Merck KGaA's Healthcare CEO Belén López said China's two-child policy was a major driver of the drugmaker's fertility segment sales for the third quarter and affirmed the sustainability of growth in the business.

"[The policy] is driving the market farther, but we have always been growing above the market in these geographies. So we see fertility as a significant contributor to our growth," López said on the company's Nov. 14 earnings call. She added that the company aims to deliver mid-single-digit growth by 2020.

López's response was prompted by a question regarding the sustainability of growth in the segment given that Chinese people will stop using the company's products after they have their second child.

During the third quarter, the German drugmaker's fertility product line booked net sales of €298 million, up 13.4% year over year from €263 million a year earlier.

While López admitted that China is the company's most important contributor in terms of the fertility segment, the healthcare head also said Merck is seeing considerable growth in other markets, noting that "the business is resilient in the U.S."

However, the company's fertility products have been taking a big hit in sales in Europe due to biosimilars, which are lower-cost copies of biologic medicines.

Mavenclad remains 'primary focus' of MS franchise in U.S.

Merck's pre-exceptional earnings for the third quarter totaled €963 million, down 5.9% from €1.02 billion a year ago. However, the company saw its healthcare sales grow 9.9% year over year to €1.60 billion.

Along with fertility, the company's third-quarter growth in healthcare was driven by the launches of multiple sclerosis drug Mavenclad and cancer drug Bavencio. The two therapies combined contributed €45 million in sales for the quarter.

"On Mavenclad, we are really meeting our expectations. As I mentioned before, the launch is on track. Today, the drug is already approved in 40 countries and is already reimbursed in the majority of those. So the launches are progressing well, not only in Germany, but also in major markets," López said.

The therapy was recommended by the U.K.'s National Institute for Clinical Excellence for use under the National Health Service in November 2017.

Meanwhile, Merck's other multiple sclerosis drug Rebif has been seeing a decline in sales due to competition in the U.S. and EU. The therapy, despite being one of the drugmaker's most profitable products, saw its net sales fall year over year to €363 million from €389 million.

López said the company is not moving all of its resources from Rebif to Mavenclad, but noted that the focus of the MS franchise will be behind Mavenclad.

"Mavenclad is going to be a primary focus of this franchise in the U.S.," López said.