There is an increased prevalence of high Body mass index (BMI) all over the world.High BMI is shown to have an impact on the female reproductive system.It can contribute to both ovulatory and anovulatory subfertility.

Clomiphene citrate and Letrozole have been used for treatment of infertility.Both are used for induction of ovulation.

Clomiphene citrate is an estrogen receptor antagonist .It increases serum FSH and it has its limitation due to his antiestrogenic effect,it has an ovulation rate 70-80% but pregnancy rate is only 22% because of its anti-estrogenic effect on endometrium and poor cervical mucus (Legro RS et al.,2007) Letrozole is an aromatase inhibitor which inhibits the production of estrogen, which influences the action of the brain's hypothalamus and pituitary on the functioning of the ovaries by increasing FSH.Due to the antiestrogenic effect of clomiphene citrate,Letrozole can be used as an alternative.

The investigators are comparing the effect of both medications on the outcome of the induction of ovulation in women with high BMI.

This is a Randomized controlled trial .The researchers include160 women with BMI more than 30 who were suffering from subfertility for more than 2 years. The investigators will randomise them into 2 groups. Group A:They were prescribed 100 mg of clomiphene citrate from day 2-5 of the cycle for 5 days. Group B : They were prescribed 5 mg of Letrozole from day 2-5 of the cycle.

Vaginal ultrasound was performed on day 11 of the cycle, After at least one follicle reached 15 mm, The patient was encouraged to have sexual intercourse every other day for few days.The patients will have a midluteal progesterone level to confirm ovulation and will have a pregnancy test in 2 weeks if missed period. The researchers will compare the number of mature follicles, endometrial thickness on the day when there are mature follicles, occurrence of pregnancy, multiple pregnancies, and miscarriages .

Inclusion Criteria:

• Age: 18-45 years old.
• History of subfertility for 2 years.
• No previous IVF
• Intact tubes as evidenced by HSG or Hycosy
• Normal Sperm parameters according to WHO criteria.
• Ability to have regular intercourse during the ovulation induction phase of the study.

Exclusion Criteria:

• Age less than 18 years old or older than 45 years old.
• FSH> 15 mIU/ml
• Tubal factor of infertility
• Male factor of infertility
• Current pregnancy,abnormal uterine bleeding.
• History of use of hormonal contraception in the last 3 months.
• Untreated medical problems: thyroid disease,hyperprolactinemia or contraindication to pregnancy as uncontrolled diabetes or severe heart disease.
• Contraindications to clomiphene citrate: hypersensitivity to clomid.
• Contraindications to letrozole: hypersensitivity to letrozole .