Pregnancy Calculator

Pregnancy is a term used to describe a woman's condition over a period of roughly 9 months, during which one or more babies develop inside her. Childbirth usually happens about 38 weeks after conception, or around 40 weeks after the last menstrual period. The World Health Organization defines a normal pregnancy as lasting between 37 and 42 weeks. During a person's first OB-GYN visit, the doctor will typically give an estimated date (based on a sonogram) for when the child will be born, also called the due date. The due date can also be estimated from the last menstrual period.

While the due date can be estimated, the actual length of a pregnancy depends on various factors, including age, the length of previous pregnancies, and the mother's weight at birth. However, there are still more factors affecting natural differences in pregnancy terms that are not well understood. Studies have shown that fewer than 4% of births happen on the exact due date, 60% happen within a week of the due date, and almost 90% happen within two weeks of the due date. So while it is reasonable to be fairly confident that a baby will be born within about two weeks of the due date, it is currently not possible to predict the exact day of birth with certainty.

Pregnancy can be detected either by using pregnancy tests or by the woman herself noticing a number of symptoms, including a missed menstrual period, higher basal body temperature, fatigue, nausea, and more frequent urination.

Pregnancy tests work by detecting hormones that act as biomarkers for pregnancy. They include clinical blood or urine tests that can detect pregnancy from six to eight days after fertilization. Clinical blood tests are more accurate and can detect exact amounts of the hormone hCG (which is only present during pregnancy) earlier and in smaller quantities, but they take more time to evaluate and are more expensive than home pregnancy urine tests. A clinical urine test is also possible, but it is not necessarily more accurate than a home pregnancy test and can potentially cost more.

There are a number of factors that need to be considered during pregnancy, many of which depend heavily on the individual's situation, such as medication, weight gain, exercise, and nutrition.

Taking certain medications during pregnancy can have lasting effects on the fetus. In the U.S., drugs are classified into categories A, B, C, D, and X by the Food and Drug Administration (FDA) based on potential benefits versus fetal risks. Drugs that have positive benefits for the mother with low risk to the fetus are classified as category A, while drugs with proven, significant fetal risks that outweigh potential benefits to the mother are classified as category X. A person who is pregnant should consult their doctor about any medications they plan to use during pregnancy.

Weight gain is a largely unavoidable and necessary part of pregnancy that varies between people. It affects many aspects of fetal development, such as the weight of the baby, the placenta, extra circulatory fluid, and fat and protein stores. Weight management deserves attention because gaining too little or too much weight can have negative effects for both mother and fetus, including the need for a cesarean section (C-section) and gestational hypertension. While the values vary between women, the Institute of Medicine recommends an overall pregnancy weight gain of 25–35 pounds for women considered "normal" weight (BMI 18.5–24.9), 28–40 pounds for those considered underweight (BMI < 18.5), 15–25 pounds for those considered overweight (BMI 25–29.9), and 11–20 pounds for those considered obese (BMI > 30). Our Pregnancy Weight Gain Calculator is based on the Institute of Medicine recommendations.

Studies indicate that aerobic exercise during pregnancy helps to improve or maintain physical fitness and may possibly decrease the risk of C-sections. Although it varies between women, regular aerobic and strength-conditioning exercise is often recommended for pregnant women, and women who exercised regularly before pregnancy and who have uncomplicated pregnancies should be able to continue high-intensity exercise programs. The American College of Obstetricians and Gynecologists suggests that, given an uncomplicated pregnancy, fetal injuries are unlikely to occur as a result of exercise. Nevertheless, caution is advised, and a pregnant woman should consult their doctor if any of the following symptoms appear: vaginal bleeding, shortness of breath, dizziness, headache, calf pain or swelling, amniotic fluid leakage, decreased fetal movement, preterm labor, muscle weakness, or chest pain.

Nutrition during pregnancy is especially important for the health of the mother and baby. Pregnancy requires different nutritional considerations than a person would have in a non-pregnant state because of increased energy and specific micronutrient requirements.

Certain vitamins, such as Vitamin B9 (also known as folic acid), can help decrease the risk of certain defects, while other nutrients, such as DHA omega-3, which is necessary for proper brain and retinal development, cannot be produced efficiently by infants and can only be obtained through the placenta during pregnancy or in breast milk after birth. There are many other micronutrients that support proper fetal development, and there are countless sources of information on what pregnant women should or shouldn't eat or do. All of this information can be difficult to sort through and can vary from person to person. Pregnant women should consult their doctors and/or a dietitian to help determine the best course of action for their own specific needs.