Many studies of intrauterine insemination (IUI) have evaluated pregnancy rates based on sperm parameters, and most use total motile count (TMC) of five to 10 million as the minimum threshold for proceeding. However, there’s no consensus about that range.

Catherine E. Gordon, MD, formerly a fellow in the Center for Infertility and Reproductive Surgery at Brigham and Women’s Hospital, Mark Hornstein, MD, director of the Center, Irene Souter, MD, and Karissa Hammer, MD, of the Division of Reproductive Endocrinology and Infertility at Massachusetts General Hospital, and colleagues have published encouraging data for many patients with insemination TMC <10 million. Their report appears in the Journal of Assisted Reproduction and Genetics.

Methods

The team retrospectively studied 1,154 initial IUI cycles completed between May 2015 and September 2019 at the Brigham or Mass General. All cycles made use of a freshly produced semen sample.

The primary outcome was the clinical pregnancy rate, evidenced by ultrasonographic visualization of a gestational sac. A secondary outcome was the rate of live birth, defined as delivery after 24-week gestational age.

TMC Alone

Insemination TMC was stratified as <2 million, 2–5 million, 5–10 million, 10–20 million, or >20 million. Once the threshold of 2 million was reached, there was no significant difference between TMC strata in clinical pregnancy rate (CPR) or live birth rate (LBR) when only TMC was considered. There were no clinical pregnancies in cycles with TMC <2 million.

TMC and Maternal Age

Among women 38 to 40 years old, those with TMC >20 million had significantly higher CPR than those with TMC 10–20 million (25/142 vs. 0/12; P=0.01).

Of the 88 cycles in women >40 years old, only two resulted in pregnancy and live birth, and both patients had TMC >20 million.

TMC and AMH Group

In the group of women with anti-Müllerian hormone (AMH) levels 1.5–3.49 ng/mL, TMC >20 million was associated with higher CPR than TMC of 5–10 million (40/217 vs. 1/18; P=0.03).

Of the 239 cycles for women with AMH <1 ng/mL, only 16 resulted in live birth. 15 were with TMC >20 million, and one was with TMC of 10–20 million.

TMC and Stimulation Regimen

This study is the first to evaluate pregnancy rates in IUI according to both TMC and stimulation regimens. The CPR was higher for letrozole ovulation induction than for other regimens (clomid, gonadotropins, or natural cycles), but the difference was not significant.

The TMC category did not affect CPR and LBR with any stimulation regimen once it was >2 million.

TMC and Fertility Diagnosis

Among patients with combined male and female infertility and TMC <2 million, both CPR and LBR were significantly lower than for patients with TMC >20 million (P=0.02 and P=0.03, respectively).

Toward More Personalized Patient Counseling

Based on these results and data reported in figures and tables, patients can be counseled that:

• Patients with TMC <10 million but ≥2 million may wish to attempt IUI cycles before proceeding with in vitro fertilization (IVF), especially those who are younger and those with good ovarian reserve

• Taking only TMC into account, patients with TMC ≥2 million can expect a pregnancy rate of about 10%–15% and an LBR of about 10% per completed IUI cycle

• Older women with a very low ovarian reserve may have better outcomes with IVF than IUI if TMC is <10 million

• Patients with combined male/female factor infertility and very low TMC may have improved outcomes with IVF

• Patients with mild male factor infertility (TMC >5 million and <20 million) can expect an LBR of about 10% per cycle, and patients with ovulatory dysfunction can expect an LBR of 15% per cycle