Hooton, 42, who already has an eight-year-old daughter called Lily, with Lucas, said the couple have been desperately trying to expand their family, but had struggled to conceive.
"We’d just started going down the fertility route and were only three months into that when it happened without any intervention."
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Hooton plays Sam Dingle in Emmerdale
Hooton said Lucas had undergone a hysterosalpingogram, which is an x-ray technique used to examine the uterus and fallopian tubes to see if there are any blockages which could prevent eggs passing down the tubes to the womb and so stop pregnancy occurring.
Hooton said that a couple of weeks after the test Lucas fell pregnant.
The couple, who got engaged in 2010, said they had long hoped to have a sibling for Lily.
However Lucas admitted their struggle to conceive was a very "frustrating" time and she praised her fiancé for being supportive.
"I’m a worrier and I get stressed so he definitely helped me through it more than I helped him," she said. "He’s my rock."
The magic nutrient: Vitamin B6.This is one of the most important vitamins in aiding conception as it regulates the hormones. A B6 deficiency can lead to irregular menstruation and can also lead to poor egg and sperm development. (credit:Getty Images)
Asparagus(02 of10)
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The magic nutrient: Folic acid.Studies have found that folic acid can help reduce the risk of ovulatory failure. Women are also strongly advised to take folic acid supplements when trying to conceive. (credit:Getty Images)
Shellfish(03 of10)
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The magic nutrient: B12.Studies have suggested a link between B12 deficiency and abnormal oestrogen levels that may interfere with implantation of the fertilised egg. B12 may also help to strengthen the endometrium lining in egg fertilisation, decreasing the risk of miscarriage. (credit:Getty Images )
Eggs (04 of10)
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The magic nutrient: Vitamin D.A study by Yale University took Vitamin D measurements from 67 infertile women and found that only 7% of them had normal vitamin D levels, while the other 93% had either insufficient of clinical deficiency. They also found that none of the patients with PCOS had normal vitamin D levels. (credit:Getty Images)
Almonds(05 of10)
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The magic nutrient: Vitamin E.Studies suggest vitamin E can improve sperm health in men. A deficiency of vitamin E has also been linked to infertility in female rats. If you’re not convinced that an experiment with rats is evidence enough, it's also an antioxidant that helps to protect sperm and egg DNA. (credit:Getty Images)
Citrus fruit(06 of10)
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The magic nutrient: Vitamin C.A study in which infertile men were given 1,000mg of vitamin C twice daily, found that their sperm count and motility (their ability to move properly towards an egg) were improved. The vitamin is also said to improve hormone balance in women. (credit:Getty Images)
Tofu(07 of10)
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The magic nutrient: Iron.According to fertility expert, Hethir Rodriguez, “Studies have shown that women who do not get sufficient amounts of iron may suffer lack of ovulation and possibly poor egg health, which can inhibit pregnancy at a rate 60% higher than those with sufficient iron stores in their blood.” (credit:Getty Images)
Salmon(08 of10)
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The magic nutrient: Selenium.This mineral produces antioxidants that protect the eggs and sperm from free radicals. It can help prevent chromosome breakage, which is known to cause birth defects and miscarriages. Research also suggests that selenium may also make sperm more fertile. (credit:Getty Images)
Peas(09 of10)
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The magic nutrient: Zinc.Increasing zinc levels in infertile men has been shown to boost sperm levels, improve the form, function and quality of male sperm and decrease male fertility. For women, a lack of zinc can lead to an imbalance of oestrogen and progesterone. (credit:Getty Images)
Mackerel(10 of10)
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The magic nutrient: Essential fatty acids.These are, um, essential, for a strong reproductive system in women. DHA, one of the fatty acids found in fish oil has a significant impact on sperm health. A fatty acid deficiency leads to an increase in cholesterol in the sperm membrane which prevents sperm from proper maturation. (credit:Getty Images)