{
  "id": "pregnancy-weight-gain",
  "version": "cb1ecb457c44",
  "status": "published",
  "name": "Pregnancy Weight Gain Calculator",
  "question": "How much pregnancy weight gain?",
  "summary": "Finds the recommended pregnancy weight gain for your pre-pregnancy BMI from the IOM 2009 guidelines, the range for your week of pregnancy, and whether your gain so far is within it.",
  "category": "health",
  "subcategory": "pregnancy",
  "url": "https://www.acalculator.org/health/pregnancy-weight-gain-calculator",
  "markdown": "https://www.acalculator.org/health/pregnancy-weight-gain-calculator.md",
  "kind": "schedule",
  "method": "BMI = weight before ÷ height²; the IOM range for the BMI category; by week w: 0.5 × w ÷ 13 to 2 × w ÷ 13 kg up to week 13, then 0.5 + (w − 13) ÷ 27 × (total low − 0.5) to 2 + (w − 13) ÷ 27 × (total high − 2) kg up to week 40.",
  "assumptions": [
    "The ranges are the Institute of Medicine 2009 guidelines, by pre-pregnancy BMI category (WHO cut-offs), read from the BMI shown to one decimal place.",
    "The week-by-week range is a straight line from nothing at conception to the IOM first-trimester gain (0.5 to 2 kg) at 13 weeks, then a straight line to the IOM total at 40 weeks.",
    "For twins the IOM gives only provisional total ranges, and none for an underweight BMI.",
    "This is general guidance, not medical advice; your provider may set a different goal."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "height": {
        "title": "Height",
        "description": "Your height.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": 1.2,
        "maximum": 2.2
      },
      "before": {
        "title": "Weight before pregnancy",
        "description": "Your weight before you were pregnant.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "mass",
        "minimum": 30,
        "maximum": 250
      },
      "now": {
        "title": "Weight now",
        "description": "Your weight today, to compare your gain so far with the range.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "mass",
        "minimum": 30,
        "maximum": 300
      },
      "week": {
        "title": "Week of pregnancy",
        "description": "Completed weeks of pregnancy, 0 to 42.",
        "type": "integer",
        "minimum": 0,
        "maximum": 42
      },
      "babies": {
        "title": "Babies",
        "description": "One baby or twins. For twins the IOM gives total ranges only.",
        "type": "string",
        "enum": [
          "one",
          "twins"
        ]
      }
    }
  },
  "outputs": {
    "total": {
      "label": "Recommended total gain",
      "description": "The IOM 2009 total gain for the pre-pregnancy BMI (and twins), as the IOM table writes it.",
      "format": "text"
    },
    "bmi": {
      "label": "Pre-pregnancy BMI",
      "description": "Weight before pregnancy ÷ height², to one decimal place.",
      "format": "number"
    },
    "category": {
      "label": "BMI category",
      "description": "The IOM (WHO) category of the pre-pregnancy BMI.",
      "format": "text"
    },
    "rate": {
      "label": "Weekly gain, second and third trimesters",
      "description": "The IOM weekly rate range for one baby after the first trimester.",
      "format": "text"
    },
    "soFarLow": {
      "label": "Range this week: from",
      "description": "The low end of the recommended gain by the week entered.",
      "format": "quantity",
      "unit": "lb"
    },
    "soFarHigh": {
      "label": "Range this week: up to",
      "description": "The high end of the recommended gain by the week entered.",
      "format": "quantity",
      "unit": "lb"
    },
    "gained": {
      "label": "Gained so far",
      "description": "Weight now minus weight before pregnancy.",
      "format": "quantity",
      "unit": "lb"
    },
    "status": {
      "label": "Your gain so far",
      "description": "Below, within or above the range for the week, compared in pounds to one decimal place.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "height": 1.651,
      "before": 63.502931800000006,
      "now": 68.94604024,
      "week": 20,
      "babies": "one"
    },
    "outputs": {
      "total": "25 to 35 lb (11.5 to 16 kg)",
      "bmi": 23.3,
      "category": "Normal weight",
      "rate": "0.8 to 1 lb (0.35 to 0.50 kg) a week",
      "soFarLow": 3.3518518518518516,
      "soFarHigh": 5.62962962962963,
      "gained": 5.443108439999996,
      "status": "Within the range for week 20"
    },
    "text": "With a pre-pregnancy BMI of 23.3 (Normal weight), the IOM recommends a total gain of 25 to 35 lb (11.5 to 16 kg)."
  },
  "examples": [
    {
      "given": {
        "height": 1.651,
        "before": 63.502931800000006,
        "now": 68.94604024,
        "week": 20,
        "babies": "one"
      },
      "expect": {
        "bmi": 23.3,
        "category": "Normal weight",
        "total": "25 to 35 lb (11.5 to 16 kg)",
        "rate": "0.8 to 1 lb (0.35 to 0.50 kg) a week",
        "soFarLow": 3.3518518518518516,
        "soFarHigh": 5.62962962962963,
        "gained": 5.443108439999996,
        "status": "Within the range for week 20"
      },
      "source": "Institute of Medicine 2009, Table S-1 (normal weight, 11.5 to 16 kg; first trimester 0.5 to 2 kg); week 20 on the line from week 13 to week 40; hand calculation in content.mdx"
    },
    {
      "given": {
        "height": 1.6,
        "before": 80,
        "now": 82,
        "week": 10,
        "babies": "one"
      },
      "expect": {
        "bmi": 31.3,
        "category": "Obese",
        "total": "11 to 20 lb (5 to 9 kg)",
        "soFarHigh": 1.5384615384615385,
        "status": "Above the range for week 10"
      },
      "source": "IOM 2009 Table S-1 (obese, 5 to 9 kg; 0.5 to 2 kg by the end of the first trimester); hand calculation in content.mdx"
    },
    {
      "given": {
        "height": 1.7,
        "before": 75,
        "week": 30,
        "babies": "twins"
      },
      "expect": {
        "bmi": 26,
        "category": "Overweight",
        "total": "31 to 50 lb (14 to 23 kg)"
      },
      "source": "IOM 2009 provisional twin guideline: overweight 14 to 23 kg (31 to 50 lb)"
    }
  ],
  "sources": [
    "Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: The National Academies Press; 2009. Summary, Table S-1, and the provisional guidelines for twins. https://doi.org/10.17226/12584",
    "Centers for Disease Control and Prevention. Weight Gain During Pregnancy (May 15, 2024). https://www.cdc.gov/maternal-infant-health/pregnancy-weight/index.html"
  ],
  "related": [
    "pregnancy-week",
    "pregnancy",
    "bmi"
  ],
  "changelog": []
}