted weight and get in shape, but its consumption during pregnancy comes with many suspicions.

Phentermine is contraindicated during pregnancy and may cause gestational diabetes in the mother-to-be. Likewise, it can lead to prenatal stroke, cephalic cysts, and neural tube defects in the unborn baby.

In the following sections, I have compiled a list of the possible impacts of phentermine on pregnancy, along with the guidelines about its usage from drug regulatory authorities and health officials.

You will also find case studies about the effects of this drug on the baby during the gestation period.

So, keep reading to find all the details.

How can Phentermine affect a pregnancy?

Phentermine can potentially harm the fetus and may result in abnormal pregnancy outcomes.

It is actually a methylated amphetamine, and this group of compounds has a bad reputation for their negative impact on pregnancy and infants.

This review paper on gynecology reports that clefting, cardiac anomalies, and fetal growth deficits were seen in newborns exposed to these compounds during gestation.

FDA has given it category X for pregnancy medication. This category includes those drugs whose effects are not studied in much detail, but many doubts are present regarding their safety.

That is why both the authority and gyne professionals recommend that women should have a pregnancy test every month when taking this supplement and immediately stop taking phentermine if pregnancy is diagnosed.

Phentermine has shown significant weight loss in both women who are pregnant as well as those who are not conceiving.

However, in pregnancy, weight loss is considered a risky deal. For pregnant women, a little weight gain is necessary as maternal tissues are growing and the fetus is developing into a healthy baby.

Besides that, nutritional requirements are also increased as you have to provide food for two individuals. So suppressing your appetite would not be a wise decision as you would never want to starve your baby.

This comparative study on complications of pregnancy suggests that weight loss during gestation is a risk factor. Due to this, mothers-to-be should avoid taking appetite suppressants.

Another study shows that weight loss in pregnancy increases the odds of cesarean delivery by 1.4 times and that of premature delivery due to small gestational age by up to 1.8 times.
Since the baby in the womb is much affected by physiological changes in the mother’s body, the effects of phentermine on systems other than the uterine will also distress the health of the baby.

Common side effects of phentermine include:

  • nervousness
  • excitability
  • nausea
  • constipation
  • insomnia
  • headache
  • dry mouth
  • palpitation
  • thirst

These symptoms can make Gravida feel very sick and will have a negative impact on her child.

Thus, I would recommend when conceiving; you should stay away from weight loss products and appetite suppressants like phentermine.

Also read: Can Phentermine Cause Miscarriage?

Can you take Phentermine while trying to get pregnant?

Yes, because the pregnancy rate is not affected by phentermine; however, it is not a recommended practice.

When we look at the research, only one paper is available on the effects of phentermine on pregnancy rates. And in this study, no significant difference was seen between the control group and the phentermine group.

However, FDA medication guidelines about pills containing phentermine suggest that women should use contraception consistently while taking these drugs.

FDA regulations state that Qsymia- a pill containing phentermine and topiramate can cause serious birth defects, including lip cleft or palate cleft. These defects onset very early in the pregnancy; that is why phentermine intake is usually forbidden if you are planning to have a baby soon.

While pre-conception weight loss will be helpful in pregnancy if you currently suffer from obesity, it is better to use natural methods like exercise or dietary changes rather than medicinal formulations.

What if I took Phentermine while pregnant?

It is potentially unsafe to use phentermine during pregnancy. Following are some negative offshoots of its usage that may affect pregnancy either directly or indirectly.

Gestational diabetes mellitus (GDM)

Research conducted in 2002 shows that the probability of developing diabetes during the gestational period is significantly increased for women who took phentermine during their 1st trimester.

A review paper submitted in 2019 indicates that gestational diabetes tends to increase the risk of obesity, impaired glucose metabolism, and cardiac disorders in both the mother and the baby.

If a mother develops diabetes when she is conceiving, her child is twice to eight-fold more likely to suffer from type-2 diabetes later in life than a woman who didn’t experience GDM.


Phentermine is also known by research to cause insomnia at moderate intensity.

If a pregnant woman is sleep-deprived, the physiology of the child in her womb and ease of delivery would be affected.

This study shows that lack of sleep during the gestation period may increase labor time and discomfort. It is also found to increase the rate of C-sections and preterm labor.


According to scientific reports, phentermine tends to induce symptoms of psychosis which usually fade away once the medication is stopped. The case study of a young Asian female who developed psychotic illness when she took phentermine to reduce weight sounds concerning.

Another review suggests that phentermine induces depression in some patients, but its effect on the central nervous system is comparatively lesser than other similar drugs.

Anxiety and depression during pregnancy can disturb the physical health of both the mother and the infant. According to our research, anxiety may lead to shorter gestation ages and poor neural development in the fetus.

Also read: Does phentermine affect birth control pills?

Will phentermine harm my unborn baby?

Phentermine may cause abnormalities in unborn babies like neural tube defects, fetal stroke, cephalic cysts, or an increase in head circumference.

The above-mentioned paper also reports that an increase in birth weight and head circumference is seen in babies whose mothers used phentermine in the first three months of gestation.

Further research is required to learn about its effects on pregnant women and their children. However, we found a case study that demonstrates its harmful tendency for the little one in the womb.

A baby girl with bilateral porencephalic cysts was born to a 24 years old healthy woman. It is suspected that a fetal stroke is responsible for this abnormality. The mother did not have any history of cardiovascular disease or diabetes, but she admitted that she used phentermine until the 28th week of pregnancy.

It is also suspected that drugs with phentermine can cause valvular dysfunction and pulmonary hypertension in young ones.

Moreover, perinatal exposure of children with amphetamine products puts them at risk of psychiatric co-morbidities and poor growth.

Wrap-Up on Phentermine and Pregnancy

Phentermine is an effective drug for weight loss, but it also has the potential to complicate pregnancy and cause developmental abnormalities in the unborn baby.

Therefore, you should not take phentermine during pregnancy as it increases the risk of gestational diabetes and may cause various other side effects like insomnia and digestive problems.

For the young one in the womb, phentermine imposes a risk of neural tube anomalies, formation of cephalic cysts, enlargement of head circumference, and perinatal stroke.

It is suggested that you avoid phentermine if you are conceiving or planning to do so. In either case, I would recommend you to contact your doctor and have a chat about any medication you plan to opt for.

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